On Wednesday, December 16, 2020, the U.S. Fish & Wildlife Service (the Service) finalized for the first time a regulatory definition for the term “habitat,” as the term is used in the Endangered Species Act (ESA) and the various implementing regulations. See 85 Fed. Reg. 81,411 (Dec. 16, 2020). The definition becomes effective on January 15, 2021. We previously reported on the Service’s publication of the proposed definition, 85 Fed. Reg. 47,333 (Aug. 5, 2020). A link to the prior post on the proposed rulemaking can be found HERE. Background A keystone element of the Service’s protection of threatened or endangered species under the ESA is the designation, conservation, and protection of “critical habitat.” Section 3(5)(A) of the ESA defines “critical habitat” to include: