[Editor's Note: please also see Detailed Discussion of the Ethical Treatment of Invasive Species by Bradley Varner (2022).]
Invasive species are a growing problem and, according to invasive expert and director of the University of Notre Dame’s Center for Aquatic Conservation David Lodge, one of the most “irreversible kinds of pollution”; it is now possible to reverse many chemical forms of pollution, but biological forms of pollution are extremely difficult if not impossible to reverse. As the impact of invasive species is expected to increase with growing global travel and trade, ecologists, farmers and government agencies around the world are increasingly concerned about the threats this creates to the local ecology, economy and health of the population. But devising policies to curtail or prevent invasive species has turned out to be a challenge that is almost as complex as nature itself. (Aliens on the Shore, Science and Society, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1319213/ ) Addressing the problems associated with invasive species also creates a further concern over whether eradication methods are humane.
This paper will introduce the concept of invasive species and give examples of how they threaten the economy and ecosystem and human health. It then examines the federal laws that address invasive species, as well as examples of state responses to invasive species. The methods of control and eradication of invasive species are explained. Finally, the paper discusses the impact that these laws and methods have on animal welfare.
II. What are Invasive Species and Why are They a Concern
In 1999, President Clinton recognized that invasive species are one of the most serious threats to biodiversity when he passed Executive Order 13112 . The order was signed in response to the over 123 billion dollars of damage that was estimated to have been done annually in the United States by invasive species. Invasive species such as zebra mussels and brown tree snakes shut down electrical utilities and caused power outages. Invading sea lampreys caused the collapse of lake trout and other Great Lakes fisheries.
But what is an invasive species? Executive Order 13112 of February 3, 1999 defines “invasive species” as an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health. The executive order defines “alien species” as any species, with respect to a particular ecosystem, including its seeds, eggs, spores, or other biological material capable of propagating that species, that is not native to that ecosystem.
Invasive Species introduced into the United States from around the globe affect plant and animal communities on our farms, ranches and coasts; and in our parks, waters, forests, and backyards. As global climate patterns shift, the distribution of species will change, and so will the susceptibility of particular habitats to the impacts of new species introductions. Human activity such as trade, travel and tourism have all increased substantially, increasing the speed and volume of species movement to unprecedented levels. Invasive species are often unintended hitchhikers on cargo and other trade conveyances. Still more species are deliberately introduced as pets, ornamental plants, crops, food, or for recreation, pest control or other purposes. ( 2008-2012 National Invasive Species Management Plan , National Invasive Species Council, http://www.oar.noaa.gov/oceans/2008-2012NationalInvasiveSpeciesManagementPlan.pdf ).
A. Non-native Species
A non-native species is not necessarily an invasive species. A non-native, or alien, species may be benign or interfere minimally with the native ecosystem. A non-native species must cause, or be likely to cause, economic or environmental harm or harm to human health in order to be considered an invasive species. ( Executive Order 13112 ).
Zebra mussels are the quintessential example of invasive species in the U.S.A. However, there are thousands of invasive species. Asian Carp is the latest invasive species threat to the Great Lakes. The gypsy moth, which was introduced in the U.S.A. in the 1800’s is one of North America’s most devastating forest pests. (U.S. Forest Service, Gypsy Moth in North America , http://www.fs.fed.us/ne/morgantown/4557/gmoth/ ). While Asian carp, gypsy moths and zebra mussels hog invasive-species headlines, a Science Daily Article explains that many invisible invaders are altering ecosystems and flourishing outside of the limelight; invasive microbes have many of the same traits as their larger, 'macro' counterparts and have the potential to significantly impact terrestrial and aquatic ecosystems. ( http://www.sciencedaily.com/releases/2010/12/101207143216.htm ). Global change can exacerbate microbial invasions, so they will likely increase in the future.
B. Feral Species
Feral animals are sometimes considered invasive species. For example, in 2011, the Daily Tribune reported that the Michigan Department of Natural Resources and Environment declared the bristly swine an invasive species. The pigs are widely believed to have escaped from game farms and hunting preserves. Feral pigs eat anything and everything, including endangered wild plants, the eggs of game birds, young deer or lambs, reptiles and farm crops. Nationwide, the U.S. Department of Agriculture estimates they cause about $800 million in damage each year to agriculture. The pigs also can carry diseases including bovine herpes virus, swine fever, foot and mouth disease, influenza, anthrax and swinepox virus. ( http://www.dailytribune.com/articles/2011/02/05/news/doc4d4dd622bc70c874631975.txt ).
