Services Propose Definition of Habitat for ESA Regulations
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Services Propose Definition of Habitat for ESA Regulations
Categories: Endangered Species

Determining which areas constitute habitat for listed species has important consequences under the Endangered Species Act (“ESA” or “Act”), yet “habitat” is not currently defined by the Act or its implementing regulations.  On August 5, 2020, the US Fish and Wildlife Service and the National Marine Fisheries Service (jointly, “the Services”) proposed a rule to define “habitat” for purposes of designating “critical habitat” under section 4 of the Endangered Species Act.  See 85 Fed. Reg. 47,333 (Aug. 5, 2020).  The Services’ proposal responds to the Supreme Court’s November 27, 2018, unanimous holding in Weyerhaeuser Co. v. U.S. Fish & Wildlife Service, 139 S. Ct. 361 (2018), that an area is eligible for designation as critical habitat under the ESA only if the area is actually habitat for that species.  Accordingly, a final rule defining “habitat” would determine which areas of land and water are eligible for designation as critical habitat.  Such designations can affect projects that require federal agency permits or funding, because ESA section 7 consultation requires federal agencies to ensure that their actions are not likely to adversely modify or destroy designated critical habitat.  The result for federally approved or funded projects can be increased permitting costs and risks, and longer timelines.  The proposal’s comment period ended on September 4.  Over 160,000 comments were submitted.  Stakeholders now await a final rule.


When enacted in 1973, the ESA provided for the listing and protection of threatened and endangered species, but included no requirement or process to designate critical habitat.  In 1978, Congress amended the ESA to require, “to the maximum extent prudent,” that the Services “specify any habitat … considered to be critical” at the time they propose to list a species.  16 U.S.C. § 1533(a)(3)(A).  Congress required the Services to consider non-biological factors, including economic, national security, and other effects of designation, before “specifying any particular area as critical habitat.”  Id. § 1533(b)(2).  Areas designated as occupied critical habitat must be specific areas within the area occupied by the species at the time the species is listed on which are found physical or biological features essential to conservation of the species; and which may require special management considerations or protection.  Id. § 1532(5)(A).  Designation of unoccupied critical habitat requires a separate determination by the Secretary that designation of such an area is “essential to conservation of the species.”  Id.

In Weyerhaeuser Co., plaintiffs challenged the designation of unoccupied critical habitat for the dusky gopher frog on the basis that land designated as unoccupied critical habitat was not habitable by the frog absent major changes to the land that the landowner did not plan to undertake and, therefore, should not be deemed critical habitat because the land did not constitute habitat.  Focusing on the plain language of ESA section 4, the Supreme Court observed that “[e]ven if an area otherwise meets the statutory definition of unoccupied critical habitat because the Secretary finds the area essential for the conservation of the species, Section 4(a)(3)(A)(i) does not authorize the Secretary to designate the area as critical habitat unless it is also habitat for the species.”  Id. at 368 (emphasis added).  The Court held that “[o]nly the ‘habitat’ of the endangered species is eligible for designation as critical habitat.”  Id. 

In August 2019, the Services took an initial step to address Weyerhaeuser by revising their regulations to require the presence of physical or biological features essential to the conservation of the species within areas designated as unoccupied critical habitat.  See 84 Fed. Reg. 45,020 (Aug. 27, 2019).  The Services added a requirement that, at a minimum, an unoccupied area must have one or more “physical or biological features” essential to the conservation of the species in order to be considered for designation as critical habitat.  In issuing the August 2019 final rule, the Services stated that they would define “habitat” for purposes of critical habitat designation in a separate rulemaking.  See id. at 45,049.

The Services’ Proposal

The Services’ proposal includes the following proposed definition of “habitat”:

The physical places that individuals of a species depend upon to carry out one or more life processes. Habitat includes areas with existing attributes that have the capacity to support individuals of the species.

The Services also propose an alternative definition of “habitat”:

The physical places that individuals of a species use to carry out one or more life processes. Habitat includes areas where individuals of the species do not presently exist but have the capacity to support such individuals, only where the necessary attributes to support the species presently exist.

The preamble to the proposed rule clarifies that the definition of habitat is intended “to fully encompass both the occupied and unoccupied prongs of the definition of ‘critical habitat’ in the Act.”  The Services invited comments on the proposal and related issues.  In response, stakeholders submitted over 160,000 comments.  The Services are now expected to consider comments received and then prepare a final rule to define “habitat.”


A final rule defining “habitat” will, as recognized by the Supreme Court in Weyerhaeuser, determine which areas are “eligible for designation as critical habitat.”  139 S. Ct. at 368.  The designation of critical habitat under the ESA can affect projects that require federal agency permits or funding, resulting in additional permit costs (such as additional environmental surveys and analyses) and longer planning horizons.  A clear definition of “habitat” would help clarify which areas may be considered by the Services for designation as critical habitat.  This clarification can be beneficial for species by aiding the public’s understanding of those areas that constitute habitat, and can be beneficial for regulated entities who are planning or undertaking projects in or near areas that constitute habitat.  For example, if a landowner plans to undertake voluntary conservation initiatives (i.e., habitat restoration, enhancement, or creation) that benefit the species and its habitat, understanding which features and areas constitute habitat could help inform those efforts and potentially avoid the need for listing the species or designating the area as critical habitat.  A clear definition of habitat could also help companies design their projects to avoid or limit impacts on habitat.  A clear definition should also aid members of the public in tailoring comments on proposed critical habitat designations to those areas and features that meet the definition of habitat.  In these and other instances, a clear definition of habitat should help stakeholders understand what features the Services will deem to be habitat for a species when considering the potential designation of critical habitat for that species.


  • Partner

    Andrew has significant experience in the natural resources space, focusing on wetlands, endangered species and the marine environment. He has been influential in shaping jurisprudence at the intersection of environmental ...


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