Sadie Jacobs

Animal Welfare Considerations in Invasive Species Management

This piece was written for Lewis & Clark’s Emerging Topics in Animal Law course. All views expressed are those of the author.

By Sadie Jacobs

Invasive species often are introduced to new areas as “unintended hitchhikers on cargo ships and other vehicles,” and can devastate “plant and animal communities on our farms, ranches and coasts; and in our parks, waters, forests, and backyards.”[1] Invasive species are a concern both economically and ecologically, but methods used to eradicate invasive animal species frequently raise welfare concerns; many of the methods used can cause pain and suffering for the animals involved. Therefore, balancing invasive species management along with animal welfare can be extremely difficult.

  1. Introduction

As per Executive Order 13112[2] invasive species are plants, animals, or pathogens that are (1) non-native (or alien) to the ecosystem under consideration, and (2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.[3] There are currently an estimated 6,500 or so invasive species in the United States, and their effects are broad: invasive species can decimate crops, clog water facilities and waterways, transmit wildlife and human diseases, threaten fisheries, and increase fire vulnerability.[4]

Invasive species are primarily spread through human activities, and increased global trade and travel has exacerbated this problem.[5] For instance, ships can carry aquatic organisms in their ballast water or on their propellers, insects can bore into wooden shipping palettes and crates, ornamental plants can escape from gardens and nurseries into the wild, and some pets are intentionally or accidentally released into the wild.[6]

  1. Ecological and Economic Effects of Invasive Species

Invasive species can cause a multitude of ecological and economic issues. For example, when a new species is introduced into an ecosystem, it may not have any natural predators or other controls. The new species can then reproduce and disperse quickly, outcompeting native species for food or other resources.[7] Similarly, other native species may not have evolved defenses against the invader and thus can be highly susceptible to predation.[8] And invasive species can also transmit diseases to new areas.[9]

There are more indirect threats from invasive species too. Invasive species can change the food web in an ecosystem by destroying or replacing native food sources.[10] Additionally, the invasive species themselves may provide little to no food value for other species. And particularly aggressive invasive plant species, like kudzu, can quickly replace a diverse ecosystem with a monoculture.[11] Finally, some invasive species are capable of changing the abiotic conditions in an ecosystem, such as the soil chemistry or intensity of wildfires.[12]

To make matters worse, the effects from invasive species can also interact with climate change. For example, the effects from mountain pine beetles in western states can be exacerbated by climate change, with the beetles taking advantage of drought-weakened plants and leading to even greater risks of forest fires.[13]

  1. Legal Issues

While no one law addresses all the concerns generated by invasive species, many federal laws address some aspect of their management.[14] These laws date as far back as the Lacey Act in 1900, which has a provision addressing injurious species (animals that injure the interests of human beings and wildlife).[15] Another law is the Nonindigenous Aquatic Nuisance Prevention and Control Act, passed in 1990.[16] This Act created a Task Force to control aquatic invasive species. More recently, Congress decided to respond to specific invasive species threatening the Great Lakes ecosystem; the Asian Carp Prevention and Control Act is intended to prohibit the importation and shipment of certain carp species.[17]

In 1999, President Clinton recognized that invasive species are one of the most serious threats to biodiversity when he passed Executive Order 13112. Executive Order 13112 defines “invasive species” as an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.[18] The order was signed in response to the over $123 billion in damage that was estimated to have been done annually in the United States by species such as zebra mussels and brown tree snakes, which shut down electrical utilities and caused power outages,[19] and sea lampreys, which caused the collapse of lake trout and other Great Lakes fisheries.[20]

States have also enacted legislation in order to combat the introduction and spread of invasive species. Nineteen states now have invasive species councils or similar bodies. However, state laws mostly focus mainly on invasive plant species, rather than animals.[21]

  1. Animal Welfare Considerations

While the goals of federal and state laws often focus on the control or eradication of invasive species and the protection of native biodiversity, there are inherent concerns over the methods used and their impact on the invasive animals themselves. Current methods employed in controlling and eradicating invasive animals frequently are not entirely successful and many cause stress, trauma, and suffering for the animals involved, which can impact animal welfare.

There is inherent tension between controlling invasive species and animal welfare. Almost every state has a law prohibiting cruelty to animals.[22] And while the laws typically do not explicitly mention invasive species, many do reference pests.[23] Many of the laws have exemptions for species considered as pests, impliedly allowing these animals to be killed inhumanely. For example, while there is some disagreement in the scientific and wildlife management communities as to whether coyotes are technically considered invasive, at the very least many states consider them to be pests and consequently lower or essentially ignore any welfare concerns in their management.[24] Specifically, coyote killing contests are currently legal in more than 40 states, sometimes subjecting the animals to attempted control through killing competitions.[25] During these competitions, there are little to no rules as to how the animals can be killed, which results in horrific treatment for more than half a million animals per year.[26], [27]

The 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, and yet invasive species also impact the welfare of native species through competition for resources and predation. Finding a balance amongst the goals of protecting the welfare of all animals as well as maintaining the human environment will be a continuing struggle in United States law.

  1. Future Directions

Most species that are considered invasive were taken from their native ranges. These animals are now invasive by no fault of their own; they are trying to survive just like other living beings and therefore, it is vital that we act with more compassion when considering invasive species management. Competing values create ethical dilemmas and disagreements, and there is no single right answer determining how to manage invasive species. For instance, there are conflicts between sustaining certain human livelihoods and preserving a particular species, or between the protection of native ecosystems and overall animal welfare.

