Invasive Non-Native Species: Background and Issues for Congress

Report for Congress
Invasive Non-Native Species:
Background and Issues for Congress
Updated November 25, 2002
M. Lynne Corn, Eugene H. Buck,
Jean Rawson, Alex Segarra, and Eric Fischer
Resources, Science, and Industry Division

Congressional Research Service ˜ The Library of Congress

Invasive Non-Native Species:
Background and Issues for Congress
For the first few centuries after the arrival of Europeans in North America,
plants and animals of many species were sent between the two land masses. The
transfer of non-natives consisted not only of intentional westbound species ranging
from pigs to dandelions, but also intentional eastbound grey squirrels and tomatoes.
And for those centuries the remaining non-native species crossing the Atlantic
uninvited and often unwelcome, were ignored if they were noticed at all. National
focus on non-native species arose in the 19th Century, primarily over losses in
agriculture (due to weeds or plant diseases), the leading industry of the time. A few
newly-arrived non-natives, and new estimates of adverse economic impacts
exceeding $100 billion annually, have sharpened that focus.
Very broadly, the unanswered question regarding non-native species is whose
responsibility is it to ensure economic integrity and ecological stability in response
to the actual or potential impacts of non-native species? As this report shows, the
current answer is not simple, and may be “no one.” It may depend on answers to
many other questions: Is the introduction deliberate or accidental? Does it affect
agriculture? By what pathway does it arrive? Is the potential harm from the species
already known? Is the species already established in one area of the country?
Finally, if the answers to any of these questions are unsatisfactory, what changes
should be made?
The specific issue before Congress is whether new legislative authorities and
funding are needed to address issues of non-native species and their increasing
economic and ecological impacts. Such legislation could affect domestic and
international trade, tourism, industries dependent on bringing in non-native species,
those dependent on keeping them out, and finally, the variety of natural resources
which have little direct economic value and yet affect the lives of a broad portion of
the public.
In the century or so of congressional responses to harmful non-native species,
the usual approach has been an ad hoc attack on the particular problem, from impure
seed stocks to brown tree snakes on Guam. A few notable attempts have begun to
address specific pathways (e.g., ship ballast water), but no current law addresses the
general concern over non-native species and the variety of paths by which they enter
this country. A 1998 Executive Order takes a step in bringing together some of the
current authorities and resources to address a problem that has expanded with both
increasing world trade and travel and decreasing transit time for humans and cargo.
Bills have been introduced on this subject in the 105th, 106th, and 107th Congresses.
This report compares an approach based on a species-by-species assessment, vs.
one based on pathways of entry. It also assesses the choice of an emphasis on
prevention vs. post hoc control and intra-state quarantine. It describes existing
federal laws and federal agency roles, federal interagency cooperation, and the federal
interaction with state governments. Finally, it outlines effects, costs, and issues
surrounding 47 selected harmful non-native species.

Overview and Current Status.........................................1
The Size of the Threat..........................................1
Dollar Impacts................................................1
Major Laws and Executive Order.................................3
Executive Order 13112.....................................4
Preliminary Options for A Complex Problem........................4
Predicting an Invasion: Black and White?..........................5
Threat of Harmful Non-Native Species.................................7
Numbers of Non-Native Species in the United States..................9
A Brief History of Introductions.................................10
Geographic Origins of Non-Native Species.........................11
Pathways of Invasion..........................................12
Basic Methods of Pest Prevention and Control......................14
Baits and Attractants......................................16
Traps ..................................................16
Fumigants, Repellents, and Barriers Designed for Confined Spaces..16
Herbicides and Pesticides..................................17
Biological Control........................................18
Bounties and Commercial Exploitation........................19
Cultivation Control.......................................19
Mechanical Removal......................................19
Site Removal............................................19
Unusually Susceptible Habitats..................................20
Available Estimates of Costs and Impacts..........................21
Industries That Benefit from Non-native Species....................23
Harm to the Natural Environment: Diffuse Responsibilities............24
Federal Laws....................................................25
Lacey Act...................................................25
Animal Damage Control Act....................................26
Federal Seed Act.............................................26
National Environmental Policy Act of 1970 (NEPA).................27
Endangered Species Act (ESA)..................................28
Federal Noxious Weed Act.....................................29
Nonindigenous Aquatic Nuisance Prevention and Control Act..........29
National Invasive Species Act...................................30
Alien Species Prevention and Enforcement Act of 1992 (ASPEA)......32
Wild Bird Conservation Act of 1992 (WBCA)......................32
Hawaii Tropical Forest Recovery Act of 1992......................32
Plant Protection Act of 2000....................................33
Executive Order 13112........................................34
Agency Responsibilities:
Programs and Implementation...................................36
Interagency Efforts............................................36
National Invasive Species Council...........................36

Federal Interagency Committee for Management of Noxious
and Exotic Weeds (FICMNEW).........................39
Department of Agriculture......................................39
Agricultural Research Service (ARS).........................39
Animal and Plant Health Inspection Service....................40
Cooperative State Research, Education, and Extension Service
(C S R EES ) ..........................................41
Economic Research Service (ERS)...........................41
Farm Service Agency (FSA)................................42
Forest Service (FS).......................................42
Natural Resources Conservation Service (NRCS)................42
Department of Commerce......................................42
National Oceanic and Atmospheric Administration (NOAA).......42
National Sea Grant College Program..........................43
Department of Defense........................................44
Army Corps of Engineers..................................44
Department of the Interior......................................44
Bureau of Indian Affairs (BIA)..............................44
Bureau of Land Management (BLM)..........................45
Bureau of Reclamation (BOR)...............................45
Fish and Wildlife Service (FWS).............................45
Geological Survey (USGS).................................46
National Park Service (NPS)................................46
Office of Surface Mining Reclamation and Enforcement (OSM)....47
Department of State...........................................48
Department of Transportation...................................48
Coast Guard.............................................48
Federal Aviation Administration (FAA).......................48
Federal Highway Administration (FHwA).....................49
Executive Office of the President................................49
Council on Environmental Quality (CEQ)......................49
Office of Science and Technology Policy (OSTP)...............49
Office of the United States Trade Representative (USTR).........49
Independent Agencies.........................................49
Environmental Protection Agency............................49
National Science Foundation................................50
Smithsonian Institution....................................50
State Efforts.................................................50
International Efforts...........................................51
Coverage of Laws or Policy: Actions and Approaches....................55
Federal Agency Actions: A Patchwork............................56
Interaction of State and Federal Programs..........................58
Approaches to Regulation: Species-by-Species vs. Pathways...........58
A Few Legislative or Policy Options..............................59
A Gallery of Harmful Non-Native Plants and Animals....................63
Microorganisms ..............................................63
Whirling Disease, Myxobolus cerebralis.......................63
Plants ......................................................63
Leafy Spurge, Euphorbia esula..............................64

Spotted, Diffuse, and Russian Knapweed, Centaurea maculosa,
C. diffusa, Acroptilum repens, and Yellow Starthistle,
Centaurea solstitialis..................................64
Melaleuca, Melaleuca quinquenervia.........................65
Water Hyacinth, Eichhornia crassipes........................65
Salt Cedar, Tamarix (several species).........................65
Hydrilla, Hydrilla verticillata...............................65
Cordgrass, Spartina sp.....................................66
Caulerpa, Caulerpa taxifolia................................66
Arthropods: Insects...........................................67
Formosan Termite, Coptotermes formosanus...................67
Imported Fire Ants, Solenopsis invicta and S. richteri............68
Argentine Ant, Linepithema humile...........................68
Africanized Honeybee, Apis mellifera scutellata................69
Asian Longhorned Beetle, Anoplophora glabripennis............69
Asian Tiger Mosquito, Aedes albopictus.......................70
Mediterranean Fruit fly, Ceratitis capitata.....................71
Other Arthropods.............................................72
Honeybee Mites, Acarapis woodi and Varroa jacobsoni..........72
European Green Crab, Carcinus maenas.......................72
Chinese Mitten Crab, Eriocheir sinensis.......................73
Rusty Crayfish, Orconectes rusticus..........................73
Spiny Water Flea, Bythotrephes cederstroemi...................74
Mollusks ....................................................74
Zebra Mussel, Dreissena polymorpha.........................74
Brown Mussel, Perna perna................................74
Asian River Clam, Corbicula fluminea........................75
New Zealand Mud Snail, Potamopyrgus antipodarum............75
Vertebrates ..................................................75
Sea Lamprey, Petromyzon marinus...........................75
Alewife, Alosa pseudoharengus.............................76
Round Goby, Neogobius melanostomus.......................76
European Ruffe, Gymnocephalus cernuus......................77
Common Carp, Cyprinus carpio.............................77
Walking Catfish, Clarias batrachus..........................77
Snakeheads, Channidae....................................77
Rainbow Trout, Oncorhynchus mykiss........................78
Lake Trout, Salvelinus namaycush...........................78
Coqui, Eleutherodactylus coqui..............................78
Brown Tree Snake, Boiga irregularis.........................79
Indian Mongoose, Herpestes auropunctatus....................79
Nutria, Myocastor coypus..................................80
Appendix A: List of Acronyms......................................81
Appendix B: Federal Agency Funding for Invasive Species...............83

List of Figures
What’s In A Name?................................................3
U.S. As A Source of Non-Native Species..............................12
Homeland Security and Invasive Species..............................36
List of Tables
Estimated Numbers of Non-Native Species in the United States............10

Invasive Non-Native Species:
Background and Issues for Congress
Overview and Current Status
The Size of the Threat
Brown tree snakes from the western Pacific threaten power utilities and
communications on Guam and the Northern Marianas, and seem ready to invade
Hawaii and harm its enormous tourism industry. Zebra mussels from eastern Europe
clog intakes for urban water supplies and nuclear power plants in the Great Lakes and
the Mississippi basin. Formosan termites devastate living trees and historic buildings
in New Orleans’ French Quarter. Leafy spurge slashes the forage value of western
grazing land, thereby creating precipitous drops in land value. Voracious snakehead
fish from China appear in a pond in Maryland, precipitating drastic measures by state
officials to keep them from spreading and destroying many of the region’s freshwater
To continue with a full list of the damaging effects of harmful non-native plants
and animals risks sounding like hyperbole. Only in fairly recent years have many
people realized that various areas of the country share problems that are similar in
outline if not in detail. Impacts have been particularly severe on agriculture. The
globalization of trade, the increased speed of travel, the massive volume of cargo
shipments, and rising tourism all combine to increase the chance of more accidental
introductions. Moreover, trade in exotic plants and animals that would have been
impractical when voyages took days or weeks, now becomes practical when shipment
times are only a fraction of that. Some of the species in the horticulture and exotic
pet trades may escape or be released in the wild by accident or when owners tire of
All 50 states and all of the territories have at least some non-native plants and
animals. A few (e.g., Hawaii, Florida, Louisiana, Great Lakes states, California)
have so many harmful non-natives as to cause major ecological and economic
damage to a variety of locations and industries. Problems with terrestrial non-native
species tend to be more severe in the southern half of the country in terms of total
numbers of non-native species. Aquatic invasives have created more evenly
distributed problems.
Dollar Impacts
Estimating the total economic impact of harmful non-native species is extremely
difficult. No federal agency accumulates such statistics comprehensively. One

widely cited estimate put damage at $123 billion annually.1 Including cost of control,
damage to property values, health costs, and other factors, the following are the costs
of selected species:2
!Leafy spurge (plant) — over $100 million annually
!Purple loosestrife (plant) — $45 million annually
!Formosan termite — $1 billion annually (including several hundred
million dollars in New Orleans alone)
!Fire ant — about $2 billion annually (including $300 million in
Texas alone)
!European green crab — about $44 million annually
!Zebra mussel — More than $750 million over 10 years (only for
cleaning water intake pipes, filtration equipment, power generating
equipment, etc., but not damage to docks, recreational or
commercial boats, or other problems)
!Asian river clam — $1 billion annually
!Sea lamprey — $10-15 million annually for control only
!Brown tree snake — $1 million annually on Guam in power outages
Many impacts would be extremely difficult to measure in monetary terms. The
West Nile virus has had a severe impact on populations of some wild birds, which
are a major focus of recreation for millions of Americans. The introduction of lake
trout into Yellowstone Lake (see Gallery, below), for example, is likely to have
profound effects on populations of native cutthroat trout and, as a result, on grizzly
bears, bald eagles, and other species. The presence of honeybee mites (see Gallery)
is more problematic. On the one hand, crops pollinated by honeybees (itself a non-
native species) will be more difficult to raise. On the other, species of native bees
(bumble bees, carpenter bees, solitary bees, etc.), which are unaffected by the mites,
may benefit from the absence of competition, and the presence of mites may be
slowing the northward spread of Africanized honeybees, also a non-native species.
And zebra mussels – one of the most costly invasives to date – have benefitted water
quality in the Great Lakes region (see Gallery).

1 David Pimentel, Lori Lach, Rodolfo Zuniga, and Doug Morrison. “Environmental and
Economic Costs of Nonindigenous Species in the United States.” BioScience, January 2000,
Vol. 50, p. 53-65. It represents one of the few attempts to date to provide comprehensive
cost estimates. (Hereafter referred to as Pimentel report.) Costs estimates in the study
included weeds, crop disease, rats, insect pests, non-native diseases of humans, zebra
mussels, and a variety of other species and categories. Domestic and feral cats and dogs
were included, and accounted for 4.9% and 0.1% of the total, respectively. Some have
criticized the report as inflated, or as failing to count benefits of other introduced species.
2 Each of these species is covered, in this order, in A Gallery of Invasive Non-native
Plants and Animals at the end of this report; see these entries for documentation of
economic impacts.

Major Laws and Executive Order
Because the problem of non-native species has continued to present itself as a
series of seemingly disconnected crises, legislation has also become a patchwork, as
each crisis was addressed. The laws addressing threats to agriculture (for centuries
a well-developed North American industry whose risks from non-native invasions
are relatively clear) tend to be more developed than laws protecting other industries,
or ecosystems. In consequence, agencies whose mission is to address those risks are
also better developed. Yet even there, responsibilities to protect agriculture from
non-natives which are established in some regions but not others, are diffuse, shared,
or even lacking. Moreover, the enormous volume of trade makes the burden on
understaffed federal inspection
systems so severe as to permit
What’s In A Name?only limited or cursory
Many names have been used to describeinspections, and force a strong
species that are able to survive and reproducereliance on self-reporting by
outside the habitats where they evolved or spreadimporters of living and non-
naturally. Among them are alien, exotic, injurious,living cargo.
introduced, invasive, nonindigenous, non-native,
and noxious. Alien tends to be applied to species
from other regions that are also harmful and likelyLaws protecting the
to proliferate wildly in their new habitat. Injurious,natural ecosystems on which
invasive, and noxious are generally usedsuch industries as tourism, the
synonymously and are not confined to specieselectric power industry, or city
outside of their normal range. These terms arewater supplies depend are far
applied to species that proliferate wildly, whetherless developed. In some
native (like white-tailed deer and barnacles) or non-important instances, such laws
native (like leafy spurge and brown tree snakes). Inscarcely exist at all. A state
the legal arena, these terms are found in variousagency which wishes to bring
laws and defined in various ways. This reportin a sport fish from another
generally uses the term non-native to emphasize thecontinent to benefit its anglers
geographic origin of these species, but the term
invasive is also used in deference to its increasingmay face few obstacles in
use among federal agencies. doing so, much less a burden
of proof to show that the
This paper focuses on those non-nativeaction will not harm other
species which have caused or seem likely to causeeconomic interests, natural
substantial economic harm. The authors recognizeresources, or ecosystems.
that many species (e.g., cattle, olives, wheat, tulips,
etc.) were introduced with either little knownNo comprehensive U.S.
adverse ecological impact, or with sufficient netlaw addresses imports of non-
benefits to make it likely that most people wouldnative species (see Federal
not consider them harmful.
Laws below for a summary of
current statutory provisions).
Some areas of interest lack
laws altogether. No obligation lies generally with those importing living organisms
(other than those already known to threaten agriculture) to show that the imported
species is safe. Some laws force the burden of proof in the other direction: an import
is deemed safe unless it is on a list of organisms known to be harmful. Special laws
to control imports of exotic aquarium fishes or pets, and the disposal of those pets
once owners tire of them, are lacking, or may be focused on some other issues (e.g.,

effects on populations of wild birds in the exporting country rather than in the United
Executive Order 13112. In response to rising concern, especially in southern
and western states plus Hawaii, President Clinton issued Executive Order 13112 on
Invasive Species (64 Fed. Reg. 6183, Feb. 8, 1999), revoking and replacing President3
Carter’s 1977 Executive Order 11987 on exotic species. The Executive Order seeks
to prevent the introduction of invasive species,4 provide for their control, and
minimize their impacts through better coordination of federal agency efforts under
a national invasive species management plan developed by an interagency National
Invasive Species Council. The Order directs all federal agencies to address invasive
species concerns as well as refrain from actions likely to increase invasive species
problems. The National Invasive Species Council, supported by an advisory
committee, was directed to develop recommendations for international cooperation,
promote a network to document and monitor invasive species impacts, and encourage
development of an information-sharing system on invasive species. (See National
Invasive Species Council below for more information.)
Preliminary Options for A Complex Problem
Non-native species introductions can be divided into those which were
intentional, or at least known by the person bringing in the living organisms, and
those whose arrival was probably not known to the persons involved. While there
may be disagreement over which species should be excluded among the many species
whose entry is sought, there appears to be no constituency for unintentional imports.
Rather, opposition results from the effects of regulations on trade or travel generally
that might arise from efforts to prevent introductions. Therefore research on which
pathways pose the greatest risks, and on the least intrusive mechanisms to reduce
those risks, could offer substantial benefits with reduced harm to trade and travel.
However, with the possible exception of controls on ballast water and some
agricultural pathways, little has been done systematically to identify or control
additional high risk pathways. Congress may wish to consider requiring studies to
(a) identify other high risk pathways; (b) identify (or create) suitable methods to
prevent further introductions via these pathways; and (c) investigate methods to
reduce inconvenience of control measures to travelers and shippers using those
pathways. Untreated wood used in pallets, packing material, crates, and barrels;
airline cargo holds; ship hulls, holds and ballast tanks; used tires, etc. are among
possible targets for broader risk assessment or controls.
In contrast, intentional introductions present a different set of problems.
Because many deliberate releases of non-native organisms have not been well-
planned and have not taken into account the potentially injurious nature of the exotic

3 For more information on the legal status of Executive Orders, see CRS Report 95-772 A,
Executive Orders and Proclamations.
4 Invasive species are defined in §1 of the Executive Order as “alien species whose
introduction does or is likely to cause economic or environmental harm or harm to human

species, nor compared the potential risks with expected gains, some organizations
have developed guidelines and codes of practice. The American Fisheries Society,5
the International Council for the Exploration of the Sea, the World Resources
Institute,6 and the Food and Agriculture Organization of the United Nations7 have
prepared such guidelines to assist regulatory bodies and other groups in determining
whether an introduction is justified, and then to advise them on what to do after an
introduction is approved. These guidelines complement the legislation described
later in this report by providing a conceptual framework for determining whether the
risk of introduction is acceptable, and then suggesting quarantine, monitoring, and/or
adaptive management if an introduction is approved. Components of these
guidelines have been incorporated in national legislation in the United States and
Rapid response to news of a recent introduction of an invasive species is also
an area being considered for improvement. In this respect, lessons might be learned
from the National Interagency Fire Center (NIFC), primarily under the management
of the Bureau of Land Management. Response to wildfires faces many of the same
problems of haste, technical needs, and interagency and intergovernmental
coordination. All federal land managing agencies participate in the NIFC, and a great
deal of the program focuses on work with tribal, state, and local governments to bring
many resources to bear on major fires. Somewhat similar problems are also faced at
the federal Center for Disease Control and Prevention in Atlanta. Either program
might provide models for congressional consideration.
Predicting an Invasion: Black and White?
Federal laws have tended to focus on exclusion, or “black lists,” i.e., on species
that have already been shown to be harmful (anything not on the list is allowed), in
contrast to a “white list” (anything not on the list is excluded). The black list can be
prepared in various ways, but is usually made up of species already shown to cause
serious damage to fisheries, endangered species, or (especially) agriculture.8 An
alternative approach would be to attempt to predict potential harm before a species’
arrival. The prediction would be based on known characteristics of a species, such
as how it reproduces, the number of seeds or offspring, etc.
A central dilemma, however, is the difficulty in making this prediction. What
characteristics of seed dispersal, nesting, food and host preferences, etc., are most
likely to lead to exuberant proliferation and result in economic and ecological harm?
Even more fundamentally, of the many millions of species on the planet, which ones
should be tested? For example, it seems logical that, all else being equal, plants

5 []
6 []
7 Devin M. Bartley, R.P. Subasinghe, and D. Coates, Framework for the Responsible Use
of Introduced Species, EIFAC/XIX/96/inf. 8. Report of the 19th Session, (Dublin, Ireland:
European Inland Fisheries Advisory Commission, 1996).
8 It should be noted that black lists do not readily address introductions by persons who are
unaware that they are bringing in non-native organisms.

producing many seeds will be more invasive than those producing few seeds. The
problem is that all else rarely is equal: a variety of factors affect “invasiveness.” The
abundant seed producer may require a special pollinating insect; the newly arrived
plant with few seeds may leave behind its major herbivores, etc. A host of other
factors may complicate prediction. No evidence to date has identified a suite of
features in plants or animals that seems to be a truly reliable predictor of
invasiveness, and thus many experts view all importations as suspect.
One observer argued that a somewhat reliable predictor is what he called
“propagule pressure.”9 In very simple terms, this means that those species that
“attempt” invasions (arrive in large numbers) most frequently and/or with the largest
number of arriving individuals are most likely to have some success at invading.
Scientists continue to model various factors which might contribute to invasiveness.
Nonetheless, many scientists will likely prefer the strictest possible exclusionary
policies, including white lists, because they lack confidence in these models.
In contrast, a number of industries depend in some respect on introductions of
non-native species. These industries include florists as well as the horticulture, pet,
and aquarium industries. They argue that a white list approach would exclude many
species that were unlikely to cause harm, or else would require inordinate economic
burdens on their industries to prove that a given imported species was safe. Further,
paperwork to prove that an imported species was indeed one that was on the white
list, could be burdensome as well. These groups strongly prefer a black list approach.
Whether a list is white or black, however, still implies that the importers
actually know they are importing living organisms. An effort to prevent
unintentional introductions would be compatible with any shade of list.

9 Mark Williamson, Biological Invasions (London: Chapman & Hall, 1996), Chapter 2,
p. 28-54.

Threat of Harmful Non-Native Species
A variety of abundant non-native species have had severe economic impacts on
U.S. industries and the natural environment. The increasing number of introductions
and greater estimates of their cost are causing pressure on Congress to develop new
responses to the problem. For example, according to a 1993 study by the Office of
Technology Assessment OTA), just 79 of over 4,500 non-native plants and animals10
in the United States caused over $97 billion in damage between 1906 and 1991. A
more recent study estimated current damage from all of the species examined at $12311
billion annually. Damage varies by species, and can span an enormous range of
effects, including power outages; loss of farmland property value; contamination of
grain; spread of disease; increased operating costs; loss of irrigation water; collapse
of buildings; competition with native plants; loss of sport, game, or endangered
species; ecosystem disturbance; etc.
Some non-native plants have been notorious for years for causing both
economic and ecological damage; kudzu, melaleuca, cordgrass, salt cedar, purple
loosestrife, spotted knapweed, and Russian thistle are just a few examples of
unwanted plants now causing ecological and economic harm in large areas of the
United States. Their damage includes lowering water tables, poisoning humans and
livestock, decreasing crop yields, and increasing pest control costs. A serious12
infestation can cause substantial losses in property values.
Non-native invertebrate pests are also well-known: gypsy moths, Japanese
beetles, Asian longhorned beetles, Asian tiger mosquitoes, fire ants, Africanized
honeybees, and zebra mussels are among the most well-known. Introduced
vertebrate pests (e.g., walking catfish, lake trout, cane toad, brown tree snakes, monk
parakeet, starlings, feral goats, bighorn sheep, nutria, rats, etc.) can also have serious
economic and ecological impacts. These effects can also include the introduction of13

various human parasites and diseases.
10 U.S. Congress. Office of Technology Assessment. Harmful Non-Indigenous Species in
the United States. OTA-F-565. Washington, DC: U.S. Government Printing Office,
September 1993, p. 3-5. (Hereafter referred to as “OTA Report.”)
11 Pimentel report. This study covered a broader array of species than the OTA report, and
extrapolated estimates from available sources. (See Pimentel report for precise
assumptions.) The arrival of more species since 1991 and a larger economy alone would be
expected to increase damage substantially.
12 A serious infestation of leafy spurge (Euphorbia esula) on an Oregon ranch caused a drop
in property value from about $125-$150 per acre to $22 per acre over 10 years. (Federal
Interagency Committee for the Management of Noxious and Exotic Weeds. Invasive Plants:
Changing the Landscape of America. Washington, DC, p. 27; hereafter referred to as the
“FICMNEW report.”)
13 While the transfer of human pathogens such as smallpox, syphilis, measles, AIDS, and
malaria from continent to continent has enormous human, ecological, and economic
consequences, human pathogens and parasites will not be covered in this report, though a
few disease vectors (species that can transmit diseases to other organisms, but are not
themselves pathogens) are mentioned.

