Understanding the Rescission of the ESA Definition of “Harm”

Take Determinations May Shift Away from Habitat Modification Alone

On July 14, 2026 (91 FR 43300), the U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS) finalized the previously proposed rule rescinding the longstanding regulatory definition of harm under the Endangered Species Act (ESA; 16 U.S.C. 1531 et seq.). The final rule is effective September 14, 2026. 

While the rule does not amend the ESA's statutory definition of take, it signals a significant shift in how the USFWS and the NMFS (the Services) may evaluate whether a take occurs. The agencies have indicated that take should be tied more closely to direct, affirmative actions against listed species rather than indirect effects resulting solely from habitat modification or degradation. 

For project proponents with a federal nexus, ESA consultation requirements remain unchanged, but the Services' interpretation of incidental take could change substantially moving forward. We recommend continuing to evaluate habitat modification and ecological effects during ESA analyses, while recognizing that future take determinations and Incidental Take Statements (ITS) may be approached differently by the Services. 

Why the Services Rescinded the Definition

The ESA prohibits the take of endangered species, which Congress defined to include actions such as harassing, harming, pursuing, hunting, killing, trapping, capturing or collecting protected species. However, Congress did not define the term harm. 

In 1981, USFWS adopted a regulatory definition stating that harm could include significant habitat modification or degradation when it results in injury or death to wildlife through impairment of essential behavioral patterns such as breeding, feeding or sheltering (46 FR 54748 at 54750, November 4, 1981). NMFS later adopted a substantially similar definition. 

The Supreme Court upheld that definition of harm in Babbitt v. Sweet Home Chapter of Communities for a Great Oregon, 515 U.S. 687 (1995), relying in part on the principle of judicial deference to agency interpretations established in Chevron U.S.A. Inc. v. NRDC, 467 U.S. 837 (1984). Following the Supreme Court's 2024 decision in Loper Bright Enterprises v. Raimondo, 144 U.S. 2244, which eliminated Chevron deference to agencies' interpretation, the Services revisited the regulation and concluded the existing definition of harm did not represent the “single, best reading of the statute.”

New Focus on Direct Take

Although the final rule simply removes the regulatory definition without replacing it, the final rule’s background and responses to public comments provide insight into the Services' future interpretation of harm and overall implementation of take.

The Services appear to be aligning more closely with the dissenting opinion in Babbitt v. Sweet Home, which viewed take as requiring an affirmative action directed at individual animals rather than actions that only indirectly cause injury to a population of animals through habitat changes. 

Under this approach:

• Habitat modification alone may be less likely to support a finding of take when listed species are not present.
• Greater emphasis may be placed on direct interactions with individual animals.
• Activities capable of directly injuring or killing listed species will continue to warrant careful evaluation.
• The Services will likely rely on ESA Section 4 (designation of critical habitat), ESA Section 5 (land acquisitions), and voluntary conservation with willing landowners to address endangered species habitat considerations.
   

Consultation Requirements Are Not Changing

Despite the significance of the rule, several key ESA requirements remain intact.

Federal agencies or projects with a federal nexus must still comply with ESA Section 7(a)(2) consultation requirements. Project proponents should continue to assess how proposed activities affect listed species and their critical habitats during formal or informal consultation. 

In practical terms, we recommend project proponents continue to analyze whether modifications or alterations to habitat will affect listed species through established ecological pathways and continue to incorporate those analyses into the Effects of the Action in Biological Assessments under formal consultations or in the analysis of effects under informal consultations.

The rule also does not apply retroactively. Consultations that have already concluded will neither change nor be reopened, even if habitat was considered as part of the analysis.

Potential Implications for Incidental Take

The most immediate effects may emerge during the Services' evaluation of incidental take.

Historically, habitat loss or degradation has sometimes been used as a basis for estimating or characterizing incidental take. The agencies may now adopt a narrower interpretation that relies more heavily on evidence of direct impacts on individual animals. 

Examples of activities that could still result in incidental take include construction or equipment operations that directly injure, crush, or bury listed species. 

Conversely, habitat impacts occurring when a species is absent from an area may become less likely to result in a take finding. Potential examples could include:

• Seasonal bat roosting or pup-rearing habitat when listed bats are occupying hibernacula elsewhere.
• Stopover habitat for migratory bird species when individuals are not present.
• Spawning habitat modifications when listed fish are not actively using the habitat.
   

What to Do Now

The rescission of the ESA regulatory definition of harm does not eliminate ESA consultation requirements or the need to evaluate critical habitat effects. However, it may substantially change how USFWS and NMFS determine whether incidental take occurs and when an ITS or Incidental Take Permit is necessary. 

Several lawsuits have already been filed challenging the final rule, and if an injunction is issued, the prior definition could remain in place pending case resolution. Until additional guidance and court decisions provide greater clarity, we recommend continuing to conduct species and habitat effects analyses while recognizing that the Services may increasingly focus take determinations on direct impacts to listed species rather than habitat modification alone. 

Have a specific question or need additional guidance? Contact or connect with Michael.Mayer [at] hdrinc.com (Mike Mayer) (LinkedIn) or Erin.Hatchett [at] hdrinc.com (Erin Hatchett) (LinkedIn).