New Endangered Species Act Rule Narrows "Harm" Definition, Prompting Legal Challenges

Developers, energy producers, miners, timber operators, and landowners who have spent decades treating habitat impacts as a core permitting hurdle may soon face a much easier calculus. On Friday, July 10, the Trump Administration finalized a rule, "Rescinding the Definition of 'Harm' Under the Endangered Species Act," marking a major change in how the Endangered Species Act's (ESA) prohibition on "take" of protected wildlife will apply to habitat modifications and degradations, and effectively narrows the regulation of a causation factor that may, but does not always, result in actual prohibited "take."[1] The move is likely to reduce regulatory burden for development projects that may impact sensitive habitat so long as the projects do not cause actual injury or death to listed species. On Tuesday, July 14, nine environmental advocacy groups filed suit in federal district court in Seattle challenging the rescission of the regulatory definition of "harm" and seeking its reinstatement.

For decades, the Fish and Wildlife Service (FWS) and National Marine Fisheries Service (NMFS) interpreted "harm" to include significant habitat modification or degradation that actually killed or injured listed wildlife by impairing essential behaviors such as breeding, feeding, spawning, migrating, or sheltering. The new rule rejects that approach and removes the definition of "harm" from federal regulations at 50 C.F.R. Parts 17 and 222.

The New Rule

The rule formally removes the regulatory definition of "harm" from both the FWS and NMFS regulations implementing the ESA. The agencies are not replacing the definition with a narrower version. Instead, they state that they will rely directly on the ESA's statutory definition of "take," which prohibits actions such as harassing, pursuing, wounding, killing, trapping, capturing, or collecting protected wildlife.

Under the agencies' new interpretation, habitat modification alone generally will no longer constitute prohibited "take" under ESA Section 9 unless such modification results in direct injury to or killing of protected wildlife. In the final rule, the agencies repeatedly describe prohibited take as involving affirmative acts directed against animals themselves, rather than indirect effects resulting from habitat changes.

The rule applies prospectively only. Existing incidental take permits, habitat conservation plans, conservation agreements, and incidental take statements will remain in place and will not be reevaluated.

How the Rule Impacts Industry

The rule is likely to have substantial implications for ESA permitting and enforcement. Because habitat modification will no longer independently qualify as prohibited "harm," fewer projects may require incidental take permits under Section 10.

The agencies acknowledge that activities such as farming, oil and gas development, mining, logging, and real estate development may face fewer ESA permitting and mitigation obligations where impacts are limited to habitat modification rather than demonstrable direct injury to, or killing of, listed species.

The rule also narrows the basis for habitat conservation plans and related mitigation requirements that were developed around the prior interpretation of "harm." According to the agencies, applicants for incidental take permits will no longer need to analyze habitat modification itself as prohibited take or develop mitigation measures solely to address habitat impacts. This will likely result in significantly smaller habitat mitigation obligations (i.e., smaller habitat conservation obligations) and, for some projects, eliminate the need for any take permits where listed species can be excluded from the project footprint. Conversely, and in addition to relief sought in the lawsuit challenging the rule, projects with habitat impacts may be exposed to additional scrutiny from environmental organizations and opponents for potential citizen suit liability where "direct" harm can be demonstrated.

The rule is part of the Trump administration's broader efforts to streamline project permitting by weakening environmental regulations; in 2025, the Council on Environmental Quality issued an interim final rule removing its regulations implementing the National Environmental Policy Act and the Environmental Protection Agency proposed a rule to narrow the definition of Waters of the United States in the Clean Water Act. The changes to the ESA were also motivated by the Supreme Court decision in Loper Bright v. Raimondo that overturned decades of deference to agencies' statutory interpretations. The Services argue that, after Loper Bright, agencies may no longer rely on interpretations that are merely "permissible"; instead, they must adopt what they view as the "single, best meaning" of the statute. Applying that framework, the rule concludes that the longstanding definition of "harm," which treated significant habitat modification as prohibited "take" under ESA § 9, exceeds "the proper bounds of the statute and asserting power that Congress never actually gave to the executive branch."

The Services also invoke Loper Bright to justify rejecting reliance interests and promulgating no replacement definition. They maintain that continuing to enforce an interpretation they now regard as unlawful would conflict with the executive branch's constitutional duty to "take Care that the Laws be faithfully executed." As a result, the rule rescinds the definition entirely and returns to what the agencies describe as the ESA's plain statutory text.

The final rule will become effective September 8, 2026, absent any interim ruling from the district court.

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Dan Quinley is counsel in DWT's San Francisco office, Olivier Jamin is counsel, Elaine Albrich is a partner and serves as co-chair of the firm's energy, natural resources & environmental practice, and Madeline Marcellino is an associate in the firm's Portland office. DWT's environmental and land use teams are monitoring this rule and the anticipated litigation closely. For questions about how the change may affect your permitting strategy, mitigation obligations, or litigation exposure, please contact the authors or another member of our environmental or land use teams. To stay informed, sign up for our alerts.