Habitat Protection Matters for Species Conservation

Do you have to kill an endangered animal to violate the Endangered Species Act (ESA)—or is destroying its home enough?

The ESA prohibits the “take” of an endangered species without authorization. The Act defines “take” to mean, “harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect.”

The U.S. Fish and Wildlife Service (FWS) has long defined “harm” to include acts that “actually kill or injure wildlife,” including significant habitat modification or degradation that impairs essential behaviors such as breeding, feeding, or sheltering. This definition reflects the reality that habitat loss threatens species survival.

The U.S. Supreme Court upheld this interpretation, rejecting the argument that take liability requires direct physical contact with animals. The Court emphasized that habitat modification can foreseeably cause injury or death when it disrupts the conditions species need to survive. Even if a bulldozer never touches an animal, a project may still amount to “harm” if habitat alteration impairs essential behavioral patterns.

The definition of harm carries significant implications for Section 9 of the ESA, which applies to private parties. Under current law, a private developer can violate the ESA by modifying any habitat used by a listed species—not just designated “critical habitat”—if that modification actually kills or injures wildlife by impairing essential behaviors.

“Harm” also plays a role under Section 7 of the ESA, which governs federal agency actions. When a project involves federal funding, permitting, or approval, agencies must consult to ensure that the action is not likely to jeopardize listed species, or destroy or adversely modify designated critical habitat. A broader definition of harm increases the likelihood that consultation is required and that agencies must consider habitat impacts at the planning stage.

In April 2025, FWS and the National Marine Fisheries Service proposed rescinding the regulatory definition of “harm.” The agencies argued that including habitat modification stretches the statutory meaning of “take” beyond its best interpretation, and that rescission would align with the ESA’s “single, best meaning.”

If finalized, the change would constrain the law’s ability to treat habitat destruction as a prohibited take. Without this route, take liability would require harder-to-prove showings of direct injury or death of individual animals.

This proposal has drawn criticism from legal scholars and conservationists, who argue that habitat modification poses a major harm to endangered and threatened species. They warn that removing habitat modification as a form of harm will have adverse consequences on protected species.

Even so, the ESA would not lose all its power. Section 7 would continue to regulate federal actions through consultation requirements, and Section 9 would still prohibit direct killing or injury of listed species. States and local governments also have supplementary laws. These measures provide some protection, but whether these measures are enough remains to be seen.

In this week’s Saturday Seminar, scholars evaluate ongoing efforts to protect endangered and threatened species.

• Accepting the Fish and Wildlife Service’s proposal to remove the regulatory definition of “harm” from the ESA would undermine habitat protections and contradict the text of the statute, argues Jessica R. Graham of Harvard Law School in an article in Ecology Law Quarterly. Graham explains that the Supreme Court already upheld a regulatory definition of “harm” that includes damage to an animal’s habitat that leads to the animal’s injury or death. Graham maintains that this definition reflects Congress’ intent to afford species with broad protections. Graham contends that narrowing the meaning of “harm” would weaken enforcement of the statute, leading to serious harm to ecosystems and the tribal communities that rely on them.
• Eric Biber of the University of California, Berkeley, in an article in the Michigan Journal of Environmental & Administrative Law, proposes using general permits to regulate greenhouse gas emissions under the ESA. Under Biber’s proposal, the Fish and Wildlife Service would calculate a per-unit fee on greenhouse gas emissions based on estimated species recovery costs. Then, Biber explains, a party initiating a project expected to emit greenhouse gases will pay a compensatory mitigation fee based on the quantity of emissions produced, with the resulting revenue funding species conservation efforts. Biber contends that because general permits apply broadly, this solution would carry low administrative burdens and compliance costs while contributing a meaningful sum to endangered species recovery work.
• In a forthcoming article in the Utah Law Review, Natalie Jacewicz of the University of San Diego School of Law argues that U.S. environmental law overlooks sharp declines in the number of wild animals when species are not at risk of extinction. Jacewicz explains that most environmental statutes prioritize preventing species extinction and therefore fail to address dramatic population losses among “common” animals. This regulatory blind spot undermines the purposes of federal laws that implicitly value abundant wildlife for ecological, economic, and cultural reasons, Jacewicz contends. Jacewicz proposes reforms that would require agencies to monitor and mitigate declining animal abundance through permitting decisions and land-use planning, rather than waiting until species near extinction.
• The ESA provides tools for regulating conservation by genetic engineering, contends John A. Erwin of the University of Florida Levin College of Law in an article in the Cornell Law Review. Erwin explains that special permits for recovery work, including the Controlled Propagation regulations, the 10(j) experimental population procedures, and the special 4(d) rules, which tailor protections for threatened species, can enable regulatory oversight of the creation and release of genetically modified individuals. Erwin argues that, taken together, these tools can allow the careful use of gene editing to aid in conservation while assessing associated ecological and genetic risks. Erwin recommends that ESA regulators take a holistic approach that incorporates broader ecological and cultural concerns into their decisionmaking.
• Incidental take authorizations (ITAs)—which allow otherwise lawful activities to proceed while authorizing limited, incidental harm to protected species—undermine marine mammal conservation in their current form, argue Alexander Carbaugh-Rutland, Jessica Owley, and Kenneth Broad of the University of Miami in an article in the Stanford Environmental Law Journal. Carbaugh-Rutland, Owley, and Broad explain that Congress added ITAs to the ESA after its enactment to ensure wildlife protection would not hinder economic growth. Although ITAs must not jeopardize species’ long-term survival, the authors contend that growing numbers of authorizations, combined with inadequate consideration of cumulative impacts, risk excessive taking. Carbaugh-Rutland, Owley, and Broad recommend that the Services should diversify both authorized actions and mitigation approaches.
• In an article published in the Harvard Environmental Law Review, Jaclyn Lopez of Stetson University College of Law examines how federal wildlife regulators can respond to climate-driven habitat loss. Lopez explains that sea-level rises and coastal development trap many endangered species in shrinking habitats, a problem known as “coastal squeeze.” Lopez argues that the Fish and Wildlife Service has authority under the Endangered Species Act to address this risk by facilitating “assisted migration,” which involves helping species move to safer areas. Lopez points to recovery planning, critical habitat designation, and experimental populations as ways to support migration and reduce climate-related extinctions.