Preservation Proposals: The Effects of Rollbacks on the Endangered Species Act

By: Hannah Nolton.

Brief Introduction

The Endangered Species Act (“ESA”) has protected Earth’s most vulnerable species since its enactment in 1973. Now, fifty-three years later, its protective measures are changing. Before the change proposed on July 10, 2026, the ESA prohibited “taking” wildlife, which means “to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct” (emphasis added). The U.S. Fish and Wildlife Service further defined harm—mentioned in the definition of “take”—as any act that actually kills or injures wildlife which “may include significant habitat modification or degradation where it actually kills or injures wildlife by significantly impairing essential behavioral patterns, including breeding, feeding, or sheltering.” 

Recently, the Trump Administration proposed the removal of “habitat modification” from the definition of “harm.” The Administration argues that the current definition of harm runs contrary to the meaning of “take” as interpreted in the ESA. This is because the definition does not match the single, best meaning of the statute, and violates the noscitur a sociis canon of construction, which determines the meaning of an ambiguous word through its associated words in context. Quotes from Justice Scalia’s dissent in the case Babbitt v. Sweet Home Chapter of Communities for a Great Oregon bolster the Administration’s position, saying, “[t]o ‘take,’ when applied to wild animals, means to reduce those animals, by killing or capturing, to human control,” and that harm should be “construed to require an ‘affirmative act[] . . . directed immediately and intentionally against a particular animal–not [an] act[] or omission[] that indirectly and accidentally cause[s] injury to a population of animals.” Ultimately, the majority decided the opposite, reasoning that, based on public policy and Congress’s intent, the definition of “harm” should include “significant habitat modification or degradation that actually kills or injures wildlife.” While Scalia’s dissent is not binding precedent, the Administration’s proposed change seems to agree with his reasoning, interpreting “harm” as only that which directly and intentionally kills or injures an animal.

What Will the Omission Do?

The Administration claims that the removal of “habitat modification” from the statutory definition of harm will better fit the definition of “take” and the overall purpose of the ESA. But, they may not have fully considered the effects this change could have on ecologies across the United States. Most endangered species are on the designated list because there is nowhere else for them to live, with their habitats being paved, burned, or otherwise destroyed. Studies have shown that, of the species listed as “endangered” between 1975 and 2017, direct killing primarily threatened only seventeen percent.Whereas eighty-one percent of those species were listed due to habitat loss and degradation. An animal’s habitat allows them to find food, hide from predators, and do whatever they need to survive. Destroying an animal’s habitat makes simple survival tasks impossible. 

Congress wrote the ESA with the purpose of providing “a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved and [providing] a program for the conservation of such endangered species and threatened species.” Thus, the new rule directly contradicts the goals that Congress set out to achieve in 1973. When people can legally modify habitats without protecting the species living there (for example, logging), protecting endangered species through ecosystem conservation becomes more difficult. 

Essentially, Courts—not agencies—will determine what harm actually means after this change. Stanford environmental law scholar Deborah Sivas explains how, “[i]n essence, the federal regulators have opened the door for developers and landowners to destroy habitat suitable for listed species without needing to get a ‘take’ permit.” Instead of the agency deciding which companies and activities can safely do business in certain habitats, courts will have to determine which activities “directly” injure animals in a way that falls within the new definition of “harm.” It is not clear how and when this dispute may be resolved, but the boundaries of this new interpretation will likely be settled in court. In the meantime, the habitats of animals on the endangered species list will likely be carelessly modified, thus destroying the small populations of these species the United States currently fosters. Some examples of species whose populations are declining because of habitat modifications (though not through direct killing or injuring) include the ocelot threatened by border-wall construction, and the Northern Spotted Owl and gray wolf which depend on forests that are being rapidly deforested to survive. The extinction of one species due to habitat loss affects an entire ecosystem. For example, if the ocelot were to disappear in Texas, rodent control would also disappear. Thus, conserving endangered species is essential to maintaining fragile ecosystems around the world.   

How Will the Omission Affect Arizona?

The Sonoran Desert is one of the most biologically diverse deserts in North America, yet it is not immune to biodiversity loss. The effects described in Part II will also occur in Arizona, especially if the proposed definition encourages greater development at the expense of habitats. Phoenix and the surrounding areas are growing at seemingly unprecedented rates. If one drives out of Downtown Phoenix to the desert surrounding it, they notice endless advertisements for incoming housing developments. With this new definition of “harm,” more careless and quick development will likely occur until courts decide what constitutes “harm” under the ESA. This may cause a quick and efficient mass destruction of biodiversity in the Sonoran Desert, as more developers capitalize on the ever-growing market. Biodiversity is a powerhouse defense against climate change. It can help provide clean water, clean air, and even slow the spread of infectious zoonotic disease. Conservation is one way in which we can preserve biodiversity and it is a crucial legal conversation, especially in one of the most biologically diverse areas of North America.

Many believe that the definition of harm in the ESA needs to include habitat modification and destruction to preserve endangered species, and thus biodiversity. Still, the modified definition took effect on September 14, 2026. Environmental non-profits have filed suit against the U.S. Fish and Wildlife Service and NOAA Fisheries to contest the change. While it is too early to understand the true effects the change will have on endangered species, it is an issue that legal and scientific professionals will continue to follow. Without knowledge on how the change would affect the relationship between development and biodiversity across the United States, a new proposal was made on September 14, 2026. This directive—issued the same day the Administration implemented the change to the harm definition—may allow courts to consider any activity that accidentally kills an endangered species a legal activity. This cements the interpretation of harm from the change, where accidentally killing an endangered species by doing something like cutting down a tree will no longer be illegal. Only time will tell what the new definition of “harm” will truly be, but until then, the modification of endangered species habitats will continue to occur and perhaps threaten this country’s incredible biodiversity.