In some of these cases (e.g., kudzu, melaleuca, gypsy moths, Africanized bees,
zebra mussels, and starlings), the source of the introduction is either known or
strongly suspected. Introducers of some species, such as kudzu, melaleuca, and
starlings, actually intended that their imports proliferate in the wild. Their purposes
ranged from the practical (kudzu for erosion control) to the quixotic (starlings for a
purported desire to bring all of the birds mentioned in Shakespeare’s works to the
United States). Whatever the motive, society itself was the loser in the importers’
Faustian bargains as the organisms proliferated to the detriment of the economy,
native fauna and flora, and ecosystems. Had they foreseen the damage these species
would later cause, governments at all levels would probably have worked to prevent
these introductions.
Introductions of non-native species may be intentional or unintentional. Some
intentional introductions produced benefits (or at least low levels of harm), as in the
case of the ring-necked pheasant, a game bird native to Asia. Unintentionally
introduced species may be present for years or decades before their presence is even
recognized, and the harm that they do, if any, is measured or observed.14 However,
catastrophic results can come from both accidental introductions (e.g., zebra
mussels), and intentional introductions (e.g., hogs to Hawaii).
A wide variety of intentional introductions have had effects which, even if
harmful to natural ecosystems or biodiversity, have produced economic benefits
sufficient to cause acceptance of collateral damage. These include such food sources
as cattle, wheat, honeybees, kiwi fruit, and soybeans, and such ornamentals as tulips,
chrysanthemums, and dawn redwoods, to name only a few. In each case the
introduction of these species was very much intentional and their propagation was
more or less controlled. The economic benefits conveyed by these species are vast,
and probably exceed the $123 billion figure cited above for the annual costs of non-
native species.15 U.S. agriculture would have a far different appearance if it were
limited to the several dozen food crops known to have been cultivated in North
America before 1492 rather than the hundreds of crops grown today. These non-
native crops and their benefits are not the focus of this report, but should not be
forgotten in discussions of those imported species which cause serious harm.
However, even in the case of non-native species conveying obvious benefits to
humans, the introductions of non-natives are not without ancillary dangers,
sometimes to the interests of those importing the target species: cattle can bring in
seeds and new diseases, tubers can bring in insect pests, and soil from roots or
hooves can harbor diseases for native plants. There may be damage to local
ecosystems as they are deliberately modified to accommodate new plants or animals;
in many cases (e.g., tulip cultivation or chicken ranches), society has accepted

14 Measurements of the number of non-native species that do no harm is exceedingly
difficult: by being innocuous, they escape study. Similarly, Kentucky blue grass (Poa
pratensis, which, despite its common name, may have been an early import from Europe)
now serves as important forage for native herbivores in much of the United States, and its
benefits are equally hard to measure.
15 No estimates of the benefits of desirable non-native species were found. A short
discussion of industries and interests benefitting directly from non-natives is given on p. 23.

conversion of land to support these species. On the other hand, controversies over
grazing rights for such non-natives as cattle and sheep show that acceptance is not
automatic. Examples of these attendant risks and problems will be considered below.
This paper will focus on species prone to (a) escaping human control or whose
potential for escape is unclear, or (b) harboring or transporting other undesirable
species. Predicting either of these risks is one of the most difficult problems in
addressing invasions by non-native species.
Numbers of Non-Native Species in the United States
If a new kind of tree grows in the forest, no one hears of it, at least not for a long
time. When new organisms are introduced to a new site, they must find conditions
adequate to their needs, depending on the biology of the species (e.g., food, rainfall,
temperature, or mates), and must avoid predators and diseases. As a result, scientists
agree, the great majority of biological introductions, whether caused by humans or
occurring naturally, tend to fail. Of those that succeed, a small fraction become
serious pests. A new species can exist in an area for decades without being noticed.
For that reason, the number of non-native species counted in an area (if such counts
are made) is likely to underestimate of the number of non-native species in the area.
So vast is this “bioinvasion” (as some have termed it), that only rough estimates
can be made of the numbers of non-native species now in North America, much less
the rest of the world. The 1993 OTA study cited above summarized information
known then on the number of non-native species in the United States. (See Table
1.) It divided the species into those of foreign origin, and those of U.S. origin that
had been introduced outside of their native ranges. As the OTA study noted, “These
numbers should be considered minimum estimates. Experts believe many more
[non-native species] are established in the country, but have not yet been detected.”
A more recent report estimated 30,000 non-native species in the United States.16

16 Pimentel report.

Table 1. Estimated Numbers of Non-Native Species
in the United States
Species with origins outside the United States
CategoryNumberPercent of total species in
United States by category
Plants >2000 unknown
Terrestrial vertebrates142~6%
Insects and arachnids>2000~2%
Mollusks (non-marine)91~4%
Plant pathogens239unknown
Species of U.S. origin introduced beyond their natural ranges
Plants unknown unknown
Terrestrial vertebrates512%
Insects and arachnidsunknownunknown
Mollusks (non-marine)unknownunknown
Plant pathogensunknownunknown
Source: U.S. Congress. Office of Technology Assessment. Harmful Non-Indigenous
Species in the United States. 1993. p. 92. Various original sources cited in report. Totals
and percentages shown here are likely to be underestimated: entire groups of organisms
(e.g., many categories of non-marine invertebrates) are not included; other studies show
higher numbers of non-native plants, etc. See text for discussion.
A Brief History of Introductions
The first human introduction of a non-native species into North America is lost
in antiquity. Nomads crossing the Bering Strait brought their dogs with them over
10,000 years ago. Polynesians landed in Hawaii bearing pigs, rats, and crop seeds
over 1500 years ago. Nearly a thousand years ago, Icelandic settlers in what is now
Greenland brought cattle, sheep, and goats with them (and perished with them,
possibly due to a reliance on European livestock unable to find fodder in an
increasingly harsh climate). Corn, native to Central America, was spread over much
of North and South America well before 1492. In the 17th Century, Puritan colonists

released domestic pigs into the New England forests to fend for themselves and
provide food for the colonists. By the 1840s the descendants of the Puritan’s pigs
were as common “as grains of sand on the sea-shore” in midwestern forests.17 The
colonists also brought smallpox, measles, brucellosis, and other undesirables, to the
severe detriment of native populations, both human and non-human. Some, like
dandelions and Norway maples, have been in this country for so long that their non-
native status is remembered largely by specialists.
According to the OTA report “[e]stimated numbers of [non-native species] in
the United States increased over the past 100 years for all groups of organisms OTA
examined.”18 Contributing factors include increases in the number of people
traveling, the speed and methods of travel, trade generally, improved ability and
speed in moving living plants and animals so that more of them survive the journey,
the increase in modes of transport for hitch-hiking organisms (such as ship ballast
water, pallet wood, and airplane wheel wells), the desire to have familiar sport and
game animals in new areas, trade in horticultural and garden plants, trade in pets and
aquarium animals, etc.
Geographic Origins of Non-Native Species
Plants and animals tend to survive best in a new site when that site is similar to
their original habitat. Formosan termites arriving in New Orleans are much more
likely to thrive than Formosan termites whose next stop is Anchorage, and a northern
European grass seed traveling inside a prize bull is much more likely to survive in the
Chicago area than the same species would in Miami. Thus, the plants and animals
of northern Europe, Korea, northern China, Japan, and New England are more likely
to be a threat to the stability of each other’s ecosystems, than any of them would be
to the fauna and flora of Miami or Singapore. Regions with similar climates and
soils around the world are tending toward increasing biological homogenization as
plant and animal species spread and the new arrivals thrive at the expense of natives.
This reverses the normal evolutionary pattern of ever-greater species divergence
between two geographically separated regions — from biodiversity to “biosimilarity”
— as the new arrivals create a homogenized flora and fauna in the two regions.19

17 C. Dickens, 1842, p. 165 in From Coastal Wilderness to Fruited Plain, by Gordon G.
Whitney. (Cambridge, England: Cambridge University Press, 1994.)
18 OTA Report, p. 91.
19 One author calls the phenomenon “evolution in reverse,” though this can be misleading,
since species themselves do not return to previous evolutionary forms. Rather ecosystems
become more similar, contrary to typically increasing divergence. See Christopher Bright,
Life Out of Bounds: Bioinvasion in a Borderless World. New York, NY: W.W. Norton &
Co, p. 17 (1998). (Hereafter referred to as “Bright.”)

Near neighbors20 are less
U.S. as Source of Non-Native Specieslikely to be a source of pests.
While the focus of this report is on speciesCanada, whose northern forests
that are not native the United States, this country isare contiguous with those of the
itself a source of species which threaten ecosystemsUnited States, is not likely to be
elsewhere. The grey squirrel of the eastern anda source of forest pests, since its
northern states was introduced to Britain, where itforests have no meaningful
has severely threatened populations of the Englishbiological barrier separating
red squirrel. In 1958, Pan Am Airways and a localthem from our own.
hotel introduced largemouth bass into scenic LakeConsequently, if a native
Atitlan in Guatemala. The introduction led, in theCanadian species could survive
next 25 years, to the crash of a sustainable crabin a U.S. forest, it is probably
fishery and of several native fish, contributed to the
near-elimination of the commercial harvest of reedsalready here. Similarly, desert
used in local handicrafts, and forced the extinctionplants of the southwest are
of a bird found nowhere else. Moreover, theprobably shared with Mexico,
harvest of the bass has since plummeted.and neither country’s native
desert fauna or flora poses
And even at the ends of the earth, human fecalmuch of a threat to the other.21
coliform bacteria contaminate McMurdo Sound, the
major U.S. scientific research base in Antarctica.Pathways of Invasion
In an area thought of as earth’s most nearly pristine
environment, the bacterium Clostridium
perfringens contaminates over 80% of sea urchinsTo some extent, pathways
near the undersea outfall of the untreated sewageof invasion between countries
from the base. The scientist who discovered thiscan be predicted. The arrival of
contamination plans to study the effect, if any, thiszebra mussels and their
sewage contamination is having on the plants andattendant damage to city water
animals of the Sound. Analysts have identified nosupplies and electric utilities in
laws designed expressly to prevent the spread andthe Great Lakes area focused
proliferation of U.S. species in other countries,much attention on the ballast
except in agricultural areas.water of cargo ships as a
pathway for biotic invasion.
Similarly, the propensity of
brown tree snakes to hide in the wheel wells of airplanes has done much to focus
attention on air stowaways. The recent arrival of Asian longhorned beetles may play
a similar role in focusing attention on pallet wood, packing crates, live plants, and
airport warehouses as pathways and centers of biotic invasion. In general, any arrival

20 “Near neighbors” must be construed biologically. For example, a spiderling dispersed by
wind might easily be blown from British Columbia to Montana. A freshwater clam or a
deep soil insect would scarcely ever be transported naturally from one to the other.
21 However, the statement does not apply to all ecosystems. For example, the higher
elevation forests of the Sierra Madre in Mexico have been separated for millennia by
hundreds of miles of desert from ecologically very similar forests of the Rockies. Pests,
both plant and animal, could evolve in comparative isolation in these two areas, and be
transported only recently with greater links of trade and traffic. Thus, the flora and fauna
of either disconnected area could pose a threat to the other while the more continuously
connected desert species are much less likely to do so. Moreover, non-native species may
have invaded one area successfully without yet being found in the other; intervening desert
could provide protection from invasion.

of living or untreated material (water, wood, soil, etc.) should not be overlooked as
a possible pathway for biotic invasion. A comprehensive review of possible
pathways, their risks, options for control, and research needs is, to the authors’
knowledge, currently lacking.
Within countries, certain paths for species invasions are quite predictable. In
the 19th Century, the railroads over which cattle were transported were a major path
for the establishment of new plants. In the 20th Century, the zebra mussel quickly
escaped the drainage of the Great Lakes (probably via the artificial connection to the
Illinois River), and began its invasion farther and farther south into the Mississippi
River drainage.
In addition to the accidental introduction of non-native species, introductions
may occur from species deliberately brought into the country. In some cases, the
importer does not intend for the imported plant or animal to escape to the wild, and
in other cases, the purpose of importation is to promote its spread into natural
habitats to achieve some desirable goal. In the first category are the imports of non-
native pets and plants. The importer is hardly ever interested in seeing the imported
organisms escape. But once the specimens are sold, control is lost, and purchasers
sometimes release unwanted non-native fish from aquaria or garden ponds, for
example, into local lakes or streams, often feeling they are doing a humane thing by
letting the fish go.22 A garden or greenhouse plant imported for horticulture may
scatter shoots or seeds far more widely than expected. Water hyacinths, for example,
were brought from South America in the late 19th Century as pool ornaments. The
plant now covers thousands of acres in the southern United States, plus parts of Cape
Cod and California, as well as parts of Africa and Asia. Moreover, the non-native
animal or plant may harbor microorganisms that pose a danger to other species, even
if the animal or plant itself does not survive in the wild.
People deliberately release organisms into the wild for a variety of purposes.
Several species of fish were deliberately released into the Colorado River for sport
anglers. (The continuing presence of these fish has been one complicating factor in
efforts to recover threatened and endangered species in and along the river, as well
as to manage the river more naturally.) Salt cedar (or tamarisk) was introduced from
Central Asia into the desert Southwest in the early 19th Century, in part to control
erosion along river banks. The tree now forms dense thickets on more than a million
acres of riparian habitat. The thickets have generally little value for most native

22 According to one author, “By far the most ecologically disruptive sector of the pet
industry is the aquarium trade... Of those exotic fish species established in the United States
that are completely foreign to the country, about 65 percent arrived through the aquarium
trade.” (Bright, p. 162-163.). In contrast, the introduction of snakeheads (an Asian fish)
began when they arrived alive to be sold in a New York City fish market. Two live fish
were purchased and taken to Maryland where the buyer eventually decided not to cook them
and so put them in an aquarium. When the fish got too big he released them into a nearby
pond. They bred and their presence was discovered over a year later. See Snakeheads,

animals, and the trees are estimated to absorb more water each year than all the cities
of southern California.23
Basic Methods of Pest Prevention and Control
The critical first line of defense against harmful non-native species is prevention
of introductions, since success in controlling these species, once established, has been
poor. Prevention is desirable from an ecological standpoint, and is usually
economically advantageous, as most established non-native species cannot be
eradicated, and controlling them to acceptable levels, when or if possible, is usually
Because many deliberate releases of non-native organisms have not been well-
planned and have not taken into account the potentially injurious nature of the exotic
species, nor compared the potential risks with expected gains, some organizations
have developed guidelines and codes of practice. The American Fisheries Society,24
the International Council for the Exploration of the Sea, the World Resources
Institute,25 and the Food and Agriculture Organization of the United Nations26 have
prepared such guidelines to assist regulatory bodies and other groups in determining
whether an introduction is justified, and then to advise them on what to do after an
introduction is approved. These guidelines complement legislation described later
in this report by providing a conceptual framework for determining whether the risk
of introduction is acceptable, and then suggesting quarantine, monitoring, and/or
adaptive management if an introduction is approved. Components of these
guidelines have been incorporated in national legislation in the United States and
Inspections and quarantines are key components of prevention by which the
entry of non-native species via specific pathways might be controlled. This approach
requires that species recognized as pests be listed and thus prohibited from entry.27
Quarantines operate basically on either of two premises: (1) invest in strict control
at points of entry (by which time, it could be too late to prevent entry) or (2) attempt
to control what arrives (i.e., try to act on the source or point of export or regulate the
pathway of import). Ballast water management for ocean vessels is a means of
“quarantine” whereby a major pathway of potential import for aquatic species is
managed. A quarantine may also be posted on an area where a non-native species
has been introduced, to prevent its further spread and promote its eradication.

23 Bright, p. 149.
24 [] on October 24,


25 [] on October 24, 2002.
26 Devin M. Bartley, R.P. Subasinghe, and D. Coates, Framework for the Responsible Use
of Introduced Species, EIFAC/XIX/96/inf. 8. Report of the 19th Session (Dublin, Ireland:
European Inland Fisheries Advisory Commission, 1996).
27 For an overview of plant quarantine procedures and guidelines, see Robert P. Kahn, Plant
Protection and Quarantine. Vol. 1 Biological Concepts (Boca Raton, FL: CRC Press, Inc.,

1989), 226 p.

Inspections and quarantines for agricultural pests are a major responsibility of the
Animal and Plant Health Inspection Service (APHIS) of the U.S. Department of
Agriculture (USDA). In addition, various states (particularly California, Arizona,
and Florida) and territories conduct their own inspection programs aimed at
agricultural pests. However, inspections and quarantines may not be effective for
many species, especially non-target “hitchhiking” species, species which enter via
uncontrolled or unrecognized pathways, and species that have invasive potential but
are not yet recognized as pests.
Public education also plays a critical role in preventing the introduction of
harmful non-native species. Campaigns have been relatively effective in educating
the public about the hazards of bringing non-native plant species home from
vacation, or releasing undesirable exotic pets or aquaria life into the wild.28
Agriculture extension offices and the mass media are two generally effective means
for distributing popular information to the public. In addition, the importance of
educating specific groups, such as dock workers and vessel crew members, about
controlling harmful non-native species could be emphasized, and might be integrated
when possible with regulatory measures.
If exclusion and quarantines fail to keep a non-native species out of an area, and
a species becomes established, the problem shifts to control of the pest, which
includes preventing its spread between local areas and beyond any established
perimeter. Control of harmful non-native species is divided into two related tasks:
eradication where possible, and reduction to manageable/tolerable levels29 where
eradication is not possible. No single method of control is likely to be a panacea.
Few control methods, if any, promise eradication under conditions where a species
is well-established, but several methods, especially when used in combination and
continuously, might reduce some target species’ populations to tolerable levels.30
Eradicating very small populations before they become established may be possible
and is more likely if many methods are used intensively and in combination,
including treating outlying populations as soon as they are discovered.
For introduced species, control methods include at least nine basic categories:
(1) baits and attractants; (2) traps; (3) fumigants, repellents, and barriers designed for
confined spaces; (4) herbicides and pesticides (conventional and biological); (5)
biological control; (6) bounties and commercial exploitation; (7) cultivation control;
(8) mechanical removal; and (9) site removal. To apply any of these basic strategies
of control, substantial knowledge of the target species’ behavior, biochemistry,
dietary preferences, diseases, or other aspects of its biology is essential. The degree
of species specificity of the selected approach can be a valuable asset in targeting
control efforts. A number of species (e.g., the brown tree snake and the

28 The extensive national public education program using “Smokey Bear” very effectively
communicated the role that private individuals could play in preventing forest fires;
Smokey’s success may offer a model for preventing invasions of non-native species.
29 Identification of what might constitute such a manageable/tolerable level is subjective,
value-laden, and open to interpretation, depending upon who is affected.
30 In the absence of eradication, control practices strive to be permanent, because residual
pest populations could otherwise reproduce and return to problem levels.

Mediterranean fruit fly) have been the focus of several of these strategies. In
addition, control program managers should be expected to solicit public input early
in the process of formulating and evaluating control alternatives and to answer
questions from the public about possible human health, economic, and other effects
from control programs. The pros and cons of these nine strategies, and some of the
information needed to apply them, are described below.31 Comparatively more
discussion is provided on biological control methods as they can sometimes involve
the introduction of additional non-native species.
Baits and Attractants. Baits and attractants may be used to draw
unsuspecting individuals of a target species toward a potential source of food or
mates (see the additional discussion below on pheromones under “herbicides and
pesticides (biological)”), where the target species can be counted, trapped, killed, or
studied. Difficulties with baits and attractants commonly include sustaining a long-
term monitoring effort and preventing harm to non-target species. Baits and
attractants seem most promising when the area needing protection is well-defined
with clear boundaries and has a significant density of the target species.
Traps. Trap use is limited primarily by cost, time required to service traps, and
inability of traps to control target species over large areas. Various trap designs are
available, and most are used in combination with some type of bait. For confined
areas such as cargo holds, buildings, etc., traps may be relatively successful. On the
other hand, traps have obvious drawbacks in open situations with either abundant
alternative food or very low target species densities. Traps are comparatively safe
to use, although they require some care when trapped individuals are killed and
removed. Sticky traps have been used on rodents and brown tree snakes. Chinese
mitten crabs have been trapped at irrigation screens during their downstream
migration to spawn in saltwater.
Fumigants, Repellents, and Barriers Designed for Confined Spaces.
Lethal substances can be used to target pests in confined areas or to prevent them
from crossing a geographic bottleneck. These methods can be used either to create
pest-free “islands” in a zone of infestation or to prevent invasive species from leaving
an infested area via boxes, cargo holds, etc. Some species are known to avoid certain
substances, such as tear gas or gasoline. Obviously, these substances can be used
only to a limited extent in areas where there is infrequent human access, rather than
in area-wide application. Fumigants can also be used to kill or exclude pests from
confined areas, such as cargo containers. For example, the Environmental Protection
Agency has approved methyl bromide32 as a fumigant for the brown tree snake. Light
is also known to repel some nocturnal animals. Submerged surfaces have been
electrified at water and power facilities to discourage the settling of zebra mussel
larvae and on ship hulls to inhibit barnacle settlement. Physical barriers can be used
to prevent range extensions and access to new habitats, such as the electrical barrier

31 The discussion below draws heavily on U.S. Dept. of the Interior, The Brown Tree Snake,
Boiga irregularis, A Threat to Pacific Islands, Biological Report 88(31), (Washington, DC:
Fish and Wildlife Service, September 1988), p. 18-20.
32 For more information, see CRS Report 98-590 STM, Methyl Bromide and Stratospheric
Ozone Depletion Policy Issues.

being constructed by the Army Corps of Engineers in the Chicago Sanitary and Ship
Canal to prevent or reduce the dispersal of invasive aquatic species between the Great
Lakes-Saint Lawrence drainage and the Mississippi River drainage. Screens are used
to prevent the movement of aquatic plant fragments within waterways. However,
care is required to ensure that barriers do not impede the migratory behavior or
natural dispersal of native species.
Herbicides and Pesticides. These chemical control agents can be
subdivided into those derived from manufactured (conventional) or natural
(biological) sources.
Conventional. Where chemical control is an option, herbicides and pesticides
affecting or controlling only one or a group of related species are strongly preferable
since broadly toxic substances risk substantial harm to non-target species. For
example, TFM (3-trifluoromethyl-4- nitrophenol) is very specific in its toxicity to the
larval stage of lamprey. Similarly, a variety of aquatic herbicides can be used
specifically for the control of Hydrilla and water hyacinth. However, even if
pesticides are highly specific, safety precautions often suggest the use of chemical
control in conjunction with baits, thereby further reducing risks to pets, children, and
other non-target organisms.
Biological. Biological herbicides and pesticides (also known as biopesticides)
are derived from natural materials, such as animals, plants, bacteria, and certain
minerals. At the end of 2001, there were approximately 195 registered biopesticide
active ingredients and 780 products.33 Biopesticides can be divided into three major
classes: (1) biochemical pesticides are naturally occurring substances (e.g.,
pheromones) that control pests by non-toxic mechanisms (e.g., interfering with
mating);34 (2) microbial pesticides contain a microorganism (e.g., a bacterium,
fungus, virus, or protozoan) as the active ingredient, such as various types of the
bacterium Bacillus thuringiensis (Bt) used to control certain insects harmful to
cabbages, potatoes, and other crops;35 and (3) plant-incorporated protectants are
pesticides that plants produce from genetic material that has been added to the plant,
such as when the gene for the Bt pesticidal protein is introduced into a plant’s own
genetic material causing the plant to manufacture the substance that destroys pests.36
Although biopesticides tend to pose fewer risks than conventional pesticides (they

33 [] on October 24,


34 In some species (particularly insects), chemicals known as “sex pheromones” are given
off that allow males and females to find each other. Sex pheromones work even when target
species densities are low, and they are highly species-specific. For example, “Disparlure”
(the commercially synthesized sex pheromone of the female gypsy moth) is used to trap
male gypsy moths. Because it is sometimes difficult to determine whether a natural
pesticide controls a pest by non-toxic means, EPA has established a committee to determine
whether a pesticide meets the criteria for consideration as a biochemical pesticide.
35 Public concern has arisen over the use of Bt in some situations (e.g., for controlling Asian
gypsy moths) because of possible adverse health effects that may occur in people with
compromised immune systems.
36 Both the protein and its genetic material are regulated by EPA; the plant itself is not

tend to be less toxic, usually are effective in very small quantities, often decompose
quickly, and generally affect only the target pest and closely related organisms), users
need to know a great deal about managing pests to employ them effectively.
Biological Control. A biological control organism competes with, preys on,
parasitizes, or causes disease in a targeted pest species. Ideally, biological control37
agents attack the target species and no others. Considerable knowledge of both the
target species’ and the control organism’s basic biology and ecology is necessary to
select a suitable control. Screening requirements vary for selecting biological control
agents, with very stringent requirements for some uses, while requirements for other
uses may be nonexistent. Together, individual state laws and APHIS (through 7 CFR

371) regulate the introduction of biological control organisms, and the USDA,

through the Agricultural Research Service, administers a Biological Control
Documentation Program.
A particular concern with biological control organisms is that they might
commence feeding on non-target species once target species are sparse or eradicated.
An example of this problem is mongoose introductions. In the 1600s, mongooses
were introduced in Puerto Rico to eradicate rats, which they did with great success.
Unfortunately, mongooses proliferated and began to eat a variety of birds and other
native animals. Similarly, the house sparrow (Passer domesticus, or English
sparrow) was brought from Europe to control the canker worm. This non-native bird
now crowds out native birds and damages crops. In recognition of these problems,
vertebrate animals with broad feeding habits are seldom, if ever, used today as
biological control agents.
Production and release of large numbers of sterilized males has been particularly
successful in controlling various insect pests (e.g., medflies, screwworm flies,
Cochliomyia hominivorax) and sea lamprey. Competitive mating by sterilized males
results in lower reproductive rates for the invasive species population, reducing its
abundance and potentially controlling population spread.
Using a disease or selective parasite may be an attractive option in some
circumstances, but again there is a risk that the disease or parasite will attack non-
target species. Fieldwork in a target species’ native habitat is usually necessary to
identify diseases or parasites to which the target species may be susceptible.
Although the requisite research might be expensive, using biological control agents
holds hope for long-term control. The alligator weed flea beetle (Agasicles
hygrophila) for control of alligator weed (Alternanthera philoxeroides) and the
current program using several beetles (Galerucella pusilla, G. calmariensis, and
Hylobius transversovitattus) to control purple loosestrife are success stories for
biological control of plants. The brown tree snake of Guam could be a possible
candidate for biological control, since there is only one snake native to Guam and its
habitat is quite different from the brown tree snake’s. Thus, the chance of an
introduced parasite or disease affecting the native snake species is minimal.