C. Exotic Pets
One particular human activity has resulted in the spread of many invasive species: the release of exotic pets. For example, Burmese pythons became established in Florida because of the pet trade. The Burmese python is known to prey on at least 20 native species. (Note that FL ST 379.372 now prohibits the keeping, possession, importation, sale, and breeding of the Burmese python in addition to several other python species). Lionfish are another example; this venomous species is native to the Pacific Ocean but is now also found off the Atlantic Coast in states like Florida, Georgia and North Carolina. Lionfish likely became established by pet owners dumping the fish into the sea. This predatory fish poses a significant threat to coral reef and mangrove ecosystems because it both preys on and competes for food with native, marine wildlife. ( South Florida 2011 Environmental Report , http://my.sfwmd.gov/portal/page/portal/pg_grp_sfwmd_sfer/portlet_prevreport/2011_sfer/executive_summary.pdf ; Invasive Species: unwanted exotic pets becoming invasive species , The Conservation Report, http://conservationreport.com/2008/04/29/invasive-species-unwanted-exotic-pets-becoming-invasive-species/ ).
III. Invasive Species Laws
Invasive species populations span geographic and jurisdictional boundaries; thus efforts to manage invasive species must be coordinated across boundaries. Battling invasive species is not something that can be done by one agency or organization. Federal, state, local and tribal governments, as well as non-governmental organizations, academic institutions, and the public, work together to control invasive species. (2008 -2012 National Invasive Species Management Plan , National Invasive Species Council, http://www.oar.noaa.gov/oceans/2008-2012NationalInvasiveSpeciesManagementPlan.pdf ).
A. Federal Laws
While no one law addresses all the concerns of invasive species, many federal laws address some aspect of invasive species. These laws date as far back as 1900, with the Lacey Act, which has a provision to curtail the introduction of injurious species. They also include the Nonindigenous Aquatic Nuisance Prevention and Control Act (16 USC 4701 - 4751), passed in 1990, and the Executive Order 13112 , issued in 1999. The Act created a Task Force to control aquatic invasive species, and the Executive order created a council to coordinate actions taken against invasive species. Most recently, Congress is responding to a potential invasive threat in the Great Lakes. Senate Bill 1421 , the Asian Carp Prevention and Control Act, was signed into law in December 2010.
1. The Lacey Act
The injurious wildlife provisions of the Lacey Act are one tool that the U.S. Fish and Wildlife Service (Service) uses to prevent illegal introductions of and to manage invasive species. Under the Lacey Act , importation and interstate transport of animal species determined to be injurious may be regulated by the Secretary of the Interior. The Service implements the injurious wildlife provisions ( 18 U.S.C. 42 ) through regulations contained in 50 CFR part 16. Species are added to the list of injurious wildlife to prevent their introduction or establishment through human movement in the United States to protect the health and welfare of humans, the interests of agriculture, horticulture or forestry, and the welfare and survival of wildlife resources from potential and actual negative impacts. ( Injurious Wildlife Fact Sheet , U.S. Fish and Wildlife Service, http://www.anstaskforce.gov/Documents/Injurious_Wildlife_Fact_Sheet_2007.pdf ) The injurious provisions of the Act were included in its original passage in 1900. (Robert S. Anderson, The Lacey Act: America's Premier Weapon in the Fight Against Unlawful Wildlife Trafficking , 16 Public Land L. Rev. 27 (1995).
2. Executive Order 13112
The Executive Order created the National Invasive Species Council and the Invasive Species Advisory Committee, which work together with stakeholders, concerned members of the public, and member departments to address invasive species. The Council is made up of federal agencies. The Committee is a group of non-federal experts and stakeholders. Together, they formulated an action plan for the nation.
The Council issued the National Invasive Species Management Plan in 2001 to provide an overall blueprint for Federal action. The Plan recommended specific action items to improve coordination, prevention, control and management of invasive species by the Federal agency members of the Council. More recently the Council issued its 2008 Plan, which focuses on five “Strategic Goals”: Prevention; Early Detection and Rapid Response; Control and Management; Restoration; and Organizational Collaboration ( See http://www.invasivespecies.gov/main_nav/mn_NISC_ManagementPlan.html ). To accomplish these strategic goals, critical support for efforts such as research, data and information management, education and outreach, and international cooperation elements are included in pertinent sections of the 2008 Plan. The 2008 Plan is not a comprehensive list of all federal invasive species actions. It is a targeted set of priority strategic action plans with objectives and implementation tasks that are intended to be completed in the next five years. The over-arching strategic goals and strategic action plan objectives remain consistent with the 2001 Plan. The accomplishment of specific implementation tasks and performance elements will be dependent upon agency budgets, and in some cases, legal or regulatory changes.
