50 C.F.R. § 424.12
Criteria for designating critical habitat
(a) To the maximum extent prudent and determinable, we will propose and finalize critical habitat designations concurrent with issuing proposed and final listing rules, respectively. If designation of critical habitat is not prudent or if critical habitat is not determinable, the Secretary will state the reasons for not designating critical habitat in the publication of proposed and final rules listing a species. The Secretary will make a final designation of critical habitat on the basis of the best scientific data available, after taking into consideration the probable economic, national security, and other relevant impacts of making such a designation in accordance with § 424.19.
(1) Designation of critical habitat may not be prudent in circumstances such as, but not limited to, the following:
(i) The species is threatened by taking or other human activity and identification of critical habitat can be expected to increase the degree of such threat to the species;
(ii) The present or threatened destruction, modification, or curtailment of a species' habitat or range is not a threat to the species;
(iii) Areas within the jurisdiction of the United States provide no more than negligible conservation value, if any, for a species occurring primarily outside the jurisdiction of the United States; or
(iv) No areas meet the definition of critical habitat.
(2) Designation of critical habitat is not determinable when one or both of the following situations exist:
(i) Data sufficient to perform required analyses are lacking; or
(ii) The biological needs of the species are not sufficiently well known to identify any area that meets the definition of “critical habitat.”
(b) Where designation of critical habitat is prudent and determinable, the Secretary will identify specific areas within the geographical area occupied by the species at the time of listing and any specific areas outside the geographical area occupied by the species to be considered for designation as critical habitat.
(1) The Secretary will identify, at a scale determined by the Secretary to be appropriate, specific areas within the geographical area occupied by the species for consideration as critical habitat. The Secretary will:
(i) Identify the geographical area occupied by the species at the time of listing.
(ii) Identify physical and biological features essential to the conservation of the species at an appropriate level of specificity using the best available scientific data. This analysis will vary between species and may include consideration of the appropriate quality, quantity, and spatial and temporal arrangements of such features in the context of the life history, status, and conservation needs of the species.
(iii) Determine the specific areas within the geographical area occupied by the species that contain the physical or biological features essential to the conservation of the species.
(iv) Determine which of these features may require special management considerations or protection.
(2) After identifying areas occupied by the species at the time of listing, the Secretary will identify, at a scale determined by the Secretary to be appropriate, specific areas outside the geographical area occupied by the species at the time of listing that the Secretary determines are essential for the conservation of the species. Such a determination must be based on the best scientific data available.
(c) Each critical habitat area will be shown on a map, with more-detailed information discussed in the preamble of the rulemaking documents published in the
(d) When several habitats, each satisfying the requirements for designation as critical habitat, are located in proximity to one another, the Secretary may designate an inclusive area as critical habitat.
(e) The Secretary may designate critical habitat for those species listed as threatened or endangered but for which no critical habitat has been previously designated. For species listed prior to November 10, 1978, the designation of critical habitat is at the discretion of the Secretary.
(f) The Secretary may revise existing designations of critical habitat according to procedures in this section as new data become available.
(g) The Secretary will not designate critical habitat within foreign countries or in other areas outside of the jurisdiction of the United States.
(h) The Secretary will not designate as critical habitat land or other geographic areas owned or controlled by the Department of Defense, or designated for its use, that are subject to a compliant or operational integrated natural resources management plan (INRMP) prepared under section 101 of the Sikes Act (16 U.S.C. 670a) if the Secretary determines in writing that such plan provides a conservation benefit to the species for which critical habitat is being designated. In determining whether such a benefit is provided, the Secretary will consider:
(1) The extent of the area and features present;
(2) The type and frequency of use of the area by the species;
(3) The relevant elements of the INRMP in terms of management objectives, activities covered, and best management practices, and the certainty that the relevant elements will be implemented; and
(4) The degree to which the relevant elements of the INRMP will protect the habitat from the types of effects that would be addressed through a destruction-or-adverse-modification analysis.