37 The USDA requires proof of host-specificity before supporting an insect introduction for
non-native plant control.

Natural biological control can also occur through adaptive ecosystem response
by native species to invasive species. An example is the indigenous weevil,
Euhrychiopsis lecontei, which is a specialist feeder on northern water milfoil
(Myriophyllum sibiricum). Once this weevil is exposed to the non-native Eurasian
water milfoil (M. spicatum), it appears to change its feeding habits to preferentially
feed upon the Eurasian variety. In Oregon, the native defoliating butterfly, Vanessa
cardui, feeds on introduced thistles, Cirsium arvense and C. vulgare.
Other forms for biological control may involve planting competitive vegetation
and managing livestock grazing. For example, grazing by sheep and goats can be an
effective management tool for controlling leafy spurge.
Bounties and Commercial Exploitation. Under a bounty system,
someone is paid to catch and kill the target species. High bounties may have to be
paid to encourage sufficient control that results in a substantial effect on the target
species’ population. The problem, however, is that paying bounties can create a
market incentive — a particular risk when a population dwindles to very low levels
and prices go up or bounties are increased. In addition, these methods may have
incidental adverse ecological consequences for native species arising from increased
human traffic and collecting methods. In August 1999, the California Department
of Fish and Game decided against permitting the commercial harvest of non-native
Chinese mitten crabs, concluding that such harvest would not contribute to
controlling this species and might encourage further introductions.
Cultivation Control. Use of such measures as timing of fertilizer
applications, adjustment of planting dates, and crop rotation can be valuable
management and control tools for invasive weeds. Some cultivation control
methods, while minimal in cost and equipment, may require an additional
commitment of labor and are unlikely to be effective unless combined with other
control methods.
Mechanical Removal. Mechanical controls may be used to collect and
remove large volumes of invasive non-native species, particularly plants. Mechanical
harvesters may be used in the management of non-native aquatic vegetation, such as
Hydrilla and water hyacinth, but are ineffective for control of these species on large
bodies of water. Mechanical controls are also used to prevent the further spreading
of established non-native species, and include methods such as cleaning of equipment
(e.g., during highway construction) and using certified weed-free seed and feed (e.g.,
weed seeds have been mechanically excluded or removed). Mechanical control of
terrestrial plants includes such basic procedures as hand-pulling and mowing. Some
of these methods may require expensive specialized equipment or substantial
commitment of labor to be effective.
Site Removal. The recently introduced Asian longhorned beetle (still perhaps
at low enough levels to have some slight chance of being eradicated) is currently
being controlled to some degree by removing all trees on which the pests might feed
in neighborhoods where they have been found. Site removal has also been used in
California to eradicate Hydrilla by draining small ponds and filling their depressions
with earth. Such a drastic strategy would be unworkable if a pest becomes widely

Unusually Susceptible Habitats
Harmful non-native species occur throughout the United States, but some
ecosystems are more susceptible to invasion than others. Mild climate, geographic
isolation, disturbance of the natural landscape,38 and a high rate of exposure to non-
native species are all factors which can make a habitat particularly susceptible to
invasion. Islands and other long-isolated areas with unique plants and animals are
also known to be particularly susceptible to invasive species.
Hawaii and Florida, for example, each have many threatened and endangered
species and, not coincidentally, a plethora of harmful non-natives. Both states were
long isolated biologically and have large numbers of native species found nowhere
else. The mild climates of Florida and Hawaii make it easier for the rich flora and
fauna from the rest of the tropical and semitropical regions to survive, and also make
the states attractive to businesses that import and maintain or even breed non-native
animals and plants, such as tropical fishes and ornamental plants. In Florida, the
number of non-natives seemed overwhelming to a local reporter:
In southern Florida, especially, untrammeled whims of humans have introduced
so many species of non-farm animals (mainly as “pets”) that the native fauna is
greatly diluted. Running wild in Dade and Broward Counties have been
piranhas, walking catfish, blue tilapia (“introduced from Africa in 1961 by
officials of the Game and Freshwater Fish Commission”), electric eels, little
barbed Amazonian catfish that swim up [human] urinary tracts, and other fish
(“23 exotic fish now breeding in the wild”), Cuban anoles, iguanas, Asian water
monitors, caimans, boa constrictors, pythons, mambas (“people want the newest
animals as pets”), red-whiskered bulbuls, monk parakeets, howler monkeys,
gibbons, green African savannah monkeys, crab-eating macaques, and a herd of39

300 buffalo.

Both Hawaii and Florida are major travel destinations and transportation hubs, so
they are more likely to be subjected to inadvertent introductions. In both states, large
areas have been cleared of native plants. It is often easier for non-native species to
establish themselves in such disturbed habitats — in fact, many invasive species are
weeds that have evolved to exploit such land and then “hitchhike” to freshly
disturbed areas.
Another factor putting some environments at risk is the sheer number of
opportunities for new introductions. Seaports, in which ships have exchanged ballast

38 Some writers argue that evidence is lacking on how disturbance affects susceptibility to
invasions. But scientists generally accept the idea that severe depletion of an ecosystem’s
flora and fauna (e.g., through fire, storm, volcanic eruption, etc.) does offer significant
opportunities for newly arrived species, since the new arrivals face reduced competition in
disturbed habitat.
39 W. Belleville. “Critter patrol,” Florida (a news magazine of the Orlando Sentinel Star),
29 May 1994: 8-12, 15. Some of this paragraph may reflect the reporter’s view of the subject
more than a strict interpretation of fact. For example, not all of the species mentioned
actually reproduce in south Florida. In focusing only on exotic pets however, the paragraph
understates Florida’s problem.

water daily for decades or even centuries are at severe risk of invasions. Even if only
a tiny proportion of newly arriving non-native species survive in the new habitat of
San Francisco Bay, Chesapeake Bay, or Boston Harbor, the actual number of
successful, invasive species may be very large. The areas around airports, with
increasing volumes of international traffic and tourism, are also at risk. In addition,
the greater the similarity of the point of origin, the more likely the invasion is to be
successful. For example, biotic invasion of the Hawaiian islands is more likely to
come from a plane originating in Guam than one originating in Anchorage.
Available Estimates of Costs and Impacts
It is difficult to quantify the damage due to invasive species. One study by
Pimentel and his colleagues put annual costs and damage due to non-native species
at $123 billion per year.40 The study included no information about the overall costs
of excluding non-natives. The assumptions used in the study to make these estimates
may be questioned as over- or understating the costs; probably no two scientists or
economists would make the same assumptions to derive such an estimate. As one
of the first attempts to make a broad estimate over a very large range of species, the
figure of $123 billion should be construed an informed estimate, and the interested
reader should examine the report itself to assess the validity of the assumptions used
to derive the figures.
The handful of species highlighted in this report alone cause annual losses over
$3.5 billion, and two (Formosan termite and Asian river clam) are responsible for $1
billion each in control costs, diminished property values, and other damage. Even
if new imports of non-natives were completely halted (a near impossibility), the costs
of controlling established non-native species would continue.
The value and the cost of prevention are difficult to assess. In the absence of
any other information, since the first several thousand harmful non-native species
(i.e., those for which any numbers could be gathered) collectively were estimated to
cause about $123 billion annually in costs and damage, it seems reasonable to assume
that the next several thousand to arrive and become established could cause
comparable economic damage. Damage could include the same types of damage
already known to affect economies and ecosystems through power outages; changes
in flood regimes; increased erosion; loss of farmland property value; contamination
of grain; spread of disease; increased operating costs; inefficient irrigation; higher
risk of fire; collapse of buildings; loss of sport, game, or endangered species;
ecosystem disturbance; etc.. There could also be effects on industries or ecosystems
that have not yet been markedly harmed by non-natives (e.g., the threat to fall tourism
and the maple syrup industry in New England from Asian longhorned beetles, which
attack and kill a variety of tree species, but are particularly fond of maple trees and
their relatives).
Targeting each newly arriving non-native species individually seems very likely
to be more costly than targeting pathways or groups of species. A focus on high-risk
pathways could be more cost-effective over the long term, but a pathways approach

40 Pimentel report, p. 1.

itself has costs, as evinced by debate over the arrival of the Asian longhorned beetle.
In an effort to stop or slow the entry of this widespread Asian species, controls were
placed on its suspected major pathway — raw wood packing material of imports
from China (rather than from all the Asian countries in which this species is
common) and, for a time, the controls threatened a trade war with China. It also
escalated federal government attention to the problem of non-natives to the highest
levels of government. (See Asian Longhorned Beetle, below.)
Another cost of biological invasion is restoration of disturbed habitat, if it is
undertaken at all. Damage due to an invasive species tends to rise as the species
becomes established. Education of the public (which may stop the transport of many
species before it even starts) can be relatively inexpensive on a per species basis. At
each subsequent stage — transport, release, establishment, and spread — the cost of
eradicating the non-native typically increases. And once the species is established
over a wide area, eradication could be virtually impossible for any reasonably
foreseeable sum. If a non-native becomes established and some local (and
necessarily continuing) control occurs, restoration of the damaged habitat might be
attempted, insofar as possible. Restoration could involve recruiting small armies of
volunteers to pull non-native plants, hiring sharpshooters or trappers to kill or capture
animals, transporting animals to native habitat, dredging streams and lakes, poisoning
lakes, etc. Many restoration efforts could involve not only major costs but also
substantial political controversy.41
The controversy illustrates the dilemma for policymakers. Specifically, the high
cost to many industries (even seemingly unlikely ones, such as imported computer
parts, steel, or other products with no obvious connection to living organisms), to
economic interests, and to ecosystems from unwanted species is balanced against the
costs of protective measures imposed on commerce in general. It will also have to
be balanced against the needs of domestic industries (horticulture, agriculture, pet
trade, etc.) that depend directly on importing non-natives.

41 The manager of one national wildlife refuge (in Hawaii) told one of the CRS authors that
no control efforts at all would be attempted at that time in one distant area of the refuge that
was overrun with non-native species, since only very substantial budget and time
commitments would produce results, and any effort short of that would be a waste of money.
Failing that, control efforts were instead directed to other areas with greater chances of
success within available budgets. Restoration costs at that refuge might therefore be
considered either zero — or completely insurmountable.

Industries That Benefit from Non-native Species
While the ecological damage from some non-native species can be great, only
a small percentage of arrivals have proved to be economically harmful, and many are
beneficial.42 (For many species, the economic impacts are simply unknown.) Some
industries rely heavily on non-natives. For example, nearly all food plants and
animals in the United States are not native to the areas where they are now grown.
Besides agriculture, industries relying significantly on non-native species include the
nursery, aquaculture, and pet industries.
Most woody invasive plants in the United States were originally introduced by
the landscape industry.43 The giant hogweed, whose toxic sap can cause severe
scarring, was introduced as an ornamental but escaped cultivation and is now widely
listed as a noxious weed.44 Similarly, water hyacinths were introduced, apparently
as an ornamental for garden ponds. (See Gallery, below.) As a result of this and
similar escapes, the nursery industry has been subjected to increasing criticism.
States are increasing their regulation of potentially invasive species.45 Some of those
species are economically important to the nursery industry. Some industry groups
have been working to develop voluntary controls to lessen the risk of inadvertent
introduction of invasive plants.
Production from private aquaculture nearly tripled from 1985 to 1999 and was
worth more than $987 million in 1999.46 Many cultured species are not native.
There is concern about the escape and establishment of cultivated species that may
be harmful to native ones. Examples include the threat of Atlantic salmon in the
Pacific Northwest; and the inadvertent introduction of diseases, such as dermo and
MSX in oysters; or of other pest species. Concerns are similar for the aquarium and
exotic pet trades, which rely heavily on tropical species. The United States is the
world’s leading importer of reptiles, for example, and though the chief concern has
been for potential effects on source countries (e.g., iguanas from Central America),
there are concerns regarding possible escapes, especially in southern states.47 A
number of the species (some described in the Gallery below) were thought or known

42 Only a few commercial foods now grown in the U.S. are apparently native to this country.
Known examples include sunflowers, Jerusalem artichokes, pecans, black walnuts, some
wild cherries, strawberries, blueberries, and cranberries. Other familiar foods of the new
world (e.g., corn, potatoes, chilies, and tomatoes) either were not grown in this country in
1492, or were non-natives brought in earlier by Native Americans. For some foods, the
native range is still debated.
43 S.H. Reichard and C.W. Hamilton, “Predicting Invasions of Woody Plants Introduced
into North America,” Conservation Biology, vol. 11 (1997):193-203.
44 Mary Robson, “The Perils of Giant Hogweed,”
[], 5 July 1998.
45 FICMNEW report, p. 86-91.
46 U.S. Joint Subcommittee on Aquaculture, “U.S. Private Aquaculture Production for

1985-1999,” October 2001. []

47 Data from Traffic International [],
established to assist in the implementation of the Convention on International Trade in
Endangered Species.

to have entered the United States as pets, or in association with pets: caulerpa,
hydrilla, apple snails, goldfish, walking catfish, budgerigars, ring-necked doves, and
common pigeons.48
Harm to the Natural Environment: Diffuse Responsibilities
Responsibilities for native flora and fauna and the ecosystems in which they live
are scattered — the wards of many or of none. Generalized effects on ecosystems
from very large to very small (e.g., the Great Lakes, suburban trees, Texas lawns) are
not the specific responsibility of one federal agency. With so many pathways for the
entry of non-natives, so many possible entering species, and so many possible and
nearly unknowable injured species, the natural ecosystem as a whole has no specific
guardian. This scattered responsibility is a result of the evolving legal history of
species protection,49 agriculture, and import regulation.
U.S. law concerning native wild plants and animals is not a comprehensive body
at the federal level. Under our system, inherited from English legal tradition, and
stated very simply, the government regulates the “take” of native wild animals
generally, and landowners control the native (and other) plants growing on their
lands. A wild deer walking across a pasture does not “belong” to the landowner but
is rather the government’s to regulate; the bush it eats belongs to the landowner.
Thus, colonial governments regulated native wild animals and, after the U.S.
Constitution was ratified, the states retained the rights they previously had as colonies
to control the wildlife within their boundaries.
Aside from special rules for lands owned by the federal government, federal
native wildlife law can be thought of as a series of exceptions to the general concept
that states regulate wild animals, and landowners manage (or don’t manage) wild
plants. Some of the major exceptions to that generalization include federal laws
regulating the taking of migratory birds (pursuant to treaties), marine mammals, and
endangered species. The great majority of native wild plant and animal species do
not fall into any of these categories and therefore are not direct federal
responsibilities under current law.
Native wild flora and fauna are frequently protected as a consequence of
protecting something else — agriculture and endangered species, for example.
Where there have been specific injuries to other industries or interests (utility intakes,
for example). the pathway by which the harmful species arrived may be regulated to
prevent other non-natives arriving via that pathway. Natural ecosystems, as result of
the threats to other interests, may benefit from an incidental reduced risk of harm
arriving by a pathway that is controlled.

48 For an overview of the risks of both plants and animals introduced from the aquarium
trade, see [].
49 For a general discussion of early development of federal wildlife law, see The Evolution
of National Wildlife Law, 3rd ed., by Michael J. Bean and Melanie J. Rowland (Westport,
CT: Praeger Publishers. 1997), p. 7-14.

Federal Laws
Federal law concerning non-native species is scattered. No laws focus on the
broad problems of non-native species, their interception, prevention, and control
across a variety of industries and habitats. The body of law addressing non-native
species and agriculture appears better-developed than laws relating to other sectors
of the economy or the nation’s natural resources. Some laws, though they do not
directly address non-native species control or prevention, have effects that may limit
such introductions. Below is a brief digest of existing laws, presented in
chronological order of enactment, which affect non-native species introduction,
prevention, and control. However, control of non-native species is not the major
purpose of the law in some cases included below. In addition to federal laws, a
number of states have laws restricting transport or possession of non-native species.
State laws are not described in this report. Also omitted are the handful of federal
laws referring to single species.
Lacey Act
Originally enacted in 1900, the Lacey Act (16 U.S.C. 3371-3378, 18 U.S.C. 42)
makes it illegal to import, export, sell, receive, acquire, or purchase fish, wildlife, or
plants50 taken, possessed, transported, or sold in violation of U.S. or tribal law. In
addition, this Act makes it unlawful to engage in interstate or foreign commerce
involving any fish, wildlife, or plant material taken, possessed, transported or sold
in violation of state or foreign law. Specific provisions authorize the federal
government to prescribe requirements and issue permits for importing wild animals
under humane and healthful conditions.51
One portion of the Act (18 U.S.C. 42) appears to give the Secretary of the
Interior and the Secretary of the Treasury considerable power to exclude three major
categories of non-native animals: vertebrates, crustaceans, and mollusks. Moreover,
grounds for exclusion were expanded beyond the traditional harm to agriculture,
horticulture, and forestry interests to include harm to “wildlife and wildlife
resources.” The inclusion of the latter could mean that nearly any non-native
member of these groups could be considered for exclusion, since most and perhaps
all ecologists would hold that the proliferation of any non-native species in an
ecosystem risks harm to its wildlife resources. The reach of the law is somewhat
unclear, however. Is the Secretary of the Interior to prepare a “white list” or a “black
list”? In the 1970s, the Interior Department interpreted the provision as permitting

50 Plants are commonly covered under somewhat different provisions than animals are. To
be covered under the Lacey Act, plants must be “indigenous to any state” and either
protected under the Convention on International Trade in Endangered Species or under a
state law protecting species threatened with extinction. Thus, a state like Hawaii apparently
could not use the Lacey Act to help enforce that state’s laws designed to keep out common
native (mainland) plants. On the other hand, the Act might help the same state exclude
animal pests from other states, whether native to the state of origin or not.
51 The term “wildlife” can have various meanings in federal and state laws, including game
species; game species except fish; mammals (rather than birds); or the entire animal

a white list, and attempted to develop regulations accordingly. Public protest, chiefly
from the pet industry but also others, stopped the process.52 Current regulations,
which adopt a black list approach and name only a small number of species to be
excluded, are found at 50 CFR Part 16.
Animal Damage Control Act
The Animal Damage Control Act of 1931, as amended, (7 U.S.C. 426 et seq.)
is the primary statute under which APHIS operates its Wildlife Services (WS)
program (known until 1997 as the Animal Damage Control program). The Act gives
APHIS wide authority to control wildlife damage on federal, state, or private land.
WS is involved in protecting: (1) field crops, vegetables, fruits, nuts, horticultural
crops, and commercial forests; (2) freshwater aquaculture ponds and marine species
cultivation areas; (3) livestock on public and private rangeland and in feedlots; (4)
public and private buildings and facilities, such as houses, commercial properties,
swimming pools, golf courses, reservoirs, levees, and landfills; (5) civilian and
military aircraft (against collisions with birds); and (6) public health (against wildlife-
borne diseases such as rabies, Lyme disease, West Nile virus, and plague). WS
control methods include providing advice to individuals and to municipal, state or
federal agencies on a wide variety of preventive, non-lethal control methods. Control
of predatory animals, native or non-native, is largely carried out by lethal means,
including hunting, trapping, and poisoning.
WS also has cooperative agreements with the Fish and Wildlife Service (FWS),
the National Park Service, the Bureau of Land Management, the Forest Service, and
state natural resource agencies to help protect natural resources, including wildlife
and threatened or endangered species, from loss of life, habitat, or food supply due
to the activities of other species. Under the authority of the Act, as broadened by the
Agricultural Appropriations Act of 2001 (P.L. 106-387), APHIS addresses damage
problems caused by such non-native species as nutria, European starlings, and monk
parakeets. Also in 1991, Congress passed P.L. 102-237, which (among other things)
amended the Animal Damage Control Act specifically to add the brown tree snake
to the list of animals that WS is charged to monitor and control.
Federal Seed Act
The Federal Seed Act of 1939, as amended (7 U.S.C. 1551 et seq.), requires
accurate labeling and purity standards for seeds in commerce. Among other things,
the Act prohibits importing and moving adulterated or misbranded seeds, and
imposes labeling requirements. The Act also authorizes enforcement activities and
rulemaking functions. In addition, this Act regulates interstate and foreign commerce
in seeds, and addresses “noxious weed seeds” that may be present in agricultural

52 For a brief history of these actions, see Michael J. Bean and Melanie J. Rowland. The
Evolution of National Wildlife Law, 3rd ed. (Westport, CT: Praeger Publishers, 1997), p.
53-55. These authors argue that the legislative history of the Act is unclear on the question
of species-by-species lists. If white lists were permitted, the statute could be a powerful
check on importing and transporting non-native animals in the three major taxonomic groups
it covers.

(e.g., lawn, pasture) or vegetable seed. APHIS administers the foreign commerce
provision of this Act; the Agricultural Marketing Service administers the interstate
commerce provisions. The law works in conjunction with Plant Protection Act to
authorize APHIS to regulate only imports of agricultural seed that may contain
noxious weed seeds.
National Environmental Policy Act of 1970 (NEPA)
NEPA (P.L. 91-190, as amended; 42 U.S.C. 4321, et seq.) requires, among other
things, that federal agencies consider and consult with the public about the
environmental effects of their actions. The primary mechanism to achieve this end
is the preparation of environmental impact statements (EISs) for major federal
actions affecting the environment. Agencies are expected not only to prepare EISs,
but also to comment on the EISs prepared by other agencies.53
This law could apply to some introductions of non-native species. If a federal
action might affect the risk of introducing or spreading non-native species, thereby
having a significant impact on the natural and human environments, the associated
EIS would have to address this possibility. The limitations of NEPA vis-a-vis its
application to non-native species include:
!limited applicability to actions without a federal connection;
!inapplicability to completed federal actions, although these actions
may have effects that continue into the present;
!limited utility if the possibility of introducing non-native species is
not foreseen; and
!the inability of scientists to provide agency administrators with the
information necessary to assess the risks or consequences associated
with introducing most non-native species.
If NEPA is invoked, the opportunity for significant analysis of a proposed action via
an EIS is great. The resulting analysis may cause modification or abandonment of
some actions or alternatives, if serious objections are raised. However, because
NEPA is essentially procedural, it does not, by itself, prevent an activity, even if the
risk of unfavorable environmental outcomes is high. Nonetheless, failure to consider
the issue of non-native introductions could be grounds for requiring an agency to
amend its EIS, thereby delaying the introduction and risk while the revision is

53 For an overview of NEPA, see CRS Report 97-49 ENR, Summaries of Environmental
Laws Administered by the Environmental Protection Agency, p. 109-113. While the focus
is on the responsibilities of that agency, the fundamentals of the Act are also explained.

Endangered Species Act (ESA)
The ESA54 (P.L. 93-205, as amended; 16 U.S.C. 1531-1543) focuses its
attention on species that are rare, not those that are common to the point of being
weeds or pests. However, the strong protections offered under the ESA for rare
species may provide a vehicle for regulating non-native species. For example, in the
Pacific Northwest, the threat to resident salmon species protected under ESA is a
major argument being used against the introduction or expansion of aquaculture for
Atlantic salmon. Similarly, introduction of mountain goats in an area where they are
not native would be more likely to be questioned if there are local endangered or
threatened plants likely to be harmed by the goats.
ESA could provide protection in two ways. First, if the introduction were to be
carried out by a federal agency or require licensing, financial support, permits, etc.,
from a federal agency, the agency involved would have to consult with FWS or
National Marine Fisheries Service (NMFS) to determine whether the introduction (or
action leading to introduction) would tend to jeopardize the continued existence of
the listed species or adversely modify its critical habitat. If so, the introduction
would usually be prevented or modified to reduce the risk. Second, if the action had
no federal nexus, but its effects could result in taking (as defined in the Act) a listed
species, the party carrying out the action would have to obtain an incidental take
permit from FWS or NMFS.
Questions of knowledge, intent, and causality affect whether violations under
the ESA have occurred and whether penalties may be applied. Therefore, as a
practical matter, ESA is an unlikely alternative for penalizing the introduction of
non-native species because the persons responsible for introducing many non-native
species may never be known and introduction is often inadvertent. For example, it
is not known who introduced zebra mussels, and it is likely that their probable
introduction via ballast water was unintentional. In addition, introductions may go
unnoticed for a long time, compounding the difficulty in determining responsibility.
For example, the introductions of the brown tree snake on Guam went unnoticed for
years after their arrival, though the brown tree snake is strongly suspected of being
directly responsible for the extinction of several species on Guam. Consequently,
enforcement actions under ESA in the usual sense are unlikely.
However, the policies of the ESA and the duty of federal agencies to ensure that
federal actions will not jeopardize species listed under the Act may result in changes
in certain practices and the tightening of regulation of potential pathways, e.g.,
greater regulation of ballast water practices or design requirements for aircraft cargo
holds to reduce the chance of biological stowaways. Although there may be some
circumstances in which the ESA will play a role, Congress may see new laws more
directly and better suited to the prevention of introductions as also desirable.

54 For more information about the ESA generally, see CRS Issue Brief IB10072, Endangered
Species: Difficult Choices.

Federal Noxious Weed Act
Although most provisions in the Federal Noxious Weed Act of 1974 (P.L. 93-

629) were supplanted by the Plant Protection Act (see below), a key section (7 U.S.C.