3. Nonindigenous Aquatic Nuisance Prevention and Control Act
Although the Act was passed in response to zebra mussels, the Act focuses on all aquatics, including aquatic plants. The Aquatic Nuisance Species Task Force is an intergovernmental organization, administered by the Fish and Wildlife Service, committed to preventing and controlling aquatic nuisance species and implementing the Nonindigenous Aquatic Nuisance Prevention and Control Act . The Task Force coordinates Federal governmental efforts dealing with aquatic nuisance species with those of state and local governments, non-governmental organizations, academic institutions, and the private sector. The Act also mandated that the Task Force undertake a program to control the brown tree snake, which had damaged native wildlife populations in Guam. This program also focused on preventing similar harm from the brown tree snake in Hawaii. The Fish and Wildlife Service recognizes that battling invasive species is not something that can be done by one agency or organization. Federal, state, local and tribal governments, as well as non-governmental organizations, academic institutions, and the public, must work together to get ahead of new infestations like giant salvinia (a floating fern) before they reach uncontrollable levels.
5. The Asian Carp Prevention and Control Act
The Act would prohibit the importation and shipment of certain species of carp (would amend injurious species provisions of 18 U.S.C. 42 ). (See S.B. 1421 ). According to Representative Dave Camp, the bill’s sponsor, it would also require the speedy creation of an action plan to permanently separate Lake Michigan from the Chicago Area Waterway System, where experts believe Asian Carp could enter and cause irreparable harm to the Great Lakes.
B. State Laws
States also enact legislation in order to combat the introduction and spread of invasive species. Nineteen states now have invasive species councils or similar bodies. ( Five-Year Review of Executive Order 13112 on Invasive Species , The National Invasive Species Council, http://www.invasivespeciesinfo.gov/docs/council/fiveyearreview.pdf ) However, state laws focus mainly on plant invasive species, not animal invasive species. For example, the Florida Department of Environmental Protection Regulation allows control invasive exotic plants where appropriate for the restoration, maintenance, and preservation of native plant communities. (Park Property and Resources Rule, 62D-2.013, https://www.flrules.org/gateway/ruleNo.asp?id=62D-2.013 )
Michigan is an example of a state that goes beyond plants in regulating invasive species. The Michigan Commission of Natural Resources maintains a list of prohibited or restricted species. According to Michigan law, a person may not knowingly possess a species on the list. Additionally, a person shall not introduce a prohibited species, a restricted species, or a genetically engineered or nonnative aquatic plant, bird, crustacean, fish, mammal, or mollusk unless the introduction is authorized by law. (Natural Resources and Environmental Protection Act, Transgenic and Nonnative Organisms, MCLS § 324.41301-324.41305).
An Environmental Law Institute study, Strategies for Effective State Early Detection/Rapid Programs for Plant Pests and Pathogens, found that most states have well-developed regulations governing pest response in agricultural and horticultural contexts. However, the expansion of pests into urban and other nonagricultural environments has created new challenges for pest control authorities. ( http://www.elistore.org/reports_detail.asp?ID=11223 )
Another Environmental Law Institute study that reviewed developments in state laws and regulations governing invasive species in eleven states, Status and Trends in State Invasive Species Policy: 2002-2009, found that invasive species laws and regulations are often fragmented and incomplete and have developed primarily on a species-by-species basis in response to crisis. ( http://100thmeridian.org/documents/ELI_Invasive_Species_State_Policy_Report_05_2010.pdf )
As a result, the study says they often fail to address potential future invaders or close off known invasion pathways. However, states have begun regulating invasion pathways and identifying species that may become invasive in the future due to climate change or other factors, and states are increasingly creating interagency councils and management plans to coordinate these novel invasive species responses.
IV. Invasive Species Animal Welfare Issues
While the impetus of federal and state laws focuses on the eradication of invasive species and the protection of native biodiversity, there are inherent concerns over the eradication methods used and their impact on the invasive animals themselves. This section details how state laws address the welfare of invasive species, the methods used for control and eradication, as well as the impacts of those methods on invasive species.
A. Some States Exempt Invasive Species from their Cruelty Laws
Almost every state has a law prohibiting cruelty to animals. The laws do not explicitly mention invasive species, but many do reference pests. Many of the laws have exemptions for pests, impliedly allowing these animals to be killed inhumanely. Twenty two states have some form of an exemption relating to pests. Some states broadly exempt pest species, and some exempt poisoning of pest species specifically owners’ land. At least one state, Vermont , allows the destruction of pests on an owner’s property to be used as an affirmative defense. Other state laws don’t reference pests but allow for the destruction of dangerous animals or the lawful destruction of animals for the purposes of protecting the public, other animals, or public health. Such states include Georgia ( GA ST § 16-12-4 ), which specifies that persons are not prohibited from injuring or killing an animal reasonably believed to constitute a threat for injury to livestock or poultry, and North Carolina ( NC § 19A-1.1 ), which allows the lawful destruction of any animal for the purposes of protecting the public. The legislators’ intent to include invasive species as pests is unclear, but the myriad exemptions for pests do raise the legal possibility that invasive species are themselves exempted.
