As institutionalized in the U. S. Endangered Species Act of 1973, critical habitat is considered the area necessary to the survival of a species, and, in the case of endangered and threatened species, essential to their recovery. An animal's habitat includes not only the area where it lives, but also its breeding and feeding grounds, seasonal ranges, and migration routes. Critical habitat usually refers to the area that is essential for a minimal viable population to survive and reproduce. The Endangered Species Act is intended to conserve "the ecosystems upon which endangered species and threatened species depend." Thus, the Secretary of the Interior is required to identify and designate critical habitats for species that are listed as endangered or threatened under this law. In some cases, areas may be excluded from such designations if the economic, social, or other costs exceed the conservation benefits.

The listing of...