Invasive species management generates ethical disagreements and dilemmas in which the sometimes competing interests among humans, animals, and the environment, all need to be part of the discussion. The way in which these different values are prioritized will determine policy. Explicit consideration of the values at stake should underpin careful debate about, for instance, whether constant human involvement in nature reserves and other wild areas is desirable, and what constitutes “good” and “bad” human interventions in relation to wildlife.

Control operations that fail to effectively manage invasive species may have high costs and little benefit.[28] Such failures may mean that “tens to thousands of the target pests have been killed without achieving the goal of the operation and, in the worst case where there is no further management of the pest species, those animals have died to no good purpose, or at best for a temporary reduction of their impacts.”[29] Coyotes are a prime example yet again — for all the efforts made to “control” them, they continue to spread across North America. In fact, research shows that coyote populations respond to control methods by reproducing more.[30]

Animal advocacy groups such as People for the Ethical Treatment of Animals have tried to highlight welfare issues with the control of some invasive species, such as with Burmese pythons in Florida. The Florida Fish and Wildlife Conservation Commission is responsible for managing these animals and oftentimes their methods are unnecessarily cruel. For instance, recently, a record-breaking python for its size was caught and shot three times, when one shot would have sufficed.[31]

Every invasive species presents unique management challenges, so there is no single solution available to the management and welfare dilemma. And the current methods to control invasive species certainly highlight the welfare and ethical issues at hand. However, there are a variety of non-lethal control methods successfully used for managing predators like coyotes, such as fencing, fladry/turbo fladry, livestock guardian angels, night corrals and shed lambing, scare tactics and foxlights, and animal husbandry and shepherding.[32] And many of us are familiar with spay and neuter programs for feral cats, even though we often do not consider them to be an invasive species.[33] In addition, wild horses, currently managed by the Bureau of Land Management (“BLM”), have been sold for slaughter by people being paid up to $1,000 an animal by the BLM to adopt them.[34] Thus, to ensure that animal welfare concerns are at least addressed, state anti-cruelty laws could be improved to permit broader consideration of invasive or pest species.

Invasive species are undoubtedly damaging ecosystems and native animals, and the welfare of these native animals also needs to be considered. For example, in the United States alone, outdoor cats — including feral cats — kill approximately 2.4 billion birds every year.[35] But the invasive animals should be treated with respect and dignity. There often is little compassion involved when it comes to managing invasive species, but if we add compassion to the best available science, we should be able to create more robust standards and regulations to improve the welfare of the likely millions of animals considered to be invasive in the United States.


[1] Cassandra Burdyshaw, Brief Summary of Invasive Species and the Law, Animal Legal & Historical Center, (last visited Sep. 24, 2021).

[2] This 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, while the Committee is a group of non-federal experts and stakeholders. Together, they formulated an action plan for the nation.

[3] What are Invasive Species?, United States Department of Agriculture National Invasive Species Information Center, (last visited Oct. 28, 2021).

[4] What is an Invasive Species?, United States Geological Survey, (last visited Oct. 28, 2021).

[5] Invasive Species, National Wildlife Federation, (last visited Nov. 14, 2021).

[6] Supra note 5.

[7] Hong Liu & Peter Stiling, Testing the Enemy Release Hypothesis: A Review and Meta-Analysis, 8 Biol. Invasions 1535 (2006).

[8] Supra note 5.

[9] Invasive Pathogens, United States Geological Survey Invasive Species Program, (last visited Nov. 27, 2021).

[10] Supra note 5.

[11] Kudzu, Center for Invasive Species and Ecosystem Health, (last visited Dec. 1, 2021).

[12] Id.

[13] Michael J. Jenkins et al., Interactions among the Mountain Pine Beetle, Fires, and Fuels, 60 Forest Sci. 489 (2014).

[14] Cassandra Burdyshaw, Detailed Discussion of the Laws Concerning Invasive Species, Animal Legal & Historical Center, (last visited Dec. 1, 2021).

[15] Id.

[16] Id.

[17] Id.

[18] Supra note 5.

[19] Invasive Species, National Geographic, (last visited Oct. 25, 2021).

[20] Id.

[21] Supra note 14.

[22] Id.

[23] Twenty-two states have some form of an exemption relating to pests. Some states broadly exempt pest species, and some exempt the poisoning of pest species by property owners. At least one state, Vermont, allows the destruction of pests by a property owner to be used as an affirmative defense. Supra note 14.

[24] The Hidden War on Wildlife: Killing Contests in North America, Project Coyote, (last visited Nov. 14, 2021).

[25] Supra note 14.

[26] Id.

[27] Austa Somvichian-Clausen, The Controversy Over Wildlife Killing Contests, The Hill, (last visited Dec. 1, 2021).

[28] Cowan P. Warburton et al., Welfare and Ethical Issues in Invasive Species Management, 432 8th European Vertebrate Management Conference 44 (2011).

[29] Id.

[30] Matthew E. Gompper, The Ecology of Northeast Coyotes: Current Knowledge and Priorities for Future Research, WCS Working Paper No. 17 (2002).

[31] New PETA Statement re Ramped-Up ‘War on Pythons,’ People for the Ethical Treatment of Animals, (last visited Nov. 14, 2021).

[32] Nonlethal Solutions to Reduce Conflicts, Project Coyote, (last visited Dec. 5, 2021).

[33] Western Governors’ Association’s Misguided Inclusion of Feral Cats on Its List of Invasive Species, Best Friends Animal Society, (last visited Dec. 1, 2021).

[34] Dennis Webb, BLM Seeks to Stop Slaughter of Wild Horses, The Grand Junction Daily Sentinel, (last visited Dec. 1, 2021).

[35] Cats and Birds, American Bird Conservancy, (last visited Dec. 1, 2021).


Sadie Jacobs