Additionally, invasive species may be excluded from cruelty laws because many invasive species are invertebrates, which are often excluded from the cruelty laws’ definition of “animal." For example, Washington defines “animal” for purposes of its cruelty law as “any nonhuman mammal, bird, reptile, or amphibian.” ( WA ST 16.52.011(1)(b) ) Similarly, Arkansas defines “animal” for its cruelty laws as “any living vertebrate creature, except human beings and fish.” ( AR ST 5-62-102(2) )
B. Mute Swan Case Study: Invasive Species Excluded from Federal Protection
Invasive species, by virtue of being non-native species, may also excluded from some federal protections, such as the Migratory Bird Treaty Act . Mute swans are believed to have been first introduced into the U.S. for display on ponds and lakes almost 200 years ago. During the 1990s, Maryland residents began voicing concerns about an increase in conflicts with swans and the swans’ aggressive behavior. Citizens also began providing anecdotal complaints that mute swans were overgrazing on submerged aquatic vegetation, which are underwater plant communities that are critical for the proper functioning of the Chesapeake Bay. In response, the Maryland Department of Natural Resources proposed a program to reduce the mute swan population by half, primarily by shooting the animals. Federal law protects migratory birds; however, the Fish and Wildlife Service maintains a list of nonnative species not covered by the Act. The FWS issued a final rule including mute swans on the list of birds not covered by the Act. ( Swan Song? Giving a Voice to Mute Swans in the Chesapeake Bay , Michael Markarian and Jonathan R. Lovvorn, Esq., 11 U. Balt. J. Envtl. L. 115 (Spring, 2004)). An animal protection organization sued to prevent the FWS from killing the swans, but the court decided in favor of the agency, ruling that the nonnative species is indeed not protected by federal law. ( Fund for Animals, Inc. v. Kempthorne , 472 F.3d 872 (D.C. Cir. 2006)).
C. Several Control Methods Can Be Used
When an invasive species first becomes introduced into a new area, there may be a chance to eradicate it through a rapid response action if it is detected in time. If eradication is not possible, then the species may be subject to control and management efforts. Regardless of whether the goal is eradication or control/management, there are a suite of different options available. When making decisions on which options to use, one must use an Integrated Pest Management approach to choose the options which will be the most environmentally sound yet still affect the invasive species as strongly as possible. ( Frequently Asked Questions About Invasive Species , U.S. Fish & Wildlife Service, http://www.fws.gov/invasives/faq.html ). The various options for eradication/control/management include:
- Physical or Mechanical Control - This type of control involves physically removing the invasive species (i.e. harvesting) or using barriers or traps to prevent their spread or to capture them. For invasive plants, mowing is another example of physical control.
- Chemical Control - This type of control involves all sorts of pesticides. Although chemical use can be very effective, they can be very dangerous to other species or to the ecosystem in general and must be used in an environmentally sound manner. The key is to choose chemicals that are low-risk yet effective and that can be applied when the pest is at its most vulnerable.
- Cultural Management - Cultural management is the manipulation of the habitat in ways that increase the mortality of the invasive species or reduce its rates of increase and damage. Cultural management that can affect invasive species including: selection of pest resistant varieties of crops, mulching, winter cover crops, changing planting dates to minimize insect impact, burning, flooding, crop rotations that include non-susceptible crops, moisture management, addition of beneficial insect habitat, or other habitat alterations that help the native species compete better against the invasive ones.
- Biological Controls - This type of control is the purposeful use of an invasive species’ enemies (predators, parasites, and pathogens) – in other words other exotic species – to reduce the invasive species populations. This option involves much research and testing to be sure the species to be used preys only on the target invasive species.
Although not mentioned as a control measure by the Fish and Wildlife Service, another control method is the consumption of the invasive species as a food source for humans. An article by National Public Radio stated that, until marine predators or parasites learn to feed on invasive lionfish, the best hope for slowing their spread may be humans. The fish are a delicacy in Asia, but not in the Bahamas, given the painful sting their spines can inflict. A few restaurants serve lionfish, and there's an effort to teach Bahamians how to catch and cook them. ( http://www.npr.org/blogs/health/2011/07/07/137674792/in-a-fish-eat-fish-world-order-asian-carp-and-lionfish-to-save-the-rest ).