§2814) still requires each federal agency to provide for noxious weed management
on lands under its jurisdiction. The provision, introduced in the 1990 Farm Bill (P.
L. 101-624, title XIV, §1453, 104 Stat. 3611) amended the Federal Noxious Weed
Act to require federal agencies to establish and fund noxious weeds management
programs through the agencies’ budgetary process. It also allowed the agencies to
implement cooperative agreements with state agencies regarding the management of
undesirable plant species in areas adjacent to federal lands. The Act requires joint
leadership from the Secretaries of Agriculture and of the Interior in coordinating
federal agency programs for control, research, and education associated with
designated noxious weeds. In 1994, a memorandum of understanding among several
federal agencies created the Federal Interagency Committee for Management of
Noxious and Exotic Weeds (FICMNEW) as a vehicle to coordinate noxious weed
priorities (see Interagency Efforts, below).
Nonindigenous Aquatic Nuisance Prevention and Control Act
The Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990
(NANPCA; Title I of P.L. 101-646; 16 U.S.C. 4701, et seq.) established a federal
program to prevent the introduction of, and to control the spread of, unintentionally
introduced aquatic nuisance species and the brown tree snake. The Coast Guard,
EPA, FWS, the Army Corps of Engineers, and the National Oceanic and
Atmospheric Administration (NOAA) share responsibilities for implementing this
effort, acting cooperatively as members of an Aquatic Nuisance Species (ANS) Task
Force to develop a program for protection, monitoring, control, and research. The
Task Force conducts studies and reports to Congress: (1) to identify areas where
ballast water exchange can take place without causing environmental damage; (2) to
assess whether aquatic nuisance species threaten the ecological characteristics and
economic uses of U.S. waters other than the Great Lakes; (3) to determine the need
for controls on vessels entering U.S. waters other than the Great Lakes; and (4) to
identify and evaluate approaches for reducing the risk of adverse consequences
associated with intentional introduction of aquatic organisms.55
Under NANPCA, state governors are authorized to submit (1) comprehensive
management plans to the Task Force that identify areas or activities for which
technical and financial assistance is needed; and (2) public facility management plans
to the Assistant Secretary of the Army (Civil Works) that identify public facilities for
which technical and financial assistance is needed. Grants are authorized to states
for implementing approved management plans, with maximum federal shares of 75%

55 See [] for accomplishments of the ANS Task

of costs for each comprehensive management plan, and 50% for each public facility
management plan.56
Under §1101 of NANPCA, a Great Lakes ballast water management program
(voluntary in its first 2 years) became mandatory in 1992. This section directed the
Coast Guard to issue regulations (33 CFR Part 151) to prevent the introduction and
spread of aquatic nuisance species into the Great Lakes through the ballast water of
vessels and established civil and criminal penalties for violating these regulations.
The Act also encourages the Secretary of Transportation, through the International
Maritime Organization, to negotiate with foreign countries on the prevention and
control of the unintentional introduction of aquatic nuisance species. In addition, the
Act directs the Corps of Engineers to develop a program of research and technology
for the environmentally sound control of zebra mussels in and around public
facilities, and make information available on these control methods. Subsequently,
the Corps established a zebra mussel facility research program, including annual
technical conferences and a publication series.
National Invasive Species Act
In 1996, the National Invasive Species Act (NISA; P.L. 104-332) amended
NANPCA to create a national ballast management program modeled after the Great
Lakes program wherein all ships entering U.S. waters (after operating outside the
U.S. Exclusive Economic Zone) are directed to undertake high seas ballast exchange
or alternative measures pre-approved by the Coast Guard as equally or more
effective. While initially unenforced on a ship-by-ship basis, this national program
was to have become mandatory within 3 years of the date the Coast Guard issued its
voluntary guidelines57 if ships did not show adequate compliance with the program58
in the absence of enforcement. The National Ballast Information Clearinghouse
(NBIC) was developed jointly by the Coast Guard and the Smithsonian
Environmental Research Center to synthesize, analyze, and interpret national data
concerning ballast water management. During the first 2 years (July 1999 through
June 2001), the NBIC found that nationwide compliance with ballast exchange
reporting requirements was low, with only 30.4% of vessels entering the U.S.
Exclusive Economic Zone (EEZ) filing reports with the NBIC.59 On March 4, 2002,
the Coast Guard published an advanced notice of proposed rulemaking, seeking
comments on development of a ballast water treatment goal and an interim ballast

56 Despite substantial authorizations, relatively little has been appropriated or made available
for state grants to implement these management plans.
57 64 Fed. Reg. 26672-26690, May 17, 1999. These regulations are effective July 1, 1999.
58 If the voluntary program does not result in sufficient compliance, reporting of ballast
water management practices will become mandatory for nearly all vessels entering U.S.
waters (33 CFR 151.2040). If necessary, the Coast Guard will promulgate further
regulations to implement such a mandatory reporting program.
59 G. M. Ruiz, et al., Status and Trends of Ballast Water Management in the United States:
First Biennial Report of the National Ballast Information Clearinghouse, (Edgewater, MD:
Smithsonian Environmental Research Center, Nov. 16, 2001), p. 4.

water treatment standard as part of regulations that would make guidelines for ballast
exchange mandatory.60
NISA encouraged negotiations with foreign governments to develop and
implement an international program for preventing the introduction and spread of
invasive species in ballast water. This Act required a Coast Guard study and report
to the Congress on the effectiveness of existing shoreside ballast water facilities used
by crude oil tankers in the coastal trade off Alaska, as well as studies of Lake
Champlain, the Chesapeake Bay, San Francisco Bay, Honolulu Harbor, the Columbia
River system, and other estuaries and waters of national significance. It also
authorized funding for research on aquatic nuisance species prevention and control
in the Chesapeake Bay, Gulf of Mexico, Pacific Coast, Atlantic Coast, and San
Francisco Bay-Delta Estuary.
Under NISA, a Ballast Water Management Demonstration Program was
established to promote the research and development of technological alternatives to
ballast water exchange. In addition, NISA modified the composition and research
priorities of the Aquatic Nuisance Species Task Force; and expanded the zebra
mussel demonstration program requirements. Research grants were required on
environmentally sound methods for controlling the dispersal of aquatic nuisance
species. In addition, the Corps of Engineers was directed to investigate and report to
Congress on methods specifically for preventing and reducing the dispersal of species
from the Great Lakes-Saint Lawrence drainage into the Mississippi River drainage
through the Chicago River Ship and Sanitary Canal. In addition, research was
authorized on the prevention, monitoring, and control of aquatic nuisance species in
Narragansett Bay, Rhode Island.
Finally, NISA required the Task Force to develop and implement a
comprehensive program to control the brown tree snake in Guam and other areas
where the species has spread outside of its historic range.
NISA has been criticized as inadequate and faulted for several alleged
shortcomings, including weakness in implementing some of its provisions.61 Since
NISA exempted most coastwise vessel traffic from ballast water exchange guidelines,
vessels traveling short distances (e.g., from San Francisco Bay, which is highly
invaded, to Puget Sound, which is less so), and therefore likely to be carrying live
organisms, are exempt from controls. With the exception of the Great Lakes, critics
point out that no ecological surveys or management actions have been funded for
inland waters such as the Colorado, Rio Grande, or Missouri Rivers. In addition,
they claim that sections of NISA pertaining to invasive plant management have not
been funded or used. Others are critical of the provisions of 16 U.S.C. 4711(k)(2)(A)
giving the vessel owner a blanket exemption to ignore any mandatory regulations if
the master determines that the vessel might not be able to safely conduct a ballast
water exchange on the open ocean. Whereas earlier provisions applicable to the

60 67 Fed. Reg. 9632-9638.
61 Letter of February 11, 1999, to Hon. Carol Browner, Administrator of Environmental
Protection Agency, from Representatives George Miller, Jim Saxton, and 16 other Members
of the U.S. House of Representatives.

Great Lakes provided a safety exemption, the master of a vessel was required to
report the problem to the Coast Guard and conduct alternate ballast water
management measures, often negotiated on a case-by-case basis. Critics believe the
NISA language has eliminated any incentive to change ballast water piping systems
or adopt other management or treatment options to deal with the problem safely.
Alien Species Prevention and Enforcement Act of 1992
This law (P.L. 102-393; 39 U.S.C. 3015) makes it illegal to ship certain
categories of plants and animals through the mail. The prohibited species are those
injurious animals whose movement is prohibited under part of 18 U.S.C. 42 and
those plants and animals whose shipment is prohibited under 16 U.S.C. 3372. (Both
sections are part of the Lacey Act.)
ASPEA does not make any new categories of plants or animals illegal to ship,
but rather makes it clear that use of the U.S. mail is included among those forms of
transport whose use is illegal for shipment of prohibited species. PEA appears to do
very little to prevent the introduction of non-native species, especially if the sender
is unaware that the shipped items are prohibited under the above laws, but ASPEA
does appear to add one more law to the arsenal under which prosecutors might bring
cases involving shipment of various species, including non-native species, to court.
Wild Bird Conservation Act of 1992 (WBCA)
The WBCA (P.L. 102-440; 16 U.S.C. 4901, et seq.) does not focus on the
prevention of invasions by non-native species, but rather on the conservation of birds
caught in the wild in foreign countries and imported into this country. By regulating
imports of certain wild birds, the WBCA may reduce imports of non-native parasites
and diseases that could affect wild populations of native birds. Prevention of
invasions would therefore be a potential effect of the law, rather than its purpose. It
also could reduce the chance that an imported wild bird species could escape, breed,
and increase to pest levels. Ten families of birds are specifically exempted from the
provisions of the law, though their importation could be restricted by many other
applicable U.S. laws.
Hawaii Tropical Forest Recovery Act of 1992
The Hawaii Tropical Forest Recovery Act (P.L. 102-574; 16 U.S.C. 4503(note))
amended the International Forestry Cooperation Act to create a variety of measures
to address the problems of the native forests of Hawaii. The introduction of such
non-native species as pigs, goats, and mosquitoes has been a major threat to the
integrity of native Hawaiian forest ecosystems, and the Act has several features that
address these issues. The Secretary of Agriculture is authorized to develop a program
to assist Hawaii and U.S. territories, through the Forest Service, to protect native
species from non-native species, and to establish biological control agents for the
non-natives. The Secretary must also develop plans for the Institute of Pacific
Islands Forestry and for the Hawaiian tropical forests which must, among other
things, provide for the study of biological control of non-native species.

In addition, the Act created a short-term task force of specified federal, state,
and other individuals. Among its other responsibilities, the task force was to develop
an action plan to “promote public awareness of the harm caused by introduced
species” and develop recommendations on “the benefits of fencing or other
management activities for the protection of Hawaii’s native plants and animals from
non-native species, including the identification and priorities for the areas where
these activities are appropriate.” The report has since served as the framework for
Forest Service management and research budget requests in this area. There has been
a modest increase in funds to support invasive species research and eradication
efforts, as well as a specialist to oversee management activities on invasive species.
Plant Protection Act of 2000
The Plant Protection Act of 2000 (PPA) (7 U.S.C. 7701 et seq.) consolidated
several plant quarantine authorities, some dating back to the 1880s. It gives the
Secretary of Agriculture the authority to prohibit or restrict the importation,
exportation, and the interstate movement of plants, plant products, certain biological
control organisms, noxious weeds, and plant pests.62 The statute also gives the
Secretary the authority to inspect foreign plant imports, to quarantine any state or
premise infested with a new pest or noxious weed, and to cooperate with states in
certain control and eradication actions. These authorities have been traditional
hallmarks of U.S. plant pest regulations, and are administered by APHIS in
collaboration with state departments of agriculture and their plant protection boards.
Traditionally, all states have some type of domestic quarantine laws but federal
regulations preempt state actions in interstate commerce. The new Plant Protection
Act, however, allows states to petition the Secretary for “special needs” exceptions
to federal rules. Exceptions granted by the Secretary would allow states more control
over movement of certain plant material across their borders. Regulations for
applying the new petition process have not yet been issued, but the Secretaries still
would retain the power to grant these “special need” petitions. The new law also
allows individuals or states to petition the Secretary of Agriculture to add or remove
plant pests from federal regulation. Regulation of foreign and interstate plant
movement has been important to prevent or limit the spread of a harmful non-native
species in the United States. The new law seeks to give more power to states to
influence the list of invasive species that would be federally regulated.

62 The PPA became law in June 2000 as part of the Agricultural Risk Protection Act (P.L.

106-224). This law consolidated and superceded several U.S. plant health laws, including:

(a) The Act of August 20, 1912 (commonly known as the “Plant Quarantine Act”, 7 U.S.C.

151-164a, 167); (b) The Federal Plant Pest Act (7 U.S.C. 150aa et seq. and 7 U.S.C. 147a);

(c) Section 102 (a) - (e) of the Department of Agriculture Organic Act of 1944 (7 U.S.C.
147a); (d) The Federal Noxious Weed Act of 1974 (7 U.S.C. 2801 et seq.), except sections
1 and 15 of that Act (7 U.S.C. 2801 note and 7 U.S.C. 2814); (e) the Joint Resolution of
April 6, 1937 (commonly known as the “Insect Control Act”) (7 U.S.C. 148 et seq.); (f) The
Halogeton Glomeratus Act (7 U.S.C. 1651 et seq.); (g) The Golden Nematode Act (7 U.S.C.

150 et seq.); and (h) Section 1773 of the Food Security Act of 1985 (P. L. 99-198; 7 U.S.C.

148f ).

The authority to impose quarantines has also been an important element of
federal plant protection statutes. History indicates, however, that the outcome of
domestic quarantines is seldom certain. For example, under the authorities of this
Act and preceding ones, APHIS has for decades imposed quarantines to prevent the
spread of imported fire ants, which can be harbored in the root balls of nursery plants
or in sod and soil; its geographical range, however, continues to expand. On the
other hand, the successful efforts to eradicate the Mediterranean fruit fly (medfly) in
California and Florida, and those to prevent witchweed from spreading into
Midwestern states attest to levels of success.
The PPA includes new authorities for controlling noxious weeds and for
regulating biological control agents. Under the PPA, states and others have a
statutory process to list or ‘delist’ pests and weeds based on ‘science-proven’ special
local needs. The Act expands the definition of noxious weed to include any plant
that could bring harm to agriculture, public health, navigation, irrigation, natural
resources, or the environment. This new definition could potentially allow federal
action on hundreds of invasive plant species not previously regulated. The old
Federal Noxious Weed Act allowed regulation of a limited number of invasive
weeds, restricting actions only against weeds “... new to, or not widely prevalent in
the United States.” Significantly, under the new law noxious weeds would now be
treated as other plant pests in respect to the declaration of emergencies. The
Secretary of Agriculture will have the authority to declare an emergency when a
newly introduced noxious weed poses a significant threat, and to transfer money from
other agencies or corporations of the Department (including the Commodity Credit
Corporation) to cover the cost of eradicating the weed.
The PPA also clarifies the extent of the Secretary’s authority to regulate
biological control agents and encourages the USDA, other federal agencies, and the
states to facilitate biological control of pests and other invasive species, whenever
feasible. The Act also provides USDA with guidance on how to regulate the
movement of biological control organisms, and authorizes USDA participation in
activities that enable the effective transfer of biological control techniques. Other
enhancements under the new law are: (1) harsher civil and criminal penalties for
smuggling illegal plants, or products that could harbor plant pests, noxious weeds,
or plant diseases; and (2) new authority to subpoena evidence and witnesses in the
prosecution of violators.
Executive Order 13112
President Clinton signed Executive Order 13112 on Invasive Species (64 Fed.
Reg. 6183, Feb. 8, 1999) on February 3, 1999, revoking President Carter’s 1977
Executive Order 11987 on exotic species.63 This Order seeks to prevent the

63 Although this Order is an attempt by the President to provide relief, such executive action
might not provide a final remedy. Executive action is limited by the authority provided for
in Article II of the Constitution, and no specific constitutional authority granted to the
President permits such action. Similarly, no act of Congress empowers the President to take
such executive action. Therefore, Executive Order 13112 could potentially be challenged

introduction of invasive species, provide for their control, and minimize their impacts
through better coordination of federal agency efforts under a National Invasive
Species Management Plan to be developed by an interagency National Invasive
Species Council (NISC). The NISC was directed to provide leadership, coordination,
oversight of federal agency activities, to encourage work with non-federal partners,
and to aid public participation. The Order directs all federal agencies to address
invasive species concerns, as well as refrain from actions likely to increase invasive
species problems.
The Secretaries of Agriculture, Commerce, and the Interior co-chair the Council.
In addition, the membership of the Council consists of the Secretaries of Defense,
Health and Human Services, State, Transportation, and Treasury as well as the
Administrators of the Agency for International Development and EPA. Along with
its many partners, the Council maintains a substantial website
[] which contains the plan and provides extensive
links to major data bases. There is a small staff, and the three lead Departments have
appointed liaisons to the Council.
The Executive Order also requires an advisory committee on which a wide range
of non-federal entities is represented. The advisory committee includes academics,
representatives of state and local governments; port authorities; the pet, nursery, and
pesticide industries; several environmental groups; a commercial fisherman; and a
rancher. The committee is divided into several working groups, which are co-chaired
by a member of the committee and a federal employee.
Some constituencies initially expressed concern about how the Executive Order
might affect their interests. Although rural agricultural groups have long been
involved in the control of invasive species, some elements of this constituency
criticized the Executive Order as an attempt to rule by decree and as a threat to rural
life and property.64 However, a search of websites of groups which had expressed
concern earlier suggests that by and large this concern is mentioned less frequently
now than when the Order was first issued. The pet and nursery industries are another
important constituency affected by the Order. Environmental groups have given
minimal attention to the Order, but have expressed particular concern about the threat
to biodiversity posed by non-native species.65

63 (...continued)
in the judiciary as a violation of the separation of powers. For more information on the legal
status of Executive Orders, see CRS Report 95-772 A, Executive Orders and Proclamations.
64 For an example of reaction from the property rights perspective on the perceived threat
posed by the Order, see: [] and
[ ht t p: / / www.l i ber t yma t t e r s .or g/ new_page m] .
65 Web sites on non-native species (with or without coverage of the Executive Order) by
environmental organizations include
[ h t t p : / / www.i gc.or g/ wr i / wr i / wr i / b i odi v/ gb f / gb f m]
and [].

Agency Responsibilities:
Programs and Implementation
These entries describe how
Homeland Security and Invasive Speciesfederal agencies address non-
native species concerns. Most of
Certain key agencies, including the Coastthese programs also address
Guard and that portion of APHIS having to doproblems of native pest species or
with port inspection, are to be transferred to theother domestic issues. No agency
new Department of Homeland Security. It isdevotes a large percentage of its
unclear how much emphasis the newresources to non-native species
department can be expected to place onissues. Even so, in some cases
interdiction or control of non-native species(e.g., APHIS), non-native species
whose entry could be characterized as mistakesaccount for a substantial portion
rather than attacks, and whose effects might beof the workload; in others (e.g.,
primarily economic or environmental ratherCoast Guard), non-
than acutely dangerous to society. Even so, anative species are a minor share
case could be made that the same precautionsof the total program. Outside of
designed to avoid bioterrorism could alsosome activities in the agricultural
reduce biological invasions whose origins aresector, no evidence was found of
not terrorists. The focus on terrorism is tooefforts in any agency to control
new to determine how it will affect invasivethe exports of U.S. species which
species problems.could become harmful or invasive
in the countries receiving them.
The management plan of the
National Invasive Species Council, while discussing improvements in international
cooperation in general terms, does not describe any specific agency tasks which the
United States itself might identify to prevent the spread of U.S. species that might
cause harm in other countries.
Interagency Efforts
National Invasive Species Council. The NISC and its member agencies,
supported by its advisory committee, was to develop recommendations for
international cooperation, promote a network to document and monitor invasive
species impacts, and encourage development of an information-sharing system on
invasive species. The Council released the first national invasive species
management plan (Meeting the Invasive Species Challenge) in January 2001, and
recommended nine goals for invasive species management. With the help of the
advisory committee, it also recommended research needs and measures to minimize
the risk of species introductions.66 The report constitutes the major federal attempt
to date to coordinate invasive species actions over a broad range of species and
habitats; across federal state, and local governments; and with private industry,
interest groups, and private individuals. Some of the major features in the three key
areas of prevention, early detection and rapid response, and control and management
are given below.

66 The plan is available at [].

Prevention actions in the plan include:
!An effort to increase APHIS and FWS inspections at ports of entry,
if resources permit.
!A division of actions into those required for prevention of (a)
intentional actions which may prove harmful and (b) unintentional
!By December 2003, the development of a risk-based comprehensive
screening system to evaluate first-time intentional introductions.
!By 2006, the development by federal agencies (with other interested
parties) of a phased-in evaluation process for intentional introduction
of (a) biological control agents for animal pests, (b) all non-native
freshwater or terrestrial organisms to Hawaii and insular territories;
and (c) non-native propagative plants, seeds, or land animals, or
aquatic organisms, regardless of purpose, to the continental U.S.
!For unintentional introductions, further control of pests in ballast
water and wood packing materials; identification of high risk non-
native species requiring special prevention effort; education of U.S.
travelers on the risks of returning with potential pests; and by 2003,
development of a system to evaluate and rank pathways of potential
introductions along with mechanisms to intervene and prevent them.
Early detection and rapid response actions in the plan include:
!Compiling a list of taxonomic experts, particularly where the need
(risk) is greatest.
!Developing methods to detect pathogens and parasites that may
affect the health of humans or any other species.
!Monitoring locations for likely introductions, e.g., ports, highways,
railroads, airports, construction sites, etc.
!Creating convenient systems to identify and report the presence of
invasive species to federal, state, tribal, and local governments, as
well as to share this and a variety of related information via the web
to interested parties, including the public.
!By 2003, the establishment (by NISC and other federal government
agencies) of a program to coordinate response to incipient invasions,
including interagency response teams having members with a range
of expertise.
!Testing detection and control methods to determine which are most
appropriate for potential invasions.

!Proposing revisions of current policies and procedures (e.g., for
quarantines, pesticide applications, interagency jurisdictional
questions, etc.) for compliance with current federal laws (e.g., ESA,
NEPA, Clean Water Act, etc.) as well as non-federal laws or
!For the FY2003 budget, developing and recommending to the
President legislation for rapid responses to incipient invasions and
possibly for permanent funding for rapid responses and for matching
grants to develop state capacities. (This has not yet been achieved,
although some legislation introduced in the 107th Congress would
have addressed some of these issues; within existing authorities,
NPS has already created emergency response teams for plant
invasions, but is markedly limited in its ability to work on any but
NPS lands; see discussion of NPS, below.)
Control and management actions in the plan include:
!Identifying and adopting sanitation methods to prevent the spread of
invasives (e.g., controlling the use of contaminated soils; requiring
pest-free mulch, sod, and ballast water; and restricting the transfer
of potentially contaminated fire-fighting or construction equipment).
!By January 2002, developing (by EPA) a proposal to cooperate
further with private industry for the use of pesticides to control
invasives, in a manner consistent with pesticide laws. (No such
proposal has been published as yet.)
!By January 2002, developing and proposing draft legislation (by
USDA) to the President to authorize matching funds for states to
manage invasive species and to control invasives on state or private
lands with the consent of the owner. (No such proposal has been
published as yet.)
!By January 2003, NISC to issue guidelines for ranking invasive
species control projects at local, regional, and ecosystem levels.
This plan is to be updated biennially to report on progress toward recommended
goals and objectives. The Council is to assess the effectiveness of this Order at least
once every 5 years, with a report to the Office of Management and Budget on
whether the Order should be revised.
Efforts to control invasive species have been remarkably bipartisan, with little
difference in approach between Republicans and Democrats, per se. While some
have advocated more or less spending for invasive species problems, differences tend
to be regional rather than partisan. Moreover, the transition between Administrations
does not appear to have changed the approach of the NISC or the agencies described
below in any readily discernable manner.

Aquatic Nuisance Species (ANS) Task Force. The ANS Task Force was
established in 1991, and is an intergovernmental organization dedicated to
implementing NANPCA by preventing and controlling aquatic nuisance species. The
Task Force, co-chaired by FWS and NOAA, coordinates government efforts related
to nonindigenous aquatic species in the United States with those of the private sector
and other North American interests. The Task Force consists of seven federal agency
representatives and 11 ex officio members. The other federal agencies are EPA,
Coast Guard, Army Corps of Engineers, USDA, and Department of State. Four
regional panels for the Great Lakes, the western region (17 western states), the Gulf
Coast, and the northeast serve as regional advocates and advisory committees to the
ANS Task Force to coordinate interagency efforts to address regional priorities. The
ANS Task Force approves comprehensive state and interstate plans for managing
nonindigenous aquatic species, permitting implementation efforts to receive federal
funding. There are currently nine state/interstate plans that have been approved (see
State Efforts below) and 11 states/tribes receive cost-share grants from the FWS to
implement components of the plans. The Task Force recently initiated a public
awareness campaign targeted toward aquatic recreation users entitled “Stop Aquatic
Hitchhikers”. The campaign builds on voluntary recreational activities guidelines to
highlight measures that can be taken to minimize the spread of aquatic invasive
speci es. 67
Federal Interagency Committee for Management of Noxious and
Exotic Weeds (FICMNEW). This Committee was created through a memorandum
of understanding among agency heads in August 1994.68 It is composed of agency
representatives from 16 federal agencies with invasive plant management and
regulatory responsibilities, including: the Departments of Agriculture, the Interior,
Transportation, Defense, and Energy as well as EPA. FICMNEW fosters cooperative
work on integrated ecological approaches to management of noxious and exotic
weeds on federal lands and provides technical assistance on private lands. Recent
accomplishments include publication of a weed fact book, Invasive Plants: Changing
the Landscape of America, as well as the document Pulling Together: National
Strategy for Invasive Plant Management.
Department of Agriculture
The Department of Agriculture has a variety of programs affecting invasive
species. Agencies of the Department, along with the Departments of Commerce and
the Interior, are working to prepare a cross-cutting budget for invasive species
spending in FY2004.
Agricultural Research Service (ARS). ARS provides scientific and
technical support for USDA’s regulatory agencies, including APHIS. In FY2002,
APHIS transferred about $10 million of its appropriation to ARS for research on such
things as detection technology for ports of entry, systematics for rapid identification

67 See []; the ANS Task Force also manages a website at
[] .
68 FICMNEW manages a website at [].

of invading species, and pesticide application technology. In addition, ARS, under
its FY2002 appropriation, is allocating $107.9 million to research on invasive
species, and $119.8 million to research on integrated pest management (IPM) and
biological controls for invasive pests and weeds, including helping to monitor target
pests of IPM programs (e.g., ground, aerial, and satellite monitoring of leafy spurge
and other weed species).
Among ARS’s recent research accomplishments on invasive species are:
!identification of a parasite that would destroy outbreaks
of papaya mealybugs, an invasive species from the
Caribbean which has recently become established in
!implementation of a 5-year research and demonstration
program to reduce leafy spurge on rangeland using
combined biological control and integrated grazing
!investigation of a chemical attractant that could
facilitate detection of the Asian longhorned beetle;
!development of the first biological control agent (a
weevil) to eradicate the invasive Melaleuca tree;
!discovery that certain short-lived herbicides effectively
control hydrilla and Eurasian watermilfoil in lakes, with
little environmental impact.
Animal and Plant Health Inspection Service. APHIS is responsible for
approximately 78% of total federal spending on invasive species in FY2002. (See
Appendix B.) The agency conducts preclearance activities, treatment programs,
detection surveys, and eradication efforts to prevent the introduction of specific
foreign pests that would threaten U.S. agricultural production and natural ecosystems
through an agriculture quarantine inspection program conducted at 178 U.S. ports of
entry. These foreign pests include insects, plant and animal diseases, mollusks,
mites, and invasive plants. Domestically, APHIS cooperates with federal and state
agencies as well as non-governmental organizations to detect, contain, and eradicate
infestations of selected foreign pests before they become well-established and spread.
APHIS may use integrated management approaches including biological control to
address widespread insects, diseases, and selected weeds that cannot otherwise be
eradicated.69 The majority of APHIS’s relatively small budget for non-native species
concerns is devoted to border control, with relatively little expended for treatment of
infested sites.70
Under agency interpretations of NEPA, APHIS may approve and issue permits
for importing nonindigenous species (7 CFR 372.5(b)(4)) following preparation of
an environmental assessment rather than an environmental impact statement. Permits
for importing nonindigenous species into containment facilities (7 CFR

