Federal Agencies Propose Rescission of “Harm” Definition Under Endangered Species Act

On April 17, 2025, the U.S. Fish and Wildlife Service (USFWS) and the National Marine Fisheries Service (NMFS) (collectively, the Services) published a proposed rule in the Federal Register to rescind their respective regulatory definitions of the term “harm” under the federal Endangered Species Act (ESA). The proposal would eliminate language that explicitly includes “significant habitat modification or degradation” as a form of prohibited “take” when it “actually kills or injures wildlife.”

The proposed rule reflects a broader shift in federal environmental policy under the new Administration in Washington, D.C. — a trend also evident in recent efforts to scale back federal agency authority under the National Environmental Protection Act (NEPA) (as we summarized here) and in other recent Executive Branch actions.

Why “Harm” Matters: Habitat Impacts and ESA Liability

Under the ESA, it is unlawful to “take” an endangered or threatened species. “Take” is defined broadly in the statute to include “harass, harm, pursue, hunt, shoot, wound, kill, trap, capture or attempt to engage in any such conduct.” Since 1975, the Services’ regulations have interpreted “harm” — a subset of “take” — to include significant habitat modification that kills or injures a listed species by impairing essential behaviors such as breeding, feeding, or sheltering.

This regulatory definition has had sweeping implications for project development. Habitat disturbance — even absent direct contact with individual animals — has often triggered federal “incidental take” permitting and mitigation requirements. In this way, the “harm” definition has functioned as a cornerstone of ESA compliance in habitat-sensitive areas.

The Legal Framework and Basis for the Proposed Change

The Services’ longstanding regulatory definition of “harm” was upheld by the U.S. Supreme Court in Babbitt v. Sweet Home Chapter of Communities for a Great Oregon, 515 U.S. 687 (1995), which applied then-prevailing Chevron deference to agency interpretations. The Court recognized that habitat alteration, when it foreseeably results in injury or death to listed species, can constitute prohibited “take.” (However, in Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024), the U.S. Supreme Court eliminated Chevron deference and held that courts — not federal agencies — are responsible for resolving statutory ambiguities (analyzed in our prior client alert here).)

In the proposed rule, the Services indicate that the regulatory definition — originally adopted by USFWS in 1981 and NMFS in 1999 — exceeds the statutory language of the ESA, which does not itself define “harm.” The proposed rule frames rescission as a return to the “plain meaning” of the statute.

Practical Implications for Developers

If finalized, the proposed rule would remove the regulatory definition of “harm” entirely from 50 C.F.R. § 17.3 (USFWS) and 50 C.F.R. § 222.102 (NMFS), without replacement. This shift marks a substantial departure from longstanding practice, particularly for projects involving habitat disturbance in areas known to support listed species. The change could result in the following:

• Narrower Federal Enforcement

The Services’ proposal suggests a more limited interpretation of “take” — focused on direct injury or mortality — potentially reducing enforcement risk for projects that alter habitat (i.e., through grading, vegetation removal, or streambed alteration) without directly harming listed species. However, case-by-case interpretation may lead to inconsistent enforcement across regions, and litigation is anticipated from environmental groups.

• Reduced Need for Incidental Take Permits (ITPs)

The narrowed scope of “harm” may decrease the number of projects for which federal ITPs and mitigation plans are pursued. In the absence of a binding definition, informal guidance and internal agency policy may increasingly shape how the Services assess potential take. The potential implications of this are two-fold. First, for projects requiring a federal permit — and thus triggering consultation under Section 7 of the ESA — the Services will retain discretion as to whether an ITP is warranted, and outcomes may vary depending on how they interpret project-specific impacts. Second, projects without a federal “trigger” may face even greater uncertainty, as developers must independently assess whether seeking an ITP is a prudent strategy for managing potential ESA liability tied to habitat-related effects.

• Limited Effect in California

Notably, the California Endangered Species Act (CESA) does not prohibit habitat modification unless it results in the direct death or physical injury of a listed species. The California Supreme Court expressly rejected the broader federal interpretation (EPIC v. Cal Fire, 44 Cal.4th 459 (2008)). Nonetheless, developers in California must continue to comply with CESA (for state-listed species), the California Environmental Quality Act (CEQA), and other state and local environmental requirements, which often functionally regulate habitat loss even absent a federal ESA “take.”

• Broader ESA Rollbacks May Follow

As reported by multiple outlets, this rule is part of a broader deregulatory effort to unwind ESA policies adopted under previous administrations. Proposals to revise Section 7 consultation requirements and critical habitat protections are reportedly forthcoming.

What’s Next? Public Comment and Monitoring

Public comments on the proposed rule are due by June 17, 2025. The Services have indicated that they will consider public input before finalizing the rule. If finalized, the rule could materially change how federal ESA compliance is evaluated for projects that alter habitat, particularly those outside of traditional “take” enforcement contexts.

Allen Matkins will continue to monitor this rulemaking and related developments. For more information about how this proposed rule may impact your projects — or to discuss ESA permitting strategies in light of these changes — please contact a member of our Natural Resources and Land Use team.