D. Potential Problems and Public Opinion
No current methods employed in controlling and eradicating invasive animals are entirely successful and many cause stress, trauma and suffering for the animals involved, raising concerns over their humaneness and impacts on animal welfare. There is an underlying tension between the necessity to manage invasive animals and the desire to protect the welfare of individual animals. ( Hidden Victims: Lack of Welfare Protection of Invasive Animals in Australia , Maike Dorn, Alternative Law Journal, http://www.lawsociety.com.au/idc/groups/public/documents/internetyounglawyers/063777.pdf ).
Whether control of invasive species is humane is a matter of opinion, but retired park superintendant Tim J. Setnicka denounced what he called “systematic biologic genocide” in the Channel Islands National Park in California. Setnicka, unknown to the public, authorized the clandestine intermittent killing of problem pigs on Santa Cruz Island by signing a National Environmental Policy Act document called a Categorical Exclusion. Pigs were either individually shot when no one was around, or were trapped first, and shot or knifed in the trap. Because of the National Park Service record of shooting mules, rabbits and pigs, plus The Nature Conservancy’s program of shooting more than 36,000 sheep on their portion of Santa Cruz Island in the 1980s rumors quickly spread in the early 1990s that the Park Service was going to shoot the remaining 9,000 sheep and 30 abandoned horses. “If we could have gotten away with shooting all the sheep and horses, we would have,” Setnicka admitted. Opposition quickly erased thoughts of such action, and they began trapping and transporting.” ( Channel Islands National Park ex-chief hits cruelty of killing “invasive species” , Animal People Online, http://www.animalpeoplenews.org/05/4/tsg.channelIslands4.05.htm ).
Another example of questionable invasive animal control was the shooting of goats by the United States Navy on San Clemente Island. The shootings brought the attention of animal rights groups, and the Navy eventually agreed to transport the goats off the island, where they were able to be adopted. ( Animal Lovers Volunteer Ass’n v. Weinberger , 765 F.2d 937 (C.A.9 (Cal.),1985)). However, not all invasive species are charismatic enough to garner the attention of the public. Other, less popular invasive species can remain at risk of inhumane treatment without laws preventing inhumane control methods.
Similar concerns over control of invasive species have been raised in Australia. In his article, Hidden Victims: Lack of Welfare Protection of Invasive Animals in Australia , http://www.lawsociety.com.au/idc/groups/public/documents/internetyounglawyers/063777.pdf ), author Maike Dorn explains how specific methods of control from Australia have raised concerns and demonstrated the harm to animal welfare that control and eradication of invasive species presents. For example, yellow phosphorous, used to kill pigs, is a potent irritant damaging the gastrointestinal tract and liver and which usually takes two to four days to kill the pigs. Chloropicrin, a gas used for fumigation of rabbit warrens, causing some rabbits to take up to one week to die. While most of the United States invasive species are not mammals and the same extermination systems are not necessarily used, some of the same concerns are relevant in the United States. ( Hidden Victims: Lack of Welfare Protection of Invasive Animals in Australia , http://www.lawsociety.com.au/idc/groups/public/documents/internetyounglawyers/063777.pdf )
Monk parrots in the United States provide an example of how the inhumane methods for reducing invasive species populations can also be some of the least effective methods. The Avian Welfare Resource Center describes lethal control methods as ineffective in solving conflicts with naturalized parrots in the long term. According to the National Pest Control Association, while the strategy of bird removal by trapping and lethal baiting reduces the population it only offers a temporary solution to the problem. Birds will migrate back into the area and reinhabit previous roosting sites if they are not excluded from the site. So in either case for long term bird management, exclusion is essential. Fortunately, there are humane non-lethal solutions that can make an area unattractive to birds, thereby reducing bird presence to an acceptable level. ( Frequently Asked Questions About Monk Parrots , Avian Welfare Resource Center, http://www.avianwelfare.org/issues/forum.htm ).
As the pace of globalization continues to increase, the threat of new species introductions also increases. Human activity such as trade, travel and tourism is likely to continue to increase substantially, increasing the speed and volume of species movement to unprecedented levels. If the spread of invasive species is not prevented, then their presence in United States ecosystems may become irreversible. Action has been taken at both the federal and state level to limit the spread of invasive species.
There tension between managing invasive animals and protecting the welfare of individual animals is apparent from the laws addressing both invasive species control and animal cruelty. Many control methods raise significant animal welfare issues. Invasive species also impact the welfare of native species through competition for resources and predation. Finding a balance amongst the goals of protecting all animals as well as the human environment will be a continuing struggle in United States law.