372.5(c)(3)(iii)(A)) and for interstate movement of nonindigenous species between

69 The APHIS home page is [].
70 For more information see [].

containment facilities (7 CFR 372.5(c)(3)(iii)(B)) are categorically excluded from the
agency’s NEPA requirements.
Within APHIS, Wildlife Services addresses a variety of problems related to
wildlife damage of agriculture and other affected industries. While the targets of
these control efforts commonly are native species such as coyotes, Canada geese, red-
winged blackbirds, etc., non-native animals may be affected as well. If non-native
animal populations reach levels that threaten aircraft takeoffs and landings, increase
the spread of wildlife-borne diseases, harm threatened or endangered species, or
threaten loss of life, habitat or food supply of other species, the Service may provide
assistance. In general, its work focuses on target organisms after they reach problem
levels, rather than immediate control after the initial discovery of a non-native.
Among the recent activities of APHIS regarding prevention and control of
invasive species are:
!continued detection and delimitation (and an attempt at eventual
elimination) of the Asian longhorned beetle, using $30 million in
emergency funds;
!successful reductions of stands of Dalmatian toadflax, leafy spurge,
and purple loosestrife using leaf-eating, stem-boring, or root-galling
exotic insects that infest only the target species;
!cooperation with the U.N. Food and Agriculture Organization (FAO)
and the Caribbean Community in a regional program to prevent the
tropical bont tick, which could introduce heartwater and
dermatophilosis diseases into wildlife and livestock populations,
from entering the United States and its territories.
Cooperative State Research, Education, and Extension Service
(CSREES). CSREES is the USDA agency that distributes federal funds to support
research and extension programs at the land grant colleges of agriculture in every
state. CSREES allocates some funds to each state according to formulas spelled out
in authorizing laws, and distributes the rest through various competitive grant and
earmarked grant programs. State-level research on invasive species, and extension
programs to help farmers, ranchers, and other residents adopt cost-effective,
environmentally safe controls for invasive species, are supported through one or more
of these means.
Economic Research Service (ERS). ERS, the USDA’s economic research
agency, contributes to the Department’s invasive species efforts through the pesticide
use and pest management economic research and analysis program. This program
provides information that is used to administer the integrated pest management
program, Food Quality Protection Act implementation, and invasive species
programs. The agency has not focused any research specifically on invasive species
in 2001 and 2002. However, the Bush Administration’s FY2003 budget request
proposed a $2 million increase to support an ERS project that would examine the
economic effects of invasive species on crops, livestock, commodity markets, trade,

and regional economies, and evaluate the benefits and costs of various approaches
to preventing the introduction of, or eliminating, those species.
Farm Service Agency (FSA). In managing the Conservation Reserve
Program, FSA requires all participants to control weeds (including noxious weeds),
insects, pests, and other undesirable species on enrolled lands.
Forest Service (FS). The FS manages 192 million acres of federal lands for
many values, including protection from invasive weeds. It also is the USDA agency
that conducts the greatest amount of nuisance weed control. To support these efforts,
the FS conducts research focused on invasive plant species, including ecological
studies to support restoration of sites after treatment of exotic weeds, as well as
control of: Miconia sp. and other invasive plants in Hawaii; kudzu in the southern
United States; yellow starthistle, spotted knapweed, and leafy spurge in Idaho; and
more. In addition, the FS seeks to control and mitigate the impacts from harmful
non-native insects, such as the Asian longhorned beetle, gypsy moth, hemlock woolly
adelgid, and browntail moth. The agency conducts research on such tree diseases as
butternut canker and sudden oak death syndrome, and works to find and develop
trees genetically resistant to Dutch elm disease, pitch canker, chestnut blight, and
white pine blister rust. The FS works closely with state agencies, private landowners,
and tribal governments on prevention and control activities, and provides funding and
technical assistance through its state and private forestry programs.
The Administration’s FY2003 budget request proposed an increase of $1.2
million for an emergency fund that could be used for rapid responses to new
introductions of non-native or invasive pests or diseases for which no previous
federal funding has been available.
Natural Resources Conservation Service (NRCS). NRCS provides
technical assistance to cooperating landowners and federal agencies (such as the
Forest Service and Bureau of Land Management) on adopting conservation practices
on agricultural land, including rangeland. The agency operates 22 Plant Materials
Centers that seek to use plants to solve conservation problems. The Centers are
conducting 54 studies nationwide that strive to control or suppress weeds, and 146
studies focused on finding suitable replacements for invasive species once control is
achieved. Some of the target weeds in this effort are yellow starthistle, cheatgrass,
knapweed, Canada thistle, and cogongrass. The Plant Centers also promote the use
of native species on the more than 30 million acres enrolled in the Conservation
Reserve Program, a multi-year land retirement program.
Department of Commerce
The Department of Commerce has a variety of programs affecting invasive
species. Agencies of the Department, along with the Departments of the Interior and
Agriculture, are working to prepare a cross-cutting budget for invasive species
spending in FY2004.
National Oceanic and Atmospheric Administration (NOAA). NOAA
is the statutory co-chair of the interagency Aquatic Nuisance Species Task Force and
has been delegated responsibility from the Department of Commerce to be the co-

chair of the National Invasive Species Council. Through both the Sea Grant program
(see below) and a ballast water management technology development program,
NOAA has funded research on alternatives to ballast water exchange as methods of
ballast water management. NOAA line agencies, including the National Ocean
Service and the National Marine Fisheries Service, have been involved in both
prevention and control activities. The National Ocean Service has begun an effort
to monitor coastal areas for the presence of nonindigenous species.
NOAA’s Great Lakes Environmental Research Lab (GLERL) targets two
components of the invasive species issue: (1) prevention and control to stop the
inflow and spread of new aquatic organisms, with particular emphasis on ship ballast
and (2) understanding and minimizing the ecological and economic impacts of recent
species invasions, especially the on-going secondary effects of zebra mussels.71 The
lab’s current research program reflects both priority areas: GLERL developed and
provides leadership for the Great Lakes NOBOB (no-ballast-on-board) and Ballast
Exchange research program (biological assessment of ballast tank residuals,
experimental determination of effectiveness of ballast exchange) with combined
funding from NOAA and several other agencies. In this program, GLERL scientists
collaborate with scientists at several universities and the Smithsonian. In a related
project, scientists at GLERL and the University of Michigan are evaluating two
chemicals for use on residuals in NOBOB tanks. GLERL also leads investigations
of invasive species impacts on the Great Lakes ecosystem, focusing on zebra mussels
and other recent invaders. One project studies whether recent changes in the food
web of the southern basin of Lake Michigan were caused by nonindigenous species.
Another project examines the impacts on fish communities in the Great Lakes as a
result of recent invasions. In FY2003 GLERL will start a new project to develop a
model of ballast tank flow during ballast tank exchange.
National Sea Grant College Program. Sea Grant programs on invasive
species focus on marine systems and the Great Lakes, through funding of research,72
education, and outreach to address threats from invasive species. Specific research
is supported on the biology and life history of non-native species; impacts of invasive
species on ecosystems, including socioeconomic analysis of costs and benefits;
control and mitigation options; prevention of new introductions; and reduction in the
spread of established populations of harmful non-native species. Where success has
been achieved in invasive species management efforts in coastal and Great Lakes
states, Sea Grant programs have been critical. In addition, Sea Grant funded a 3 year
Nationwide Zebra Mussel Training Initiative that allowed Sea Grant professionals
to provide services outside the coastal and Great Lakes areas. This Initiative was
instrumental in providing inland states with a knowledge base for creating state and
regional programs.

71 See [].
72 The Sea Grant Program manages an Aquatic Nuisance Species Clearinghouse website at
[ h t t p : / / www.a qua t i c i n va de r s .or g/ ] .

Department of Defense
The Department of Defense (DOD) engages in management and control of
invasive non-native species. It is promulgating joint regulations with the
Environmental Protection Agency covering discharges from DOD vessels. These
regulations (40 CFR 1700) implement §312(n) of the Clean Water Act. When
complete, they will set discharge standards for vessel ballast water to address the
environmental effect of non-native species introduction via that ballast water (as well
as addressing chemical pollution from other Armed Forces vessel discharges). The
regulations are being developed in three phases. The first, completed in May 1999,
determined which ballast-water discharges would require control. The second,
currently in progress, will set performance standards, and the third will promulgate
regulations for meeting those standards. The Armed Forces Pest Management Board
coordinates DOD activities to prevent and control the spread of invasive species,
including the brown tree snake and noxious weeds, on, to, or from military bases.
Army Corps of Engineers. The Army Corps of Engineers supports a range
of invasive species efforts. The Aquatic Plant Control Program provides cost-shared
(50%) assistance to states in managing aquatic plants in non-federal waters. The
Environmental Research Laboratory administers an Aquatic Plant Control Research
Program, which develops methods to assess and manage invasive aquatic plants. The
laboratory also administers a zebra mussel research effort to develop control
measures. The Corps fully funds control of aquatic plants, predominantly for
invasive species, in waterways in certain southeastern states through the Removal of
Aquatic Growth (RAG) Program. It is also conducting a Chicago Channel Dispersal
Barrier Study to determine effective measures to limit the dispersal of harmful non-
native species. The Corps also assists in the broader DOD initiatives described
Department of the Interior
The Department of the Interior (DOI) has a variety of programs affecting
invasive species. Agencies of DOI, with the Departments of Commerce and
Agriculture, are working to prepare a cross-cutting budget for invasive species
spending in FY2004.
Bureau of Indian Affairs (BIA). The Bureau of Indian Affairs is responsible
for protecting and improving the trust assets of Indian tribes while maintaining a
relationship within the spirit of self-governance. The BIA, through exotic weed
eradication and other programs, helps support the management of non-native species
on Indian lands (e.g., reservations, pueblos, rancherias, communities). Its Noxious
Weed Control program is the focus of its efforts (see Appendix B for spending
levels). The program provides matching grants to tribes for weed control in the
BIA’s 12 regions. It has no national program for harmful non-native animals,
although some tribes work with the Forest Service for control of such insect pests as
gypsy moths and other forest insect pests; funding for these programs comes through
the Forest Service. Agency officials have not been major participants in the activities
of the NISC.

Bureau of Land Management (BLM). BLM focuses its non-native species
efforts primarily on controlling invasive plants, especially on the 264 million acres73
it manages, primarily in western states and Alaska. BLM’s action plan, Partners
Against Weeds, details their strategy to prevent and control the spread of noxious
weeds on public lands; the seven goals of the plan roughly parallel those of NISC.
BLM instituted a Communication and Environmental Education Plan to help prevent
and control the spread of noxious weeds on public lands, and adopted policies to
address weed infestation. Current BLM studies address biological, chemical, and
physical treatment protocols for invasive plants in the western United States. In
addition, BLM has the somewhat conflicting role of protecting and managing wild
horses and burros which, although not native, have a legally protected status.
APHIS, through its Wildlife Services program, regulates animal pests (primarily
predator control) on BLM land under a Memorandum of Understanding between
On its grazing lands, BLM requires that non-native plant species be used only
when native species are not available in sufficient quantities or are incapable of
maintaining or achieving properly functioning conditions and biological health.
Bureau of Reclamation (BOR). The research, prevention, detection, and
control programs of this agency address the pests of aquatic systems such as canals,
reservoirs, pipelines, and rivers. Such species include both plants and animals, e.g.,
hydrilla, Eurasian watermilfoil, zebra mussels, and Asian river clams. Their presence
results in loss of irrigation water, impediments to navigation, and lost recreational
opportunities. BOR works with other federal agencies, state and local governments,
and others to control these pests. Methods include biological control agents and
pesticide application. Projects include, among other things, insect biological control
for five weed species; grass carp (itself a non-native species) for control of certain
aquatic weeds, and use of herbicide meters to match herbicide flow to fluctuating
water levels. The agency also maps the movement of certain invasive species (e.g.,
populations of Salvinia molesta (an aquatic weed), hydrilla, and zebra mussels), and
works with cooperators in Cooperative Weed Management Areas in western states
to identify and control weeds. It works to improve control methods and basic
knowledge of non-native species, and to develop methods to restore areas of salt
cedar infestation. BOR works with Mexican officials on cross-border weed
Fish and Wildlife Service (FWS). FWS focuses its efforts on preventing
the introduction and spread of invasive species and, where feasible and warranted,
on controlling established non-native species. Its authority to protect domestic
ecosystems is indirect or general, meaning the agency sometimes finds itself at odds
with other interests, particularly those wishing to introduce various species for sport
fishing or hunting. Its broad authority under the Endangered Species Act gives it
some authority if a proposed introduction or other activity seems likely to harm a
protected species. Its spending on harmful non-native species occurs in five of its
programs: habitat conservation (coastal program), Partners for Fish and Wildlife

73 BLM’s website is at []. For the PAWs
program, see [].

(including some funding earmarked by Congress for special projects), refuge
operations and maintenance, fisheries (including the Aquatic Nuisance Species and
brown tree snake programs), and international affairs.
In FY2003, FWS proposes to allocate $3.7 million nationally to control invasive
plants and animals on the 93 million acre National Wildlife Refuge System (NWRS).
Many refuges spend substantial portions of their budgets on the control of such non-
native species as pigs, melaleuca, salt cedar, purple loosestrife, etc. The agency
attempts to minimize the use of pesticides and herbicides in these efforts. A full-time
national coordinator works with regional coordinators and refuge staff and
government officials of other agencies and levels.
FWS is working with the USGS to survey the units of the National Wildlife
Refuge System for more specific information about invasive species problems at all
units. The data will be compiled into a central database called the National
Biological Information Infrastructure (NBII; see USGS, below) to facilitate early
detection and predictive modeling efforts for invasives in each Refuge.
Geological Survey (USGS). The Biological Resources Division of USGS
focuses on researching factors influencing invasion by non-native species and the
effects of invasive species on ecosystem processes, native species, and landscape
dynamics, especially on Department of the Interior lands. Through the National
Biological Information Infrastructure, USGS works to document, disseminate, and
integrate information about the nation’s biological resources generally, including its74
nonindigenous species. USGS has focused on a small number of highly invasive
species in the Great Lakes and eastern waterways and wetlands, in riparian
ecosystems, and in Hawaii and Florida, as well as invasive plants on western
rangelands. USGS also manages the national Nonindigenous Aquatic Species
Database, as well as several regional databases (e.g., Hawaii, Colorado plateau, and
northern prairie) and manages a nonindigenous aquatic species website.75
National Park Service (NPS). Approximately 200 NPS units (e.g., national
parks, national monuments, preserves, national lakeshores and seashores, national
scenic trails, national historic sites and parks, et al.) of the over 375 NPS units have
identified, in their resource management plans, exotic species as a significant
resource management concern. The NPS uses integrated pest management to manage
exotic species. Fences are constructed to prevent exotic pigs, goats, and cattle from
entering sensitive areas or spreading invasive species to parts of other parks. For
example in Hawaii, NPS designates Special Ecological Areas that best represent
Native Hawaiian systems, fences these areas, and then removes exotic species from
them. Theodore Roosevelt National Park and Devils Tower National Monument are
serving as insectaries where biocontrol agents are harvested and made available to
surrounding landowners.
NPS has special regulations to minimize the potential for spreading zebra
mussels and other aquatic nuisance species at the St. Croix (Wisconsin) National

74 Information on the project is found at [].
75 The website is at [].

Scenic Riverway (36 CFR 7.9), where aquatic nuisance species is defined as
meaning the zebra mussel, purple loosestrife, and Eurasian water-milfoil. In the
western United States, NPS finds leafy spurge and knapweed to be among the most
problematical non-native species, while concern increases further west for Japanese
brome (Bromus japonica) and cheat grass (B. tectorum).
NPS regulates fishing on its lands (36 CFR 2.3(d)(2)) and prohibits the
possession or use of live or dead minnows or other bait fish, amphibians, non-
preserved fish eggs or fish roe, as bait for fishing, except in designated waters.
Waters which may be so designated are limited to those where non-native species are
already established, where scientific data indicate that the introduction of additional
numbers or types of non-native species would not hurt populations of native species,
and where park management plans do not call for elimination of non-native species.
NPS Rapid Response Teams. In FY2001, NPS created Exotic Plant
Management Teams for rapid response to invasive plants on units of the National
Park System. The teams are explicitly modeled on teams used to fight fires. The
current 9 teams may increase to 16, if funding permits. In their FY2001 report, the
teams claimed elimination of two invasive plant species at Haleakala National Park
and of all exotic plants at Loggerhead Key at Dry Tortugas National Park, among
other accomplishments. Lake Mead National Recreation Area is serving as the focal
point of an Exotic Plant Management Team whose tasks include controlling salt
cedar. The team approach provides quick response and consistent application of
techniques, provides a personnel resource not available to these parks, and reduces76
the need of individual parks to procure and maintain expensive equipment.
In contrast to interagency fire suppression efforts, current law does not authorize
these teams to be shared with other agencies for work on non-federal or other federal
lands, although NPS teams do train personnel from other federal agencies with these
methods. Despite this problem, the current nine NPS teams do work with many
partners, ranging from National Wildlife Refuges, Florida Power and Light, and the
Nature Conservancy to coordinate plant pest control and eradication efforts.
Office of Surface Mining Reclamation and Enforcement (OSM).
OSM, in certain situations, allows the use of introduced species in revegetating
reclamation sites (30 CFR 715.20(b), 717.20(b), 816.111(b)(5), and 817.111(b)(5)),
directing that introduced species be substituted for native species only if appropriate
field trials have demonstrated that the introduced species are equal or superior to
natives for the approved post-mining land use, or are necessary to achieve a quick,
temporary, and stabilizing cover. Such species substitution must be approved by
OSM. Introduced species must meet applicable state and federal seed or introduced
species statutes, and must not include poisonous or potentially toxic species.
Western states have particularly attempted to avoid introducing invasive species on
reclaimed minelands. Less attention has been given to the problem in the east,

76 For more on the teams, see []. It appears that no similar
teams function to control invasion of exotic animals, such as lake trout at Yellowstone Lake;
animal invasions continue to be handled on an ad hoc basis.

although Kentucky has experienced serious problems with kudzu. For more
information about OSM, see: [].77
Department of State
The Department of State works with other federal agencies, states, tribes, non-
governmental organizations and the private sector to develop U.S. foreign policy on
invasive species, which it then seeks to integrate into international agreements such
as the Convention on Biological Diversity.78 The Department also is negotiating with
the International Maritime Organization to develop a plan to control the spread of
invasive species from exchange of ships’ ballast water. The State Department’s
Bureau of Oceans and International Environmental and Scientific Affairs is striving
to increase international awareness of invasive species through a series of regional
workshops. The workshops aim to facilitate regional cooperation on strategies to
address this cross-sectoral international problem.
Department of Transportation
Coast Guard. Under the Non-Indigenous Aquatic Nuisance Prevention and
Control Act (NANPCA), the Coast Guard is responsible for developing and
implementing a ballast water management (BWM) program to prevent the
unintentional introduction and dispersal of nonindigenous aquatic species into waters
of the United States from ship ballast water. This is presently accomplished through
a mandatory BWM program for the Great Lakes ecosystem and voluntary guidelines
for the remainder of U.S. waters. Relevant regulations are published at 33 CFR Part

151, Subparts C and D.

As stated in the Secretary of Transportation’s June 2002 Report to Congress on
the effectiveness of the voluntary BWM program, the Coast Guard plans to develop
regulations requiring active BWM of all ships that enter U.S. waters after operating
beyond the Exclusive Economic Zone, and will establish sanctions for failure to
comply. The Coast Guard will also continue its efforts to establish a quantitative
ballast water treatment (BWT) performance standard; protocols for testing, verifying
and reporting on BWT technologies; and a program to facilitate experimental
shipboard installation and operation of promising BWT technologies.
Federal Aviation Administration (FAA). FAA personnel, in coordination
with APHIS, worked with Hawaiian transportation officials to develop a risk
management plan for the Kahalui Airport, Maui, to minimize the potential for brown
tree snakes and other invasive species to arrive via aircraft. Internationally, FAA
(with support from APHIS) initiated efforts and prompted the International Civil
Aviation Organization to pass a resolution encouraging pre-boarding education and

77 For more information about OSM, see []. This site provides
information about OSM generally, and has some information about the agency’s attempts
to conserve native plants species. As of September 2002, there appeared to be no entries on
strategies to avoid spreading invasive species per se.
78 However, the United States is not a signatory to this treaty.

screening as well as other means to reduce the risk of introducing potentially invasive
species by commercial aircraft.
Federal Highway Administration (FHwA). Direct activities by the FHwA
focus primarily on research, guidelines, and conferences to help state transportation
departments prevent and combat roadside invasive species. Vegetation management
activities are state-funded and the FHwA does not participate directly in those
Executive Office of the President
Council on Environmental Quality (CEQ). The Council on
Environmental Quality assists in formulating agency guidance in integrating issues
involving non-native invasive species in the process of implementing NEPA. CEQ
coordinated and led the Clinton Administration’s efforts on developing Executive
Order 13112 on Invasive Species.
Office of Science and Technology Policy (OSTP). OSTP was involved
in reviewing different issues and options as well as developing a white paper for the
Clinton Administration’s Executive Order 13112 on Invasive Species. The
Committee on Environment and Natural Resources (CENR) of the President’s
National Science and Technology Council (NSTC), which is administered through
OSTP, identified invasive species as a priority research focus and established an
interagency Task Team on Invasive Species. Representatives from several federal
agencies serve on CENR, including Defense, EPA, Interior, NOAA, NSF, USDA,
the Smithsonian, State, Transportation, and the Council on Environmental Quality.
E.O. 13112 specifically directs the National Invasive Species Council to work with
Office of the United States Trade Representative (USTR). USTR may
play a limited consultative role in instances where invasive species concerns may
arise in relation to international trade agreements.
Independent Agencies
Environmental Protection Agency. The Environmental Protection Agency
(EPA) is a member of the National Invasive Species Council and actively participates
in implementing the invasive species management plan. EPA conducts and supports
research on the prevention, early detection, control, and management of invasive
species. For example, Agency scientists are working with investigators at the
University of Kansas to develop models to identify the potential niche for non-native
species. Model results are used to estimate the area and spreading rates for
potentially invasive species. These same models are being used to evaluate the
impact of climate change on the invasiveness of non-native species. Additional
efforts within EPA’s Office of Research and Development (ORD) are focused on
developing methodologies for the early detection of non-native invasive species and
approaches for applying those methodologies in existing environmental monitoring
programs. ORD investigators are also working with regional staff to develop

guidance for including evaluations of the potential impacts of invasive species in
NEPA assessments.
In addition to these active research programs, EPA is involved internationally
in cooperative efforts focusing on the early detection and rapid response to potential
invasive species. These efforts are mainly coordinated from the Agency’s regional
offices surrounding the Great Lakes and regional offices in the Northeast and involve
considerable collaboration and cooperation with Canadian environmental resource
managers. As part of these international efforts, EPA is designing public awareness
programs to educate stakeholders and the public about the risks and impacts of
invasive species. Invasive species public awareness programs are also sponsored by
various estuarine management groups who participate in the Agency’s Office of
Water, National Estuary Program (NEP).
National Science Foundation. The National Science Foundation funds
basic and applied research on invasive species, including their roles in population and
ecological processes, their relationship to biological conservation activities, and their
role as a disturbance agent in ecosystems.
Smithsonian Institution. The Smithsonian Environmental Research Center
(SERC) performs research on invasive species in coastal ecosystems. SERC collects
and analyses data and reports on such species to determine patterns of transfer,
invasion, and impact. Specific projects examine patterns of ballast-water delivery;
test the susceptibility of marine communities to invasive species; document the
history of alien species invasions for Chesapeake Bay; establish a national database
on nonindigenous marine and estuarine species; measure ecological impacts; and
measure species transfer associated with shipping. In cooperation with the Coast
Guard, SERC established the National Ballast Water Information Clearinghouse to
measure the changing patterns of ballast water delivery and management for vessels
arriving in U.S. ports and to synthesize national data on patterns and impacts of alien
species in coastal ecosystems. Aquatic and terrestrial invasive species research is
also conducted by the Smithsonian Institution’s National Zoological Park, the
Smithsonian Tropical Research Institute, and the National Museum of Natural
State Efforts
This report focuses on federal programs and policies dealing with non-native
species and does not discuss the extensive efforts of individual states to deal with
these concerns. State efforts on this issue are highly variable. For examples of state
programs addressing invasive species, see:
Virginia [];
Michigan [,1607,7-135-3313_3677_8314---,00.html];
Wisconsin [];
Hawaii [];
Florida []; and
California [].

