A December 2020 final rule defining “habitat” could have important consequences for future designations of lands and waters as “critical habitat” under the Endangered Species Act (ESA). Designation of critical habitat by the U.S. Fish and Wildlife Service or National Marine Fisheries Service (jointly, the “Services”) can affect projects that require federal agency permits or funding, because ESA section 7 requires federal agencies to ensure through consultation with the Services that their actions are not likely to adversely modify or destroy designated critical habitat.

On December 16, 2020, the Services adopted, for the first time, a regulatory definition of habitat, as follows:

For the purposes of designating critical habitat only, habitat is the abiotic and biotic setting that currently or periodically contains the resources and conditions necessary to support one or more life processes of a species.

85 Fed. Reg. 81,411 (Dec. 16, 2020) (to be codified at 50 C.F.R. § 424.02). This definition will become effective January 15, 2021 and will apply to proposals by the Services to designate areas as critical habitat after January 15. The Services do not intend to reevaluate any prior critical habitat designations on the basis of this rule.

The final definition responds to the US Supreme Court’s November 27, 2018, unanimous decision in Weyerhaeuser Co. v. U.S. Fish & Wildlife Service, 139 S. Ct. 361 (2018), which held an area is eligible for designation as critical habitat under the ESA only if the area is actually habitat for that species. For additional background on Weyerhaeuser Co. and the Services’ initial efforts to address Weyerhaeuser, including the Services’ proposed definition of habitat, see our September 16, 2020 blog post .

In response to comments on the Services’ proposal and upon further consideration, the Services’ final definition modifies the proposed definition and proposed alternative definition and further clarifies the regulatory scope of habitat. The key aspects of the final definition include the following:

• Introductory Phrase. The Services added the introductory phrase: ‘‘For the purposes of designating critical habitat only,’’ to explicitly limit the definition’s applicability to the designation of critical habitat. This clarification is intended to address concerns about the potential for the definition to apply to other sections of the ESA or other federal programs that use the term “habitat.”

• “Abiotic and Biotic Setting.” The Services replaced the proposal’s phrase “physical places” with “abiotic and biotic setting” to capture a broader set of characteristics, conditions, and processes (i.e., habitat is more than simply a physical location), and to address concerns that natural spatial and temporal variations in habitat were not encompassed in the proposed definition. Abiotic refers to non-living characteristics such as soil, water, temperature, or physical processes. Biotic refers to living features such as specific plant communities or prey species. The Services chose not to use the ESA’s statutory phrase “physical or biological features” to avoid overlap between statutory language regarding occupied critical habitat and this broader regulatory definition. The use of “abiotic and biotic setting” is also intended to avoid using the undefined term “attributes” from the Services’ proposal, but it is intended to be inclusive of “physical or biological features.”

• “Currently or Periodically.” The Services included “periodically,” in the final definition, to clarify that habitat includes ephemeral habitat – areas that may be variable both temporally and spatially, such as areas prone to seasonal flooding and dynamic riverine sandbars that may develop during certain times of the year. In other words, these are areas where the resources and conditions are not consistently present, but appear at regular intervals. The definition, therefore, excludes areas that do not currently or periodically contain the requisite resources and conditions, even if they could in the future after restoration activities or other changes.

• “Resources or Conditions.” The final rule replaces the phrase “existing attributes” in the proposal, which the Services state was found to be vague, poorly defined, or confusing by commenters, with “resources or conditions.” This phrase clarifies that the habitat definition includes all qualities of an area that can make that area important to the species, such as dynamic processes (e.g., riverine sand bar formation or fire disturbance), a set of environmental conditions (e.g., temperature, pH, and salinity), or any characteristics that can satisfy life-history needs (e.g., food, shelter).

• “Necessary to Support.” The Services’ proposal solicited comments on the phrases “depend upon to carry out” and “use to carry out” one or more life processes and which phrase better describes the relationship between species and their habitat. Commenters offered criticisms of both phrases. Thus, instead, the Services decided to use the phrase “necessary to support.” The Services note that this phrase is intended to convey its common meaning and better demonstrates how the habitat definition includes areas that would qualify as occupied and unoccupied critical habitat.

• “One or More Life Processes.” The phrase “one or more life processes” includes areas used only during particular seasons (e.g., for migratory species) or phases in the species’ life cycle (e.g., as fresh-water spawning habitat). This phrase is intended to have the common biological meaning, including a series of functions such as movement, respiration, growth, reproduction, excretion and nutrition that are essential to sustain a living being.

• Unoccupied Areas. The definition is broad enough to include currently unoccupied areas that meet the definition of “critical habitat.” For example, an area where a species has been extirpated may nonetheless provide the abiotic and biotic setting that currently or periodically contains the resources and conditions necessary to support one or more life processes of a species.

Overall, the Services state that the rule is intended to help clarify what features will be considered habitat for a species when considering the potential designation of critical habitat for that species.