As a result, the species protected under the Act today include not only the bald eagle and grizzly bear, but also mice, rats, snails, clams, beetles, spiders, and a fly, not to mention over 20 different kinds of cactus. Species are listed through a rulemaking process that provides for public input at various points. The Act details the factors the Services must consider in determining whether a species is endangered, including loss of habitat and other threats to the species. The Services may not consider the economic or social impacts of the listing decision. Critical habitat includes specific areas within and outside the geographic area occupied by the species at the time it is listed which contain physical and biological attributes essential to the conservation of the species and which may require special management considerations and protection.
Critical habitat can include private as well as government lands.
While the Act contemplates that the Services will designate critical habitat when a species is listed, this almost never happens in practice. The Services may decide that critical habitat is not currently determinable and extend the time for designation for up to a year. In addition, the Services may decide that designating critical habitat would not be prudent. Once species are listed, they automatically become subject to a variety of programs to protect and conserve them. The ESA contains a variety of prohibitions, including provisions restricting trade in endangered species.