For additional information on state and local programs addressing non-native species
concerns, see p. 201-231 of the 1993 OTA Report Harmful Non-Indigenous Species
in the United States.
Under the NANPCA, nine state/interstate aquatic nuisance species management
plans to guide efforts had been completed and submitted to the federal government
by mid-2002.79 In addition, two state plans (Massachusetts and Wisconsin) have
completed the public comment process and are nearly ready for submission by the
state governors. An additional three states (Montana, Maine, and Alaska) have plans
currently in the state public comment process. States in the earlier stages of
developing plans include Idaho, California, Arizona, Texas, Louisiana, South
Carolina, Hawaii, and Maryland. Despite substantial federal authorizations,
relatively little has been appropriated or made available for grants to implement these
state management programs.
International Efforts
Non-governmental organizations have been active in focusing international
attention on the problems of non-native species introductions. In 1988, the European
Inland Fisheries Advisory Commission (EIFAC) and the International Council for the
Exploration of the Sea (ICES) published Codes of Practice and Manual of Procedures
for Consideration of Introductions and Transfers of Marine and Freshwater
Organisms, which subsequently was modified by ICES to include genetically
modified organisms.80
In July 1991, the International Maritime Organization’s (IMO’s) Marine
Environmental Protection Committee (MEPC) issued voluntary “International
Guidelines for Preventing the Introduction of Unwanted Aquatic Organisms and
Pathogens for Ships’ Ballast Water and Sediment Discharges.”81 Adopted by a
diplomatic conference of the IMO in 1993, IMO-member states were requested to
follow these guidelines, which also called for exchange of ballast water in the open
ocean (to reduce transfer of species from port to port). A review conducted by
Australia in 1993 revealed that few countries had implemented the guidelines. In
1994, the MEPC established a ballast water working group to draft regulations for
the control and management of ships’ ballast water. These draft regulations were
debated at the November 1998 and June 1999 MEPC meetings. Consideration will
be given by the IMO to adopting these management protocols as a formal IMO

79 New York, Michigan, Ohio, St. Croix River (Minnesota and Wisconsin), Washington,
Iowa, Illinois, Lake Champlain Basin (New York and Vermont), and Oregon. For details
of these plans, see [].
80 International Council for the Exploration of the Sea. ICES Code of Practice on the
Introductions and Transfers of Marine Organisms. 1994. Copenhagen, Denmark. 5 p.
81 []

instrument.82 If adopted, the instrument would require all ratifying member nations
to follow the regulations, which would include open-ocean exchange.
Several international agreements and codes of conduct address non-native
species. For example, Article VI of the International Plant Protection Convention
focuses on regulated pests, establishing an international system using inspections and
quarantines to prevent the dissemination of pests affecting plants.83 In 1995, the
members of the Food and Agriculture Organization of the United Nations (FAO)
adopted the Code of Conduct for Responsible Fisheries, which complements the
Convention on Biological Diversity and contains several sections on the responsible
use of non-native species in fisheries and aquaculture.84 A key aspect of the Code of
Conduct for Responsible Fisheries, as well as the Convention on Biological
Diversity, is the adoption of a “precautionary principle”85 to development. FAO and
the Government of Sweden elaborated operational guidelines for this approach in
relation to capture fisheries and species introductions.86 Member States of FAO are
now working to promote and implement these guidelines. To assist in the
responsible use of aquatic introductions, FAO maintains an interactive website and
database on introductions of aquatic species that contains an annotated registry of
introductions that includes some of their ecological and social impact, the reason for
the introduction, and who was responsible for the introduction.87
In 1996, the International Union for the Conservation of Nature (IUCN)
developed and released the document Draft IUCN Guidelines for the Prevention of

82 As of the date of this report, it is uncertain whether the new instrument will be an Annex
to the International Convention on Marine Pollution (MARPOL), a new convention, or a
code of conduct. For additional details on these negotiations, see
[ ].
83 []
84 []
85 This principle, exemplified in the expression “better safe than sorry,” can be loosely
defined as applying to situations when potential harm is serious and irreversible, though full
scientific certainty is lacking. In such instances, the precautionary principle would have
regulators act to reduce (or eliminate) the harm while weighing the probable costs and
benefits of acting or not acting. The precautionary principle is not the sole purview of one
side of the debate, and if applied to more than one goal (e.g., community stability and
species preservation) may point to multiple and contradictory choices. For discussions of
the precautionary principle, see Poul Herremoës, et al., eds., Late Lessons from Early
Warnings: the Precautionary Principle 1896-2000, European Environment Agency, Report
No. 22; and Vern R. Walker, “Some Dangers of Taking Precautions Without Adopting the
Precautionary Principle: A Critique of Food Safety Regulation in the United States,”
Environmental Law Reporter, v. 31 (2001): 10040-10047. A significant aspect of the debate
on this issue, particularly in the regulation of pollution, is what level of knowledge is needed
about potential harm to justify action.
86 FAO. Precautionary Approach to Fisheries. Part 1: Guidelines on the Precautionary
Approach to Capture Fisheries and Species Introductions. FAO Fish. Tech. Paper 350/1,
(Rome, FAO: 1995).
87 FAO Database on Introductions of Aquatic Species (DIAS) at
[ h t t p : / / www.f a o.or g/ f i / d ef aul t . asp] .

Biodiversity Loss Due to Biological Invasion. It focused on recommendations for
reducing the risks of biodiversity loss caused by alien species, as envisioned under
article 8(h) of the Convention on Biological Diversity (CBD).88 In February 2000,
the final guidelines document was published, making the loss of biological diversity
caused by invasive alien species one of the central components of the CBD.89
A July 1996 Conference on Alien Species in Trondheim, Norway, sponsored by
the United Nations Environment Programme, the Secretariat for the Convention on
Biological Diversity (CDB), and the Scientific Committee on Problems of the
Environment (of the International Council of Scientific Unions) provided an
international forum for dialogue among scientists and policymakers on research and
management issues related to alien species. Also in 1996, following concerns being
expressed about the potential ecological harm of certain imported biological control
agents, FAO published the “Code of Conduct for the Import and Release of Exotic
Biological Control Agents.”90 This code was meant to introduce procedures to
regulate imports of biocontrol agents so that benefits are achieved without harming
health or the environment.
In June 1997, the United States submitted a document, Trade in Alien Species,
for consideration at the Tenth Meeting of the Conference of the Parties to the
Convention on International Trade in Endangered Species of Wild Fauna and Flora
(CITES), to further increase international attention to the issue of invasive species.91
In 1998, the FAO published international guidelines for pest eradication. 92 These
guidelines for national plant protection organizations give directions on how to
develop environmentally sound emergency eradication programs.
Finally in 2001, the Global Invasive Species Program (GISP)93 signed a
memorandum of cooperation with the Secretariat of the Convention for Biological
Diversity (CDB) to assist in developing a pilot initiative on invasive species. The
agreement requires that GISP act as an international focal point to disseminate
information on invasive species to Convention Parties, to governments and to the
general public. GISP and the CBD also will collaborate to develop invasive species
Under the North American Free Trade Agreement, a Commission on
Environmental Cooperation (CEC) plays a potentially important role in protecting

88 []. The United States is not a party
to the Convention and its participation is limited to that of an observer state.
89 []
90 []
91 []
92 []
93 The Global Invasive Species Program (GISP) is an independent and international
organization whose mission is “to conserve biodiversity and to sustain human livelihoods
by minimizing the spread and impact of invasive alien species.” (See
[http://j sp].)

native biota. For example, Ontario withdrew permission for Lake Huron cage culture
of exotic Arctic char after the CEC expressed concern. In addition, the CEC wrote
to the United States and Canada in 1988 expressing concern for the potential spread
of exotic ruffe, resulting in new ballast guidelines by Canada (1989) and regulations
by the United States (under NANPCA in 1990).

Coverage of Laws or Policy:
Actions and Approaches
Comprehensive legislation on the treatment of non-native species has never
been enacted, and no single law provides coordination among federal agencies. In

1993, the Office of Technology Assessment found:

The current Federal framework is a largely uncoordinated patchwork of laws,
regulations, policies, and programs. Some focus on narrowly drawn problems.
Many others peripherally address [nonindigenous species]. In general, present94
Federal efforts only partially match the problems at hand.
In the intervening decade, NISC has taken substantial steps toward sharing more
information across governments and with the public. It has also begun to coordinate
actions of federal agencies, asking specific agencies to take the lead in developing
policies within their existing legislative mandates. Through its 2001 report, Meeting
the Invasive Species Challenge, it has also outlined a set of actions (some planned
and a few completed) to address the bulk of existing problems. These actions include
developing legislative proposals to fill gaps in current law. To date, legislative effort
has involved an ad hoc focus on well-established problems: the clear invasion of a
single species, a handful of specific pathways of introduction, or damage or risks to
agriculture. If Congress should choose to regulate non-native species across a range
of species, ecosystems, or pathways, Article I, Section 8 (clause 3) of the
Constitution, with its broad authority to regulate interstate commerce, appears to give
it the authority to do so.
Current laws do not clearly address (a) prevention of biological invasion across
foreseeable pathways (besides ship ballast water); or (b) explicit direction on
management during that critical period between the introduction (or intentional
release) of new non-native species and when the species becomes established and
focus must shift from prevention to control.95 Many scientists assert that the period
shortly after introduction offers one last chance to stop a new harmful non-native
from becoming established. Moreover, there may be economic and ecological
savings from early intervention. For example, the effort to capture a single snake that
might be a brown tree snake newly arrived at an airport in Honolulu, even if it were
to cost tens of thousands of dollars, could prevent the expenditure of millions of
dollars annually to control the snake if it were to become established on Oahu, and
millions more in damage or compensation for losses due to the snake. Congress
could address these gaps either by explicitly delegating such authority to the
President or by crafting legislation.

94 OTA Report, p. 163.
95 The authors in the course of their research discovered very few instances (e.g., smallpox,
nutria in East Anglia, UK) of control measures on a well-established species leading to long-
term eradication. For established species, eradication is extremely improbable. For very
recent arrivals, it could be possible. In contrast, prevention (here including a reduction in
the number of non-natives establishing breeding populations each year) is probably more

Under current approaches, species are selected for control primarily based on
the record of damage they have already inflicted, rather than for preventing damage
that may occur in the future. Since predicting which species may produce
catastrophic effects is difficult (see Predicting an Invasion, above), some agencies
have, or are moving to, a “pathways of invasion” approach, sometimes with the
support or direction of specific legislation (e.g., for ballast water exchange). There
appear to be no current efforts to identify additional likely pathways of invasion,
however. (See Approaches to Regulation: Species-by-Species vs. Pathways, below.)
Also, little emphasis has been placed on preventing the export of native species from
the United States to other countries where they are not native (see Box, p. 6), even
though President Carter’s 1977 Executive Order instructed federal agencies to use
their existing authorities to do so.
President Clinton’s Executive Order 13112 on invasive species (see description,
above) was a step toward a more comprehensive approach. Ultimately, it could lead
to greater agency attention to non-native species (its stated purpose) and to greater
coordination among agencies.96 However, coordination of current efforts alone
means that, where current efforts have gaps due to lack of coverage by existing laws
or agency jurisdiction, those gaps will remain. The 1999 Executive Order directed
agencies to consider the impact of introduced species abroad, but it did not prohibit
exports of species not native to the receiving country.
The Order also created the National Invasive Species Council. Subsequently,
the NISC has brought about major improvements in information-sharing among
federal agencies and with state, local, and private officials. Among other things,
federal agencies, working with the NISC, have met to examine invasive species
problems in light of their existing authorities, and sought to allocate their efforts to
those areas (geographic and topical) that are not handled by other agencies.
Federal Agency Actions: A Patchwork
The NISC has become the federal focus for efforts to control and prevent non-
native species affecting a broad range of industries or ecosystems. However, many
of the shortages of personnel which hampered efforts to limit the entrance of and
damage from non-native harmful species remain.
Some agencies have particularly focused on this problem: the agriculture-
forestry sector is the clear focus of APHIS, and the Army Corps of Engineers has led
the control of non-native aquatic plants. APHIS can regulate imports of plants or
animals that are listed as agricultural threats to this country, but its authority to

96 History did not provide grounds for optimism that the new Order would be implemented
effectively: the OTA Report noted (p. 166) that the 1977 order “in practice ... has been
ignored by most Federal agencies. Moreover, the Fish and Wildlife Service has yet [15
years later] to implement the order in regulations although specifically directed to do so.”
Opposition to proposed FWS regulations came primarily from agriculture, zoos, game
ranches, aquaculture, and the pet trade. A revised version was opposed strongly by the
hobby fish industry. The OTA Report also notes that at that time no major industry
supported the proposed FWS regulations. However, the early years of the NISC suggest that
this pattern may have changed substantially.

regulate living plants or animals once they are admitted is more limited. Most
significantly, it does not regulate the release of species into the wild once they have
been admitted, unless the species is already designated a noxious weed or disease
carrier. It can, for example, inspect imported emus or ostriches for the sake of
protecting domestic poultry from foreign diseases. But after the markets for these
birds crashed some years ago, and many were released by emu ranchers, APHIS did
not have authority to control release of this non-native species.97
Neither does APHIS regulate the commercial sale of species that are already
well-established. Purple loosestrife, Norway maple, and English ivy continue to be
widely sold in commercial nurseries. Even though all are important pests, their sale
does not violate federal law. (See discussion of purple loosestrife in the Gallery
below, for example.) The sale of some of these plants is forbidden by some states,
but the plant could be purchased legally in one state and then moved along with
household effects to another, thereby obviating the protection of the second state’s
laws.98 While these species spread naturally, their sale in nurseries offers new
opportunities to introduce such species in entirely new areas where they are not
currently found, even as expensive control efforts occur in other parts of their ranges.
The Army Corps of Engineers attempts to control noxious aquatic plant species
(e.g., hydrilla) and other impediments to inland navigation. Yet the Corps has no role
in preventing or regulating the release of such pests in the first place. Hydrilla
infestations in Florida and the Potomac River, for example, were very likely caused
by aquarium hobbyists dumping fish tank contents. It is unclear whether the dumpers
violated any state or federal laws, even though their acts have resulted in hundreds
of millions of dollars of private and taxpayer costs. (See Hydrilla, below.) While the
noxious aquatic plant program has been active in the past, it has been reduced
somewhat in a shift in the balance from federal to greater local responsibilities for
maintenance and operation costs.
In contrast, FWS does not have authority to provide general protection for the
country’s ecosystems, nor even to protect those species popular for hunters and
anglers. It could not stop an African game fish, for instance, from being released in
the bayous of Louisiana or the mountain streams of Wyoming on the presumption
that it would unbalance local ecosystems if the fish were to spread. Only if FWS
knew that the species might harm a species protected under ESA would it have clear
authority to stop the importation and release. Similarly, if there were an effort to
import a new grass to improve forage on National Grasslands, it is unclear whether
FWS could prevent the release of the species on general ecological grounds. NMFS
has even less regulatory authority, since its responsibilities for inland waters are
limited, and largely confined to demonstrable effects on anadromous species

97 If they reach pest levels, the Wildlife Services program within APHIS can take steps to
control pest populations.
98 There is a parallel with the state waterfowl hunting laws in the early 20th Century. States
with restrictive, conservation-oriented laws were literally out-gunned by states with more
permissive laws when the waterfowl migrated through several states. Pressure from state
governments (and their hunters) seeking to put all states on an equal footing in the burden
of conservation was a significant factor leading to federal migratory bird hunting laws.

protected under ESA. Without clear federal legal authority to protect the nation’s
ecosystems (except in agriculture), the information sharing under NISC takes on even
greater importance, since simply informing responsible parties of the risks of their
proposed actions may be one of the few vehicles available to deter potentially
damaging releases.
Interaction of State and Federal Programs
The NISC has begun to step into the role of coordinator for federal-state
responses to non-native species.99 At the same time, states do not appear to have a
role in carrying out many of the federal laws to prevent the invasion of harmful non-
native species. For instance, under the Alien Species Prevention and Enforcement
Act, which makes it illegal to ship several categories of species through the U.S.
mail, a state role seems improbable. Nonetheless, within some well-defined arenas,
substantial cooperation does exist. Federal and state cooperation seems to be
especially strong in control of invasive plants where they threaten agriculture or
forestry. APHIS is the lead federal agency for this effort. The Forest Service takes
the lead in working with state, local, and private organizations to control tree pests,
and the Natural Resources Conservation Service (NRCS) works directly with private
landowners to control invasive plants (native or non-native). Some of the
cooperation on federal lands is carried out through National Public Lands Day, an
event coordinated by the National Environmental Education and Training
Foundation, a non-profit foundation chartered by Congress in 1990. Events in 2002
include removal of exotic grasses at Saguaro National Park (AZ), and exotic seaweed
eradication (Gracilaria salicornia) off the coast of Waikiki (HI).
The information-sharing promoted through the NISC may help states to play a
greater role by promoting broader awareness of the potential effects of such species
(thereby limiting plans for deliberate introductions) or by providing states with new
information about strategies to control pests within their borders. Federal agencies
are also more aware of options and techniques to control pests that lie on both sides
of federal boundaries. Some examples of such cooperation include sea lamprey
control in the Great Lakes, and the NPS Exotic Plant Management Teams, which
work closely with neighboring landowners.
Approaches to Regulation: Species-by-Species vs. Pathways
Under a single species approach, plants or animals must be placed on a black
list before they are regulated as harmful. Black list approaches to invasive species
are, of necessity, done on a species-by-species basis. Harm can rarely be
demonstrated unless the plant or animal is already at pest levels and inflicting
damage somewhere, i.e., generally after the species is reproducing and spreading.
Usually, damage must be readily apparent before protection can begin, at which point
prevention could be nearly impossible. Several examples of this approach are extant
in law: coverage of the brown tree snake under NANPCA (which otherwise regulates
the pathway of ship ballast water), and the requirement that individual weed species

99 However, a good deal of information on aquatic nuisance species was already collected
by the ANS Task Force which preceded the NISC.

be placed on an exclusion list before they can be regulated under the Plant Protection
There are a few instances of regulation and prevention by pathway. Among the
most comprehensive has been NANPCA, as amended by NISA. Its focus is on
ballast water as a risk to saltwater and freshwater ports, bays, and estuaries. Its goals
put prevention on an equal or higher footing with control of species that are already
established. It requires the participation of several federal agencies, promotes
research, and implements regulations on the mid-ocean exchange of ballast water and
various other measures to prevent non-natives from entering U.S. ports. Similarly,
APHIS inspects imported agricultural products for pests. Pathway approaches also
exist at the state level. Minnesota, for example, prohibits the transport of nearly all
aquatic plants (native or non-native) and of zebra mussels on public roads.
Depending on the particular offense, fines range from $50 to $500.100 Pathway
approaches do not require lists of organisms to be implemented or effective, and may
even block the entry of species whose very existence is unknown to science.
A Few Legislative or Policy Options
Specialists in this field suggest that the following areas are either not addressed
in current law, or might be explored by policymakers101:
!Research to identify pathways and to improve control methods. A
pathways approach, to ensure that pathways are clean of living
stowaways (regardless of whatever policy regarding black or white
lists may be adopted for intentional introductions), could have some
advantages. Stowaways, per se, have no supporters; opposition to
preventive action would probably be based on practical
considerations of cost, efficacy, safety, intrusion on otherwise legal
goals, etc. However, with the exception of agricultural threats, there
have been few comprehensive reviews to identify pathways
providing the greatest risk of harmful non-natives. This research
could be especially relevant to preventing unintentional
introductions. The research goals would overlap strongly with
research to prevent certain kinds of terrorist threats, and might
benefit from cooperation with agencies involved in anti-terrorism
!Education campaign. After a disastrous human-caused fire in New
Mexico, a young black bear cub survivor was named “Smokey” by
the Forest Service, and became in only a few years the nucleus of a
highly successful educational campaign to reduce similar fires. A
“Smokey Bear” equivalent for non-native species — an educational
campaign, aimed in part at children – to prevent simple, inadvertent

100 Personal communication with Jay Randall, Coordinator, Exotic Species Program,
Minnesota Division of Fish and Wildlife, on May 17 and July 14, 1999.
101 Congress is considering many issues related to invasive species. The list of options
below focuses only on topics which cover a broad range of species, pathways, or agencies.

acts by the public might play a significant role in preventing some
types of non-native species introductions.102 Preventing releases of
exotic pets and aquarium species after the point of sale might be
particularly susceptible to this approach.
!Warning list. While the current “black list” approach requires
significant regulatory hurdles before a species can be included, an
informational warning list (or “grey list”) of species might be
created by the collaboration of federal and state agencies. The
warning list might include species currently restricted under state
laws, species thought to be newly arrived from other countries, and
other species felt to merit special attention by regulators.103
Although it would lack regulatory force, the list could be designed
to provide information on species whose eradication or control is in
its early phases. Unification of data and reporting from many
agencies would add greatly to the utility of such a list.
!Review of industries dependent on importing and transferring non-
native species. Such a review, including a focus on cooperative
methods to reduce introductions or releases after the point of sale,
could be in order. The focus of past efforts has tended to be on the
point at which these species enter the United States. To protect their
businesses, import-dependent industries have naturally tried to
reduce current obstacles and prevent imposition of new ones. In this
effort, the pet trade (including the hobby aquarium and nursery
industries) has been relatively successful. Yet this pathway offers
other avenues to reduce risk besides prohibition. These avenues
might include incentives for the sale of sterile animals or plants only
or efforts to create point of sale educational programs to inform
purchasers about the risk of releasing pets or plants into the wild and
penalties for doing so. The Wild Bird Act (see above) could provide
a model for legislation to encourage “homegrown” (if not native)
species over additional foreign imports.
!Multi-agency federal center for “first strike” prevention and
control. Since the creation of the NISC, agencies have begun to
respond across a broad front in the days, weeks, or months after an
invasion is discovered. The prompt notification and agency

102 While Smokey Bear has become widely recognized, other such efforts have been less
successful. For example, the Forest Service’s other symbol, Woodsey Owl, has been far less
effective in reducing pollution and littering. In the early 1960s, USDA attempted to create
“Pestina” to help educate the traveling public to the perils of non-native species imports.
There was little effort to evaluate effectiveness, and little work with private and other
federal agencies. The program was eventually dropped. (OTA Report, p. 142.)
103 Appendix III of the Convention on International Trade in Endangered Species could
provide a model for this type of approach. A nation may list any species native to it under
this Appendix; through that listing, it requests the assistance of other member nations in
controlling imports of that species when they arrive from the host nation.

attention to the discovery of northern snakeheads in Maryland is an
example of such a response. (See Snakeheads, below.) However,
while constraints on time, budgets, coordination, and jurisdiction
interfere with prompt responses far less than in the past, further
progress is possible. NISC is moving toward the model of a federal
program which has long faced similar issues: interagency fire
management.104 It seems possible that a similar, multi-agency
federal center devoted to “first strike” prevention and control of
harmful non-native species, regardless of affected industry,
ecosystem, or lead agency could be helpful. With a variety of
expertise and resources, it could provide critical support at a time
when eradication might still be possible. Another federal agency
which plays a somewhat similar role is the Centers for Disease
Control and Prevention, which conducts research and provides a
degree of coordination for efforts to protect human health.105
In recent years, one agency (NPS), has adopted roughly this
approach, within their budget constraints. Initially two teams were
available to address invasive plant problems, not only in crises, but
also for ongoing problems. While the teams (soon to number 16) can
work only on NPS lands, they do work with adjoining landowners to
control cross-boundary problems. Expansion of this program,
perhaps with multi-agency teams, could provide a more efficient
method of addressing new or incipient invasions. It seems unlikely,
however, that each federal agency would need to create its own
separate team modeled after those of NPS, since the duplication of
effort would be substantial.
!Expert review of planned releases. Panels of experts might be
created to review and make recommendations on releases by
governments at any level, or by non-governmental sources into any
environment in which the species are not native. According to the
NISC,106 steps along these lines are planned, and in the case of plants
which may affect agriculture, are in progress. While such a panel
could not have sounded the alarm on the unauthorized release of
hydrilla into the Potomac, for instance, it could provide a public
warning on a planned release of exotic grasses by federal agencies
or of a non-native game fish species into a new drainage. The use
of the expertise of federal and other scientists and managers, if it
prevented even a few ill-advised introductions, might be a cost-
effective option.

104 These issues are addressed by a federally coordinated National Interagency Fire Center,
primarily under the management of the Bureau of Land Management. All federal land
managing agencies participate, and a great deal of the program focuses on work with tribal,
state, and local governments to bring many resources to bear on major fires.
105 For more on the National Interagency Fire Center, see []. For more
on the Centers for Disease Prevention and Control, see [].
106 Meeting the Invasive Species Challenge, p. 32-33.

!Measures to reduce the risk of exporting invasive species. Even in
the absence of a treaty, the United States might wish to take internal
steps to prevent exporting potentially invasive species to other
countries. These measures could be as simple as restricting their use
in bilateral aid programs or certifying that identified U.S. products
(e.g., used tires) are free of pests. This certification, for example, is
done for agricultural shipments, but other areas or programs may be
at risk of transporting non-natives as well. The management plan of
the NISC considers international cooperation generally (p. 41-42)
and describes actions which might be taken on a multilateral or
bilateral basis to reduce the transport of invasive species. However,
it does not address steps the United States might take unilaterally,
nor assess any positive or negative results on U.S. trade that might
occur from such steps. It is difficult to discern progress in this area
in the last few years.
!Convening an international conference. To prevent further
economic damage and enlist international cooperation, Congress
might consider urging the President to seek an international
conference to develop a treaty or other international agreements
concerning this issue. Certification of the pest-free status of plant or
animal specimens, pallet wood, or air cargo holds, or the adoption
of other measures, might reduce the number of species entering this
country, as well as prevent threatened trade wars if steps are taken
unilaterally in the face of a new pest. Such protocols might have
been helpful in U.S.-China discussions over the Asian longhorned
beetle, for example.

A Gallery of Harmful Non-Native Plants and Animals
Below is a discussion of selected harmful non-native species, with emphasis on
their economic impacts (where known), the affected industries or interests, the origin
of the species, its pathway into this country, and its effects on natural ecosystems.
Species are selected on the basis of past congressional interest, amount of economic
damage, availability of information, and ability to illustrate the range of problems
associated with introductions of non-natives. (Beneficial non-natives are not
included; some species are included that are native to some regions of the United
States but have become invasive in areas where they are not native.) Comparatively
recent arrivals are emphasized over long-term non-natives. Most are well-
established, but a few are not. Species are grouped by taxonomic affinities:
microorganisms, plants, insects, other arthropods, mollusks, and vertebrates.
Whirling Disease, Myxobolus cerebralis. Whirling disease is a
protozoan parasite that affects the nervous system of trout species. This parasite must
pass through two hosts in its life cycle — fish and a common aquatic worm. A free-
swimming stage enters young trout where it attacks their cartilage. This parasite was
first introduced to the United States from Europe in the 1950s, probably in infected
trout. The disease spread as these infected trout were distributed among hatcheries
or were stocked in open waters. According to information obtained by querying the
database for the National Wild Fish Health Survey []
on November 13, 2002, this disease has been detected in rainbow trout in at least 32
states and now occurs in wild rainbow trout in at least 23 of these states. (In the
remaining states, this disease is believed to be confined to fish hatcheries.) While
whirling disease is not a major problem in eastern states, it is severe in some western
states, and has ravaged trout populations. To date, severe damage has been primarily
to wild rainbow trout, although other salmonid species can become infected.
Although several states are spending tens of millions of dollars annually to control
whirling disease, no national or international cost estimates were found for damage
caused by this species. In the 104th Congress, Sen. Baucus introduced S.1019, to
direct FWS to examine the impacts of whirling disease, and other parasites and
pathogens, on trout in the Madison River, and similar natural habitats. No action was
taken on this measure, and no additional bills specifically addressing whirling disease
have been introduced since the 104th Congress. Beginning in FY1997, federal
funding specifically for combating whirling disease has been provided in the
Department of the Interior appropriations for FWS. For more information, see:
[ h ttp:// irling/ centerpage/whirling.html] ;
[]; and [].
All of the plants described in this report are covered in the comprehensive
FICMNEW report (cited above). It analyzes 20 major invasive plant species, as well
as their effects on different habitat types. Substantial information, particularly on the
history of the plant invasions cited below, was drawn from the FICMNEW report.

