Endangered Species Law & Policy

On November 21, 2025, the U.S. Fish & Wildlife Service and National Marine Fisheries Service (collectively, the Services) published several proposed rules to revise their regulations implementing certain provisions of the Endangered Species Act (ESA). To a substantial extent, the Services are proposing to return to the regulations put in place by the first Trump Administration in its prior rulemakings and thereby undo the changes put in place by the Biden Administration. This is the fourth in a series of blog posts that will briefly describe each proposed rule. The notice states the Services will accept comments on the proposed rules until December 22, 2025. A number of stakeholders have asked the Services to extend the comment deadline. As of this time, the Services have not done so.

In the fourth of the proposed rules, the Services propose to revise portions of their regulations implementing the consultation provisions in section 7 of the ESA. Section 7 requires that federal agencies consult with the Service(s) for any federal agency action that “may affect” a listed species or designated critical habitat. Formal consultation results in a biological opinion that determines whether the proposed federal action is likely to jeopardize the continued existence of a listed species or result in destruction or adverse modification of designated critical habitat of such species. If the proposed action is not likely to jeopardize the listed species or result in adverse modification, the Service(s) issue an incidental take statement with reasonable and prudent measures. If the proposed action is likely to jeopardize the listed species or result in adverse modification, the Service(s) issue reasonable and prudent alternatives in addition to an incidental take statement with reasonable and prudent measures. The process the Services undertake in analyzing the effects of the proposed action is often referred to as “effects analysis.”

The Services proposed the following substantive changes to return to their 2019 regulations.

1. Revert to the prior definition of “effects of the action”
2. Revert to the prior definition of “environmental baseline”
3. Revert to the prior definition of “reasonable and prudent measures”
4. Change the regulatory provision regarding formal consultation to conform to the revised definition of “reasonable and prudent measures”
5. Reinstate and elaborate on the provision that provides guideposts for “reasonably certain to occur,” a term that is relied on to define the “effects of the action” and “cumulative effects”

The first two changes above to the definitions of “effects of the action” and “environmental baseline” may be expected to allow the Services to more clearly and efficiently differentiate the effects of the proposed agency action from the environmental baseline when completing an “effects analysis.” This differentiation is critical to determining whether the proposed action—as opposed to myriad other factors that affect the species’ population dynamics—is likely to jeopardize the continued existence of a listed species or result in destruction or adverse modification of designated critical habitat.

The third and fourth changes above are intended to return to the Services’ long-time interpretation of the term “reasonable and prudent measures” and undo the Biden Administration’s effort to authorize the Services to require “mitigation” or “offset” for the effects of incidental take. In the proposed rule, the Services contend that authorizing the Services only to minimize the amount or extent of take (rather than going beyond this and authorizing mitigation of take) by regulation is more faithful to the legislative intent as expressed in ESA section 7(b)(4)(C)(ii).

The final change above is intended “to prevent confusion and provide more clarity in the regulatory text” in light of the importance of the term “reasonably certain to occur” as used in the regulatory definitions of “effects of the action” and “cumulative effects.”