Leafy Spurge, Euphorbia esula. This aggressive invader, native to
Eurasia, was brought to this country in 1827 (and again at several later dates),
possibly in contaminated seed. It is now found throughout the contiguous United
States, except in the southeast. In open areas of pasture or rangeland, it crowds out
other vegetation, and at concentrations above 10-20% cattle will not graze in infested
land because of the irritating nature of the chemicals contained in the plant. The
federal role has included USDA research on biological and chemical control methods
and estimates of economic impacts. Biological control is being used in many areas,
and USDA has shown success using several natural enemies of leafy spurge imported
from Europe. States have their own major control programs, some funded by a cost-
sharing program among states, local governments, and landowners. Direct and
indirect economic effects of this species alone are estimated at hundreds of millions107
of dollars. According to USDA, damage costs ranchers an estimated $35-45
million per year.
Purple Loosestrife, Lythrum salicaria. This wetland invader was
imported from Europe in the early 1800s for its medicinal value, and for the beautiful
purple spikes of the blooming plant. Unsuspecting visitors to an infested wetland
often admire the beauty of the marsh when L. salicaria is in bloom, unaware that it
has crowded out native plants and animals. This species is still sold as an ornamental
in nurseries in some states, though many states have listed it as a noxious weed and
prohibit its sale. According to FWS, purple loosestrife now occurs in every state
except Florida. The plant is virtually impossible to eradicate, and its vegetative
dominance may increase the likelihood of listing additional native species as
threatened or endangered. One mature plant is capable of producing 2.7 million
seeds in one season. Intensive chemical and mechanical control measures to reduce
stands have been used for some time. Emerging biological control approaches show
promise for improved control in the future, according to scientists. Estimated
economic impacts are $45 million per year in forage losses and control costs.108
Spotted, Diffuse, and Russian Knapweed, Centaurea maculosa, C.
diffusa, Acroptilum repens, and Yellow Starthistle, Centaurea
solstitialis. The knapweeds were introduced from Eurasia as contaminants of
alfalfa and clover seed, and one or the other of them is present in every state but
Alaska. They are particularly problematic on rangelands in the western United
States, because they are highly unpalatable to livestock and deleterious to wildlife
habitat. According to reports, in Montana alone it is estimated that knapweed
infestations cost $42 million in livestock productivity losses and control costs.
The yellow starthistle, a native of southeastern Europe, was introduced in the
early 1850s apparently as a contaminant in alfalfa seed from South America. The
flowers have stiff spines that can injure humans or livestock; they may grow in such
dense stands as to prevent foot travel. The weed is also poisonous to horses. It is
found in much of the west, primarily in rangelands but also in alfalfa and cereal grain
croplands, orchards, vineyards, roadsides, and recreational lands. It is still spread via
contaminated seed and it appears that recreational vehicles are a newer means of

107 FICMNEW, p. 26-28.
108 Pimentel, et al.

transport. The species is most common in California, where it infests an estimated
10-15 million acres; and in Idaho it infests well over 1 million acres. Economic
impacts are unknown, but native vegetation is crowded out where the plant is
common. Treatment consists of application of herbicides to infested areas.
Melaleuca, Melaleuca quinquenervia. This Australian tree was
introduced in the early 1900s as an ornamental. It is established in Florida,
Louisiana, Hawaii and Puerto Rico, and is virtually at epidemic levels in Florida. In
Florida, it was originally used as a windbreak and soil stabilizer, but it is also a heavy
water user. In 1936, a private individual wishing to drain the Everglades spread
seeds via airplane through southern Florida. It has had a major influence on water
management throughout the area. It has a camphor-like odor, and its flowers and
young leaves can cause skin and respiratory reactions in some people. Destruction
of native vegetation, e.g., by hurricanes, opens up further areas for Melaleuca
infestations. Its spread is complicating efforts to restore the Everglades and improve
water supplies in the economically growing area.
Water Hyacinth, Eichhornia crassipes. This freshwater aquatic plant
originally came from South America, and forms impenetrable mats of floating
vegetation (as much as 200 tons per acre). It was believed to have been introduced
to the United States at the World’s Industrial and Cotton Centennial Exposition in
Louisiana in 1884-1885, after which a Florida visitor returned home and released the
plant into the St. Johns River, east of Orlando. Currently its range includes Hawaii,
California and most southern states, but scattered sightings have been reported as far
north as Cape Cod. Water hyacinths clog flood-control and irrigation systems,
provide habitat for disease-carrying insects such as mosquitoes, and prevent boats
from moving on waterways. They also drastically reduce the diversity of native
aquatic species, lower dissolved oxygen levels in the water so that fish die, accelerate
the rate at which bodies of water fill in with silt, and prevent fish from spawning by
covering spawning beds. U.S. annual expenditures to control aquatic weeds (most
of them non-natives, such as water hyacinth) are reported to be $100 million.109 For
more information, see [] and
[ h ttp://] .
Salt Cedar, Tamarix (several species). Salt cedar species are spreading
shrubs or small trees native to Eurasia, and were introduced as an ornamental plant
in the United States by nurserymen in the 1830s. Salt cedar is now established in
many moist spots in the desert regions of western states. It is an aggressive colonizer
that is able to survive in a wide variety of habitats, and often forms monotypic stands,
replacing willows, cottonwoods and other native riparian vegetation. Seedlings
establish most frequently in soils that are seasonally saturated at the surface. It
appears to grow best in saline soils (up to 15,000 parts per million sodium), but salt
cedar is adaptable and tolerant of a wide variety of environmental conditions
(Brotherson and Field 1987).
Hydrilla, Hydrilla verticillata. This freshwater aquatic plant originally came
from Asia and has become the most abundant aquatic plant in Florida, where it grows

109 OTA Report, p. 67.

in thick surface mats and displaces native vegetation. This plant was imported into
the United States in the early 1950s for use in aquariums, and was likely discarded
into the wild near Tampa and Miami. A subsequent introduction occurred in the
Potomac River basin. Distribution in the United States now ranges from Connecticut
southward along coastal states to Texas as well as on the west coast in California and
Washington. Several inland states — Pennsylvania, Tennessee, and Arizona — also
have populations in some lakes. Generally, this species is most likely to spread when
plant fragments are carried along with recreational boats into new habitat.
Hydrilla causes major problems with water use. In drainage canals, it greatly
reduces flow, which can result in flooding and damage to canal banks and structures.
In irrigation canals, it impedes flow and clogs intakes of irrigation pumps. In utility
cooling reservoirs, it disrupts flow necessary for adequate water cooling. Hydrilla
can interfere with recreational and commercial vessel navigation. In addition to
interfering with boating by fisherman and water skiers, hydrilla hampers swimming,
displaces native vegetation communities, and can damage sport fish populations.
The economic losses in these water use values to property owners, tourists, and users
can be staggering. U.S. annual expenditures to control aquatic weeds (most of them
non-natives, such as hydrilla) are reported to be $100 million.110 In the 99th Congress,
P.L. 99-662 included a provision directing the Secretary of the Army to study the
feasibility of eradicating and controlling hydrilla in the Potomac River. For more
information, see
[] and
[ seagrant/hydver2.html] .
Cordgrass, Spartina sp.. Although native to the eastern United States, this
plant is considered an invasive marine weed in Washington, Oregon, and California.
It was accidentally introduced to the Pacific Northwest more than 100 years ago,
probably as packing material around oysters that were seeded there. Spartina
radically alters native Pacific intertidal ecosystems, including the food webs, from
mudflats to high marsh. This alteration affects the Pacific Coast’s ecologically and
commercially important native species. In 1995, the Washington Legislature
declared the spread of Spartina to be “an environmental disaster.” The Washington
state government, local agencies, tribes, and non-profit organizations reportedly
spend millions of dollars annually on efforts to eradicate cordgrass. For more
information, see
[] and
[ h ttp:// ~ipmpa/Nox spart.html] .
Caulerpa, Caulerpa taxifolia. Native to tropical oceans, Caulerpa taxifolia
escaped in 1984 from a public aquarium in Monaco and subsequently spread to cover
more than 6,000 hectares of the northwestern Mediterranean Sea, seriously reducing
biodiversity in this area. The algae form a dense, uniform carpet that persists from
year to year, and grow well in many diverse habitats. It is toxic and inedible to fish
and marine invertebrates; it spreads unrestrained, covering and then eliminating many
plant and animal species. The 1999 discovery of Caulerpa on the Californian coast
near San Diego raised public concern about the potential danger of a new invasion

110 OTA Report, p. 67.

similar to the one in the Mediterranean. Substantial efforts are being expended to
eliminate the California invasion.111 For more information, see
[] and
[ h ttp:// w q c b 9 / N e w s /C aulerpa_tax i folia/Fact_sheet_11-01-01.
Arthropods: Insects
Formosan Termite, Coptotermes formosanus. The Formosan
subterranean termite is native to China and east Asia. It is known to have spread to
Sri Lanka, South Africa, Hawaii and the southeastern United States. Its spread
probably began with the return of various tankers and cargo ships after World War
II; returning cargo probably rested on or in infested packing material and pallets. The
major threat posed by this species went unrecognized for more than 20 years,
although a few scientists tried to sound the alarm.112 The species now exists from
California to Florida and north to Virginia, with ideal habitat being found particularly
in the more humid Gulf Coast area. The species does not exist where winters are
more severe. In very dry areas a source of water, such as a leaky pipe, is essential for
their survival. Spread of the colonies appears to be primarily by human transport of
infested wood or soil. (The winged queens and kings are very weak fliers.)
The termites are extremely destructive and colonies eventually have millions of
workers and soldier termites. Severely infested structures will collapse — a stage
that is reached more quickly with this species than with domestic species of termites.
When living trees are infested, treatment is extremely difficult, since pesticides on
the surface of the tree have very little effect on the termites inside. Destruction of
trees in New Orleans is severe, leaving some streets virtually bare. Damage from the
species, plus the cost of treating infected buildings and trees, is estimated in the
hundreds of millions of dollars annually in New Orleans alone, and about $1 billion113
The widespread distribution of this species combined with the severe difficulty
in controlling it means that its major limiting factor may be its relative intolerance
for lower temperatures and lower humidity. Even so, central heating and dense
construction may allow a limited invasion into heated buildings in colder states. The
current focus of the federal government is on treatment and methods of control, more
than on the prevention of new imports of a species that is already widely distributed.
Currently, research into control and detection methods is being conducted by
USDA’s Agricultural Research Service, whose program is described at
[] .

111 Jay Withgott, “California Tries to Rub Out the Monster of the Lagoon,” Science, v. 295
(March 22, 2002): 2201-2202.
112 One of these scientists, Jeffery LaFage, an entomologist from Louisiana State University,
had just begun an effort to support treatment in the historic French Quarter of New Orleans
when he died in 1988. The French Quarter is now probably the most highly infested area
of the Gulf, due to the favorable climate and the architecture of the area.
113 Agricultural Research Service at [].

Imported Fire Ants, Solenopsis invicta and S. richteri. Fire ants first
entered the United States from Argentina through the port of Mobile, Alabama,
perhaps as early as 1918. Since then up to five different species, including the red
and the black imported fire ants, have spread through much of the southeast,
reportedly as far north as Maryland, and west into Southern California. These
species develop very large surface-dwelling colonies in disturbed areas such as
pastures and lawns. The sting of an individual ant is usually severe, and the colony’s
habit of swarming quickly up the leg of any animal that slows briefly near a nest has
earned the species a ferocious reputation. In severe cases or among sensitive
individuals, some (human, cattle, and other species) have died from the stings; even114
rainbow trout have been killed. Some agricultural areas are severely hampered
with high levels of infestation. In residential areas, people complain of being unable
to use their yards, or allow their pets outside. Estimated damage to livestock,
wildlife, and public health in Texas alone are $300 million annually, and $2 billion115th
per year nationally. In the 105 Congress, Sen. Gramm introduced S.932 to
establish a National Advisory and Implementation Board on Imported Fire Ant
Control, Management, and Eradication to provide grants for research or
demonstration projects related to the control, management, and possible eradication
of imported fire ants; the bill was not acted on.
An unrelated ant species, the little red fire ant (Wasmannia auropunctata), was
found in Hawaii in 1999. This tiny reddish invader, a native of tropical America and
from south Florida, is a common inhabitant in orange and coffee groves, and is noted
for its painful and long-lasting sting.
Argentine Ant, Linepithema humile. Argentine ants (until recently called
Iridomyrmex humilis) have been present in the United States for about a century.
These ants are common household pests in most parts of the country, including
Hawaii. Their sting is negligible except to unusually sensitive persons. The ants can
enter very small openings to take food from all but the most tightly sealed containers.
They can be serious garden and orchard pests due to their habit of guarding aphids
and certain other plant pests and feeding off of the honeydew produced by these
insects. The guarded pests thereby reach population levels much more likely to
damage the host plants. In optimum habitats, colonies of Argentine ants can reach
300,000 ants in colonies with multiple queens capable of laying thousands of eggs
per day. They out-compete most other native ant species for food sources. Even that
other major ant invader, the fire ant, may find itself starved out of an area due to the
efficiency of the Argentine ant. In turn, populations of lizards, frogs, and other
organisms that feed on native ants may plummet.
Economic effects fall primarily on horticultural species and commercial crops,
from oleander to oranges. Homeowners are affected as well. To the extent that the
Argentine ant reduces populations of animals (e.g., through competition) or plants

114 “Fire ants to blame for deaths of trout,” by Thaddeus Herrick. Houston Chronicle. June
11, 1998. The trout had attempted to ingest winged queen and male ants that had fallen into
a stream; it is unclear whether the fish were stung by the queen ants (males do not sting) or
whether the toxins in the ants poisoned them.
115 “Deadly southern fire ants are on the move,” USA Today, Dec. 15, 1998, p. 15A.

(e.g., through displacing a plant species’ closely adapted pollinators or allowing plant
pests to increase), the species could cause some species to be listed under the
Endangered Species Act, thereby increasing regulatory burdens on affected parties.
For more information, see
[ hnis/index .html#Li nHumI01].
Africanized Honeybee, Apis mellifera scutellata. This subspecies of
honeybee is an extremely close relative of the European honeybee, familiar to116
beekeepers around the country. Neither subspecies is native to North America but
the European honeybee is one of the arrivals to North America whose benefits in crop
pollination are thought to outweigh the detrimental impact on population levels of
native bee species.117 The sting of both subspecies is equal in severity, and worker
bees of both species die as the result of stinging. Africanized bees are far more likely
to attack, and attack in greater force, than their calmer European sisters. This
reduced threshold for aggression poses dangers for humans, pets, domestic animals,
etc., who may wander unknowingly past a hive, and for commercial beekeepers who
find it far more difficult to manage their hives, and to move them to commercial
orchards for pollination services.
After an accidental escape from research colonies in Brazil in 1957, the
subspecies spread north and reached the U.S. border about 10 years ago. In the
southern United States, a few very serious attacks (including at least four human
deaths) have occurred. Current control efforts have fallen heavily on the beekeeping
industry, which has had to supply new European queens to maintain the stability of
working colonies. The economic impact has been an added blow to beekeepers (and
therefore orchardists) suffering from other serious pests such as bee mites (described
below). In a touch of environmental justice, however, these same bee mites attack
Africanized bees as well as European bees, and the mites may be one reason why
Africanized bees (unprotected in the wild by human keepers) are expanding their
U.S. range somewhat more slowly than expected. The increased costs of control
measures could affect the cost of pollination services, reduce the number of
beekeepers, and ultimately increase food costs for the crops (from alfalfa to oranges)
that require pollination by bees.
Asian Longhorned Beetle, Anoplophora glabripennis. The Asian
longhorned beetle has done much in recent years to increase awareness at the highest

116 The name “killer bee” has been abandoned by most experts because of the hysteria and
panic it induces. Instead, “Africanized bee” is now accepted by entomologists as a name
with a more neutral emphasis on both its geographic origin and successful adaptation to
local conditions. In Europe, honeybees have been kept for millennia; in the process,
beekeepers naturally selected for unusual gentleness. Bee colonies have not been kept in
Africa until relatively recently, and natural selection favored those wild colonies able to
defend themselves most aggressively from attack, leading to a more aggressive subspecies
than European bees.
117 Most native North American bees (e.g., carpenter bees and sweat bees) are solitary, and
many play an important role in pollination of wild plants and some crops (e.g., squashes,
watermelons, and cantaloupes). Where honeybee populations are high, competition can
reduce populations of native bees; where mites have reduced populations of honey bees,
native bees are increasing.

levels of government of the threats posed by the introduction of non-native species.
This species has been reported in New York state and the area around Chicago. It
appears to have arrived in packing materials or pallet wood from China, but the
beetle is also native to Japan and Korea. It is considered an important threat to trees
in its native range, and an even more serious threat elsewhere. In China, it attacks
elms, poplars, and willows, among other species. In this country, it attacks a broad
range of species, including willow, poplar, birch, rose of Sharon, horsechestnut, most
maple (Acer) species (red, sugar, silver, box elder, and sycamore maples, as well as
the introduced Norway maple), and many others. The species spreads slowly, and
may infest a tree for years before the weakened tree dies. Because the larvae live
deep within the tree, treating the living tree by spraying pesticides on its bark is
usually ineffective. Cutting infested trees or treating them with systemic insecticides
(i.e., injected into living wood) are currently the only practical treatments.
In response to the threat posed by these beetles, APHIS issued an emergency
regulation (7 CFR 319.40) prohibiting imports of untreated solid wood packing
material from China. The regulation became effective Dec. 17, 1998. It requires
solid wood packing material from China to be treated in any of several specified
methods (including fumigation with methyl bromide) to kill this and other pests, and
requires shipments from China to pay an inspection fee to cover the costs of these
services. Other countries in eastern Asia also harbor this beetle, but were not
included under the regulation. These regulations will reduce the chance of importing
other species of pests from China that may inhabit solid wood. Since treatment will
increase costs to export Chinese products to the United States, China objected to the
regulation and threatened a trade war. Environmentalists also objected to the
inclusion of fumigation with methyl bromide (a contributor to atmospheric ozone
depletion) as an acceptable treatment option. Many observers cite this controversy
as contributing to much greater attention at higher levels of government to problems
created by the proliferation of non-native species. (For more information see
[ .html] .
In August 2001, a closely related species, the citrus longhorned beetle
(Anoplophora chinensis), was detected in a tree nursery in King County,
Washington. According to USDA, the beetles were introduced inside bonsai trees
from Korea, and some adult beetles were seen escaping into the environment. Like
the Asian longhorned beetle, this species can attack a variety of hardwoods, including
citrus trees. Washington state has placed a plant quarantine on all properties around
the nursery, and has ordered the destruction of over 1,000 trees. At present, it is not
known if the pest has become established. Another relative, the white-spotted citrus
longhorned beetle (Anoplophora malasiaca), was intercepted in Wisconsin in 1999
in bonsai maples from Asia. No further reports on the status of this pest are
Asian Tiger Mosquito, Aedes albopictus. This mosquito is thought to
have arrived to Houston, Texas, in 1985, in tires imported from Asia for re-treading.
Its larvae are able to survive in almost any amount of standing water, from backyard
dog dishes to cemetery flower pots. Unlike most mosquitoes, this one is diurnal,
making it more likely than other mosquitoes to bite (largely diurnal) humans. The
species can carry West Nile fever, encephalitis, dengue hemorrhagic fever, yellow
fever, and several other important diseases. The tiger mosquito may also be able to

transmit canine heartworm. The Centers for Disease Control and Prevention (CDC)
initially was concerned that the species could spread epidemics, but to date, no major
epidemics have occurred. This prolific breeder has reportedly made some areas of
the south-central and Gulf Coast states very unpleasant when its populations reach
their highest densities.
Economic impacts have included higher costs for mosquito control programs
in humid areas. Its possible medical threat is a more complex question. Its apparent
failure to spread diseases so far has probably resulted from the complex biological
interaction of the viruses, the mosquitoes, and the hosts. The insect’s broad range of
meal sources reduces the probability of transmitting most diseases: if it picks up
yellow fever, for example, it will not transmit it to a human if its next meal is mouse
blood. And a female mosquito may bite only a handful of times in her short adult
life. In another odd twist, it may be that the larvae of this mosquito are out-
competing the larvae of an introduced closely-related and dangerous cousin, Aedes
aegypti, a very efficient transmitter of yellow fever. The CDC, responding to the
public health threat, took steps to require the disinfection of imported tires. No
disinfection of exported tires is required. As a public health matter, this disparity is
unfortunate, since difficult sanitation conditions and reduced health care make the
transmission of disease by this species far more likely in other countries than in the
United States.
Mediterranean Fruit fly, Ceratitis capitata. The Mediterranean fruit fly,
or medfly, is one of the world’s most feared plant pests because the species has a
wide range of host plants, and its larvae destroy many kinds of fruit and vegetables.
Medflies attack over 260 host fruits and vegetables, and their maggot-like larvae
destroy fruits or vegetables before becoming flies themselves, and beginning the
process again. The species originated in sub-Saharan Africa but has spread to several
countries in Europe and Central America. Medfly is not currently known to be
established anywhere in the continental United States. The first known U.S.
mainland infestation occurred in Florida in 1929, with several infestations since,
especially in that state and in California. All these infestations were eradicated with118
the use of pesticide sprays, and more recently with the use of sterile males.
Unfortunately, medflies have been present in Hawaii since 1910, and all eradication
efforts over the decades there have been unsuccessful.
Detection of medflies by U.S. or foreign plant health quarantine authorities
generally results in an automatic ban of all fruit and vegetable trade from that
country. For example, live medfly larvae were recently found in ‘clementine’
oranges from Spain in North Carolina, California, Louisiana and Maryland. In
response, the Secretary of Agriculture immediately banned clementine shipments
from Spain. These severe production and trade implications are the main reason why
USDA maintains extensive fruit fly monitoring and eradication programs in several
states and territories.

118 USDA maintains medfly rearing facilities abroad which produce sterile males for
shipment to the United States as needed. Upon detection of a medfly hotspot in the United
States, millions of these sterile flies are flown in from these facilities and released.

Other Arthropods
Honeybee Mites, Acarapis woodi and Varroa jacobsoni. The
honeybee, itself a non-native species, has been threatened not only by its Africanized
relative (see above), but also by two invading bee parasites. These mites (not insects,
but tiny eight-legged relatives of spiders) are the tracheal mite (A. woodi) and the
varroa mite (V. jacobsoni) from Europe and Asia, respectively. Tracheal mites clog
the air passages of adult honeybees, eventually suffocating them. Varroa mites suck
blood from adult and juvenile honeybees. Adults can be weakened to the point of
death, and juveniles emerge deformed from their cells. Moderate infestations reduce
pollination services and honey production, and eventually kill colonies. Costs of119
keeping bees escalate, increasing crop production costs and food prices. Hobby
beekeepers are virtually eliminated, as are wild populations of honeybees. The
spread of these two kinds of mites may be playing a role in slowing the spread of
Africanized bees farther from the Mexican border, since they too are susceptible to
these mites. Populations of native bees (mostly solitary species such as carpenter
bees, sweat bees, leaf-cutter bees, and others, plus some social species such as
bumble bees) are increasing as the mites decrease the number of honeybees (of
whatever subspecies) competing for available pollen.
Commercial orchardists have relied on movable commercial beehives, to have
their crop and eat it too: while bees are present and working the crop, no pesticides
are used, but when pollination is finished, commercial hives are easily removed, and
crops can be sprayed to protect them from insect pests, blights, etc. Consequently,
while the home gardener may be able to rely on increasing populations of native bees
to take up the slack if wild honeybee colonies are declining, this option is more
difficult for commercial growers. USDA researchers are seeking to control these
mites in a number of ways: resistant strains of honeybees from areas where these
parasites originated, changes in hive management, use of special foods to create
greasy bees that are unattractive to mites, and chemical methods. Congressional
issues have included primarily funding for research on control methods. For more
information about varroa mites and tracheal mites, see
[], and
[], respectively.
European Green Crab, Carcinus maenas. This species was introduced
to the U.S. Atlantic Coast from Europe’s North and Baltic Seas more than 150 years
ago. Around 1989, this very aggressive crab was introduced into San Francisco Bay
where it feeds on bivalve mollusks and competes with native shore crabs. The
European green crab also has a reputation for consuming large numbers of juvenile
clams and oysters. On the Pacific Coast, it is extending its range northwards —
mature adults have been caught as far north as the west coast of Vancouver Island,

119 Although crops pollinated by honeybees are valued at about $10 billion annually,
pollination services represent only a very small fraction of the cost of producing most crops.
Shortages of hives will have to become severe to have substantial effects in supermarkets.
In the meantime, the beekeeping industry itself suffers most.

British Columbia. The annual estimated economic damage to shellfish production
of the European green crab is about $44 million.120 For more information, see:
[ h ttp://] ,
[], and
[ h ttp:// sn_arc98/6_13_98/fob2.htm] .
Chinese Mitten Crab, Eriocheir sinensis. This native of mainland China
and coastal areas along the Yellow Sea was first collected in South San Francisco
Bay by a shrimper during the winter of 1993. Although mitten crabs had previously
been found elsewhere in the United States, San Francisco Bay was the first place
where this crab could feasibly reproduce and increase its numbers. This crab spends
90% of its life in freshwater, migrating to saltwater to reproduce and die. Mitten
crabs are omnivorous, with juveniles eating mainly vegetation. Some are concerned
that burrows excavated by these crabs could accelerate bank erosion and cause levee
damage in the Sacramento River delta. Although this crab is known to be the
intermediate host of the Oriental lung fluke that can cause often fatal, tuberculosis-
like symptoms in humans who consume these crabs raw or poorly cooked, this
parasite has, thus far, not been found in the United States. At the height of their fall
migration to saltwater in 1998, as many as 30,000 downstream-migrating adult mitten
crabs clogged the fish salvage and trash screens at the Tracy (CA) irrigation pumps
every day. The California Department of Fish and Game has rejected a petition to
allow a test commercial fishery for these crabs, which are illegal to possess or
transport live under current state law. While some are concerned that crabs could be
intentionally transplanted to other rivers in an attempt to create a fishery, others
believe a properly managed mitten crab fishery could be an economically viable way
to help control this species. Meanwhile, a closely related Japanese mitten crab (E.
japonica) has been found in the Columbia River Basin. For more information, see:
[ h ttp://www.wsg. washingt reach/mas/nis/mittencrab.html]
[], and
[ h ttp:// /mittencrab/index .html] .
Rusty Crayfish, Orconectes rusticus. This native to streams in the Ohio,
Kentucky, and Tennessee region has been spread widely into adjacent states by
anglers who use them as bait. Rusty crayfish are prolific and can severely reduce
lake and stream vegetation, depriving native fish and their prey of cover and food,
and reducing food for fish and waterfowl used to dining on smaller native crayfish.
The decline of native crayfish species could harm entire aquatic ecosystems, since
native crawfish are a favorite meal of bass, sunfish, and other predators. These
predators are also important sport fish. It is unclear, however, whether these
predators could substitute rusty crayfish for native crayfish species. For more
information, see
[ h ttp://] ,
[], and
[ h ttp:// .gov/crustaceans/maps/or_rusticus.gif] .

120 K.D. Lafferty and A.M. Kuris. “Biological Control of Marine Pests.” Ecology, v. 77, no.

7 (1996): 1989-2000.

Spiny Water Flea, Bythotrephes cederstroemi. This native of Great
Britain and northern Europe (east to the Caspian Sea) was first found in Lake Huron
in 1984, probably imported in the ballast water of a transoceanic freighter. Currently,
the animal can be found throughout the Great Lakes and in some inland lakes where
it competes with young perch and other small fish for food. This species is easily
spread when eggs and adults are transported in bilge water, bait buckets, and
livewells. Also, fishing lines and downriggers can become coated with both eggs and
adults. For more information, see
[] and
[ hotrephes/fs-049.html] .
Zebra Mussel, Dreissena polymorpha. In the late-1980s, zebra mussels
were discovered in Lake St. Clair, between Lake Huron and Lake Erie, having arrived
from eastern Europe via ballast water discharge from European freighters. This
species spread rapidly to 20 states and as far as the mouth of the Mississippi River.
Although early estimates of U.S. expenditures to control zebra mussels and clean
water intake pipes, water filtration equipment, and electric generating plants and
other damage were $3.1 billion over 10 years, recent reports suggest these 10-year
costs were more likely between $750 million and $1 billion. In addition, others are
concerned about potential damage to Pacific salmon freshwater spawning habitat if
zebra mussels spread to Pacific Coast drainages. The 100th Meridian Initiative, a
cooperative effort between state, provincial, and federal agencies, seeks to prevent
the westward spread of zebra mussels and other aquatic nuisance species in North
America. On the other hand, filter-feeding by this mussel has greatly improved water
clarity in the Great Lakes. For more information, see
CRS Report 90-116 ENR, The European Zebra Mussel, Dreissena polymorpha,
[], and
[ h ttp:// ebra.html] .
Brown Mussel, Perna perna. A native of Brazil, Venezuela, and South
Africa, this species was introduced into the coastal waters of Texas in 1989, where121
it has spread from the mouth of the Colorado River to Veracruz, Mexico. This
species likely arrived in ballast water of a vessel from Latin America. The brown
mussel is a biofouler (i.e., it attaches to exposed solid surfaces) and is therefore likely
to clog water and power plant intakes, similar to the zebra mussel. However, only
limited damage has been reported thus far along the Gulf Coast. For more
information, see
[ Waves/v12n3/abstract-3.html] ,
[], and
[ nis/ nis/Perna_perna.html] .

121 The west has two major rivers called “colorado” (“reddish” in Spanish). This one flows
from west central Texas to the Gulf Coast, southwest of Galveston.

Asian River Clam, Corbicula fluminea. This clam has a huge natural
range from temperate and tropical southern Asia west to the east coast of Africa, plus
the eastern Mediterranean, plus southeast Asian islands south into central and eastern
Australia. This species was introduced into the United States in 1938 as a food item
used by Chinese immigrants. Since its first collection along the banks of the
Columbia River near Knappton, Washington, it has spread into major waterways of

38 states and the District of Columbia by a combination of bait bucket introductions,

accidental introductions associated with imported aquaculture species, and
intentional introductions by people who buy them as food. This species’ most
prominent effect has been biofouling, especially of complex power plant and
industrial water systems, but also of irrigation canals, pipes, and drinking water
supplies. It alters the bottoms of streams and lakes, thereby damaging habitat for a
number of species, and competes with native species for limited resources.
Estimated annual damage is about $1 billion.122 For more information, see
[] and
[ publicat/nespp_4.htm] .
New Zealand Mud Snail, Potamopyrgus antipodarum. A native of
New Zealand, but long established in Australia and Europe, this species was
discovered in North America in 1987 in Idaho’s Snake River. Between Shoshone
Falls and the C.J. Strike Dam, population levels may exceed 100,000 snails per
square meter. This species was discovered in Lake Ontario in 1991, has also been
found in Montana’s Madison River, and most recently was detected in the Colorado
River drainage. Ballast water transfer is the suspected source of this species.
However, birds and sport anglers may also be spreading this pest to additional
drainages. Although no effects on native species have yet been observed, scientists
are concerned about competition with native mollusks for resources and habitat
because of the mud snail’s high reproductive rate. For more information, see
[ h t t p : / / www. fcs c . / N ew_ Zeal an d _
Mudsnail/new_zealand_mudsnail.html] and
[ kers/mollusks_new_z ealand_mudsnail.
Sea Lamprey, Petromyzon marinus. This species is generally marine but
ascends freshwater rivers to spawn along the Atlantic Coast from Labrador to the
Gulf of Mexico. This species was first reported in Lake Ontario in 1835, in Lake Erie
in 1921, in Lake Michigan in 1936, in Lake Huron in 1937, and in Lake Superior in
1946. The sea lamprey may have entered Lake Ontario from its native habitat in the
Atlantic drainage by migrating through the Erie Canal after the canal was opened
between 1819 and 1825 or by hitching rides on boats passing through the Erie or St.
Lawrence canal systems. Later, it entered the upper Great Lakes through the Welland
Canal around Niagra Falls. Adult lampreys attack and parasitically feed on other
fishes such as lake trout, often resulting in death of the prey, either directly from the
loss of fluids and tissues or indirectly from secondary infection of the wound.

122 N. C. Balcom. Aquatic Immigrants of the Northeast, No. 4: Asian Clam, Corbicula
fluminea.” (Groton, CT: Connecticut Sea Grant College Program, 1994).

Progressively over the last 150 years, the sea lamprey caused the extinction of three
species of endemic ciscoes (whitefish) in the Great Lakes, and drove lake trout and
several other species to near extinction. Both recreational and commercial fisheries
suffered major economic loss, with additional indirect losses in tourism and
supporting businesses. Congress regularly considers the impacts of sea lamprey
during debate on annual appropriations for the Great Lakes Fishery Commission for
the U.S. share of sea lamprey control expenses with Canada (Department of State
appropriations for “International Fishery Commissions”). The annual cost of
international control programs for sea lamprey in the Great Lakes drainage is
approximately $10 million to $15 million. For more information, see
[] and
[ .gov/fishes/accounts/petromyz /pe_marin.html] .
Alewife, Alosa pseudoharengus. The alewife may have been native to
Lake Ontario or could have reached the lake in the mid-1800s. Subsequently, this fish
has spread through the Great Lakes via the Welland Canal, with first reports from
Lake Erie in 1931, Lake Huron in 1933, Lake Michigan in 1949, and Lake Superior
in 1954. The species was intentionally stocked in other inland waters. The
disappearance of native plankton-eating fish, such as whitefish, in the Great Lakes
has been attributed in part to the introduction of alewives, which reduce zooplankton
populations. Some attribute the extinction of the lake herring and the decline of chub
species in the Great Lakes to the alewife. Today, the alewife is the dominant fish in
Lake Michigan, where it accounts for 70-90% of the fish weight (biomass). Pacific
salmonids were introduced to the Great Lakes in the mid-1960s, in part as an attempt,
albeit unsuccessful, to control the alewife populations. Alewives have damaged sport
and commercial fisheries in the Great Lakes by eliminating certain species such as
lake herring and emerald shiner, and have damaged tourism by undergoing periodic
large-scale die-offs that litter beaches with rotting fish, posing both a nuisance and
a health hazard. Costs of cleaning beaches have declined in recent years with reduced
populations of alewives. For more information, see:
[] and
[ h ttp://] .
Round Goby, Neogobius melanostomus. Native to Eurasia including
the Black Sea, Caspian Sea, and Sea of Azov and their tributaries, the round goby
was first discovered in Michigan’s St. Clair River in 1990. This fish species
probably arrived in freighter ballast water. The species appears to be undergoing a
population explosion in Lakes Erie, Huron, and Michigan. The round goby was first
observed in Lake Superior in 1995. The round goby is aggressive, feeding
voraciously upon small bottom-dwelling fishes (e.g., sculpins, darters, and logperch),
snails, mussels and aquatic insects. Abundance of native fish species has declined
in areas where this goby has become abundant, with sculpins particularly affected.
Thus, there is concern that the round goby may harm sport and commercial fisheries
in the Great Lakes as well as indirectly affect tourism. The Army Corps of Engineers
has constructed an underwater electric barrier in the Chicago Sanitary and Ship Canal
in an attempt to prevent the round goby and other species from moving between the
Great Lakes and the Mississippi River drainage. For more information, see
[] and
[ h ttp://] .

European Ruffe, Gymnocephalus cernuus. This fish is native to
Northern Europe and Asia. The ruffe was first observed in 1986 in the St. Louis
River along the border between Minnesota and Wisconsin. It has since spread into
Duluth Harbor in Lake Superior and several tributaries of the lake. By 1994, the
ruffe had spread eastward along the Lake Superior shoreline as far as Michigan’s
Ontonogan River, and was observed in Lake Huron in 1995. The ruffe was probably
introduced from ship ballast water as early as 1982-1983. Ruffe have the potential
to compete with native fishes, such as yellow perch, and could consume large
quantities of eggs of commercially important lake whitefish and similar species.
Thus, the major effect of this species may be on sport and commercial fisheries as
well as indirectly on tourism. For more information, see:
[ .gov/fishes/accounts/percidae/gy_cernu.html] ,
[], and
[ h ttp://] .
Common Carp, Cyprinus carpio. Native to Asia, this species dispersed
naturally into the Danube River where it gave rise to fish that the Romans moved
around their Empire.123 From Europe, this fish was introduced into the United States
as a sport fish in the 1850s. Carp are currently found in every state except Alaska.
Carp are bottom-feeders, destroying aquatic plants and increasing suspended
sediments as they feed. Overabundant carp can severely deplete lake bottom food
sources needed by species sought by sport anglers, such as yellow perch, bluegills,
and channel catfish. Although carp are sought by some recreational anglers, most
view carp as damaging sport fisheries for a variety of native species. For more
information, see:
[] and
[ h ttp:// .gov/fishes/accounts/cyprinid/cy_ carpi.html] .
Walking Catfish, Clarias batrachus. Walking catfish were imported to
Florida, reportedly from Thailand, in the early 1960s for the aquarium industry. The
first introductions apparently occurred in the mid-1960s when adult fish imported as
brood stock escaped in Broward County. Additional introductions in Florida,
apparently purposeful releases, were made by fish farmers in the Tampa Bay area in
1967-1968, after the state banned the importation and possession of this species. The
species can migrate overland at night or during rain, which has allowed it to spread
to 20 counties in southern Florida. Although aquarium releases are apparently
responsible for subsequent discoveries in California, Nevada, Georgia,
Massachusetts, and Connecticut, this species is not believed to have become
established outside Florida. In Florida, walking catfish have invaded fish farms,
where they enter culture ponds and prey on fish. However, no studies are known to
have measured the ecological or economic impacts of this species. For more
information, see [] and
[ h ttp:// s/clarias_batrachus.htm] .
Snakeheads, Channidae. This freshwater fish from tropical Africa and
southern Asia has recently become a concern in the United States. Because this fish

123 Eugene K. Balon. Domestication of the carp, Cyprinus carpio L. Misc. Pub., (Toronto:
Royal Ontario Museum, Life Sciences Div., 1974) 37 p.

can tolerate low oxygen conditions and is capable of overland migration by wriggling
movement, it can spread to and occupy a variety of habitats. All life stages of
snakeheads are highly competitive predators, with adults feeding on many species,
including other fish, crustaceans, frogs, small reptiles, and sometimes birds and
mammals. In the United States, four species of snakeheads have been recorded in the
wild in seven states (California, Florida, Hawaii, Maine, Maryland, Massachusetts,
and Rhode Island), and two of these species have established reproducing
populations in Hawaii and Florida. Between 1997 and 2000, more than 15,000 live
snakeheads were imported into the United States. On July 26, 2002, FWS proposed
amending 50 CFR 16.13 to add snakeheads to the list of injurious fish, mollusks, and
crustaceans, thus prohibiting their interstate transportation and importation into the
United States.124 For more information, see
[] and
[ h ttp://www.fcsc.usgs .gov/Nonindi genous_Species/Snakehead1.pdf] .
Rainbow Trout, Oncorhynchus mykiss. This species has been introduced
widely outside its historic range along the North American Pacific Coast, and
introduced populations have been implicated in the disappearance of native fauna
(e.g., aquatic invertebrates). Stocking of rainbow trout for sport anglers in high
altitude lakes in areas such as Yosemite National Park has been a controversial
practice because of the impact on native fauna. Rainbow trout have also hybridized
with subspecies of cutthroat trout in Nevada and interior western states, disrupting
native gene pools. For more information, see
[ h ttp://] ,
[], and
[ oes/rls/rpts/ocns/2322.htm] .
Lake Trout, Salvelinus namaycush. In 1993, lake trout were discovered
in Yellowstone Lake in Yellowstone National Park, where they threaten native
cutthroat trout. Lake trout probably entered Yellowstone Lake by illegal human
introduction as early as the late 1970s or early 1980s. The lake trout’s native range
includes most of the northern-tier states from Maine to Minnesota and across Canada
into Alaska. Tourism and sport fishing for native trout could be harmed by this
introduction. Cutthroat trout in Yellowstone National Park are the focus of a
recreational fishery valued at $36 million annually, as well as an important prey for
species such as bald eagles and some grizzly bears during the cutthroat’s spring
spawning season. For more information, see
[] and
[ h ttp:// s/z / a/z ak100/LKTcontrol.htm] .
Coqui, Eleutherodactylus coqui. The coqui is a small nocturnal frog
native to Puerto Rico, where it is a revered symbol of the island. It is active in trees
in moist areas, and hides during the day under ground cover. It lays its eggs in any
damp place. The eggs hatch directly into tiny tailed frogs, undergoing the normal
tadpole stage of most frogs while still in the egg. Adult frogs reach 1-2 inches. They
are active at night or on rainy or overcast days. Only males call, from a perch usually

3 to 6 feet about the ground; the common name is taken from the unusually loud

124 67 Federal Register 48855-48864.

sound of this two-note call. Its primary means of transport is via the shipment of
horticultural specimens. The species was introduced, probably by accident, at
Fairchild Tropical Garden in Miami in the 1970s, and is still present in the area
though apparently mainly in greenhouses. It may also be present around New
Orleans. It is established in the Virgin Islands.
In the 1990s, it became established in Hawaii, to the tremendous annoyance of
residents, due to the loud calls which can reach 100 decibels. Its broader effects
probably include predation on local insect populations and therefore competition with
other native insectivores, including birds. Since many resident Hawaiian species are
already under threat from still more invaders (e.g., malarial parasites, mongooses,
rats, pigs, non-native birds, etc.), this competition for food could be especially
threatening. The state government has asked for cooperation from the state’s large
horticulture industry in preventing further spread of the species. Caffeine (in a 99%
pure and highly toxic form) is in experimental use as a control around non-food
plants. For more information, see
[ AlienSpeci es InHawaii/speci es /frogs /]
Brown Tree Snake, Boiga irregularis. The brown tree snake was
introduced to Guam where it is now extremely abundant and has damaged the
electrical and telephone grids. It has preyed on several endemic Guamanian birds so
severely as to cause their extinction in the wild. Estimated losses due to power125
outages alone on Guam are at least $1 million per year. It poses a serious threat to
Hawaii and its tourism industry, since snakes are not hesitant to enter homes or
hotels; though their venom is weak, over 200 Guamanians have been bitten, usually
when snakes crawled into sleepers’ beds. Native Hawaiian birds, having evolved in
a snakeless environment, would also be at serious risk (and Hawaiian non-native
birds would enjoy yet another advantage over the native birds). The problems caused
by this species are covered in CRS Report 97-507 ENR, Non-Indigenous Species:
Government Response to the Brown Tree Snake and Issues for Congress. Also see
[], and for Hawaiian problems
specifically, see [].
Indian Mongoose, Herpestes auropunctatus. In the late 1800s, sugar
cane growers in Hawaii and Puerto Rico sought ways to control the damage that
introduced rats were causing to the crops. In what would prove to be a misguided
attempt at biological control, they imported the Indian mongoose, a small predatory
mammal native to Asia. The mongooses failed to control the rats but instead
decimated native birds and other species, probably causing the extinction of some.
In Puerto Rico and other Caribbean islands, mongooses are a major vector for rabies,
and in some parts of Hawaii, they damage papaya and banana crops. They now occur
on four of the five major Hawaiian islands, Kauai being the only exception. Control
efforts costing millions of dollars per year have so far not succeeded in eliminating
mongooses from any of those islands.126 For more information, see:
[http:/ / danoff-burg/invasion_bio/inv_spp_summ/Herp
estes_auropunctatus.html] .

125 Pimentel report.
126 Pimentel report.

Nutria, Myocastor coypus. Nutria (relatives of beavers) were introduced
to the United States from South America in 1899 to stimulate the fur industry. Some
animals escaped after a hurricane, and later when the industry failed, surplus animals
were released. The highly prolific, semi-aquatic species is now established in 22
states, and has been sighted in many more. It has no natural enemies, and remaining
fur trappers have not kept pace with its exploding population growth.127 It has
severely damaged marsh vegetation which causes conversion of heavy vegetation to
open water, thereby removing nesting or overwintering habitat for many birds, and
eliminating habitat critical to the juvenile stages of important commercial species
such as shrimp, crabs, oysters, many species of young fishes, and others. It has been
very destructive in Gulf Coast states and the mid-Atlantic states, primarily on the
Delmarva Peninsula. After a hearing before the House Resources Committee (Ser.
No. 105-97), Congress passed legislation (P.L. 105-332) to assist Maryland in
controlling nutria populations. For more information, see
[], or, for Blackwater National
Wildlife Refuge (MD) specifically, see
[ h ttp://www.pwrc.usgs .gov/resshow/nutria.htm] .

127 One reviewer, E.A. Allison of the University of East Anglia, reports that after a 30 year
effort, the species was eradicated from marshes in that area of the United Kingdom.
(Personal communication, May 1999.)

Appendix A: List of Acronyms
ACEArmy Corps of Engineers
ANSAquatic nuisance species
APHISAnimal and Plant Health Inspection Service
ARSAgricultural Research Service
ASPEAAlien Species Prevention and Enforcement Act
BIABureau of Indian Affairs
BLMBureau of Land Management
BORBureau of Reclamation
BWMBallast water management
BWTBallast water treatment
CDBConvention for Biological Diversity
CDCCenters for Disease Control and Prevention
CECCommission on Environmental Cooperation
CEQCouncil on Environmental Quality
CENRCommittee on Environment and Natural Resources Research
CFRCode of Federal Regulations
CITESConvention on International Trade in Endangered Species of Wild
Fauna and Flora
CSREESCooperative State Research, Education, and Extension Service
DODDepartment of Defense
DOIDepartment of the Interior
EEZExclusive Economic Zone
EIFACEuropean Inland Fisheries Advisory Commission
EISEnvironmental Impact Statement
EPAEnvironmental Protection Agency
ERSEconomic Research Service
FAAFederal Aviation Administration
FAOFood and Agriculture Organization
FHwAFederal Highway Administration
FICMNEWFederal Interagency Committee for Management of Noxious and
Exotic Weeds
FSForest Service
FSAFarm Service Agency
FWSFish and Wildlife Service
GISPGlobal Invasive Species Program
GLERLGreat Lakes Environmental Research Lab
ICESInternational Council for the Exploration of the Sea
ICSUInternational Council of Scientific Unions
IMOInternational Maritime Organization
IPMIntegrated pest management

IUCNInternational Union for the Conservation of Nature
MARPOLInternational Convention on Marine Pollution
MEPCMarine Environmental Protection Committee
NANPCANon-indigenous Aquatic Nuisance Prevention and Control Act
NBICNational Ballast Information Clearinghouse
NBIINational Biological Information Infrastructure
NEPANational Environmental Policy Act
NISANational Invasive Species Act
NISCNational Invasive Species Council
NMFSNational Marine Fisheries Service
NOAANational Oceanic and Atmospheric Administration
NOBOBNo ballast on board
NPSNational Park Service
NRCSNatural Resources Conservation Service
NSFNational Science Foundation
NSTCNational Science and Technology Council
NWRSNational Wildlife Refuge System
ORDOffice of Research and Development
OSMOffice of Surface Mining Reclamation and Enforcement
OSTPOffice of Science and Technology Policy
OTAOffice of Technology Assessment
P.L.Public Law
PPAPlant Protection Act
RAGRemoval of aquatic growth
SCOPEScientific Committee on Problems of the Environment
SERCSmithsonian Environmental Research Center
UNESCOUnited Nations Environment Programme the Secretariat for the
Convention on Biological Diversity
USCGU.S. Coast Guard
USGSU.S. Geological Survey
USTRUnited States Trade Representative
WBCAWild Bird Conservation Act
WSWildlife Services (in APHIS)

Appendix B: Federal Agency Funding
for Invasive Species
FY2000-FY2003 Request ($ in thousands)
Agency FY2000 FY2001 FY2002 Request
Department of Agriculture
Agricultural Research74,71681,207107,88695,889
Animal and Plant664,045956,082825,387915,485
Health Inspection
Cooperative State12,19118,75013,23511,787
Research, Education,
and Extension Service
Economic Research30002,000
Farm Service Agency1280000
Forest Service35,21955,38061,13081,683
Natural Resources1,6001,6001,5451,313
Conservation Service
Office of the Chief129258438438438
Department of Commerce
National Oceanic and1,6501,7503,250800

Atmospheric 130
128 The Farm Service Agency does not have funding for invasive species work. It only
requires farmers signing up for conservation programs to control invasive species on the
enrolled acres.
129 The USDA Office of the Chief Economist advises the Secretary on the economic
implications of Department policies, programs, and proposed legislation. These amounts
represent the portion of the Office’s budget allocated to economic analysis of invasive
130 In addition to the funding shown, GLERL spends between $400,000 and $500,000
annually on invasive species from its base funds.

Agency FY2000 FY2001 FY2002 Request
National Sea Grant3,0001322,9933,0000
College Program131
Department of the Interior
Bureau of Indian1,9781,9942,0072,012
Affairs 133
Bureau of Land7,9508,9309,1608,200
Bureau of Reclamation2,1122,0622,1802,129
Fish and Wildlife7,56314,42115,12215,185
Geological Survey5,1847,6007,8007,300
National Park Service1341,2001,2001,8002,145
Office of Surface0102550
Mining Reclamation
and Enforcement
Other Departments
Army Corps of12,60012,00011,2000
Engi neers 135
Department of State012,14912,24812,000

131 The Administration’s FY2003 budget request proposed transferring the Sea Grant
program to the National Science Foundation, and consequently, the request does not
specifically include funding for invasive species activities. No FY2003 appropriations bill
for the Commerce Department has yet been filed in the House, but the Senate bill (S. 2778)
requires that Sea Grant remain in NOAA. (See CRS Report RL31309.)
132 In addition, Sea Grant universities were calculated to have spent about $586,000 from
core funds on invasive species research.
133 This is the Noxious Weed Control program. Some weeds may be native to North
America. The is no formal national program for control of non-native animals.
134 NPS figures are for Exotic Plant Management Teams only. Other invasive species efforts
(e.g., for animals and some aquatic plants, as well as a few terrestrial plants) are funded as
parts of the budgets of individual park system units. Aggregate figures for these efforts are
difficult to obtain, but according to NPS officials represented about 18% of the NPS
FY2002 budget of $18 million for the Natural Resource Challenge program.
135 The Corps estimates that the figures for FY2000 to FY2002 are $12.6 to $22.6 million,
$12.0 to $22.0 million, and $11.2 to $21.2 million, respectively. No figures are available
for the FY2003 request.

Agency FY2000 FY2001 FY2002 Request
Coast Guard3,9974,0924,0524,093
Federal Aviation0000
Federal Highway10027560n/a
Council on0000
Office of Science and0000
Technology Policy
Office of the U.S. Trade0000
Environmental 450 500 4,000 500
Protection Agency
National Science18,06011,8609,0001388,000139
Smithsonian Institution2,1803,1844,0793,915
Total 858,0831,200,4781,100,6061,176,927
n/a = not available

136 Figures include only expenditures for research, conferences, and publications.
Vegetation management is state-funded and the share of unmarked federal highway funds
used is not known. Of the total shown over the 3 years, $325,000 was used for research,
$50,000 for a field guide to invasive roadside plants, and $60,000 for a North American
137 For this and the following two agencies, it is essentially impossible to name a figure
associated with invasive species. The difficulty lies in the diffuse and variable nature of
their responsibilities.
138 NSF estimates between $8 million and $10 million.
139 NSF states the amount is dependent upon proposals received, but estimates that the figure
will be between $8 million and $10 million.