An endangered species is a species that is in immediate danger of becoming extinct. The designation of endangered to a species means that there is still time to save it but once it is extinct it is gone forever. Also of concern are threatened species, species whose numbers are low or declining but not in immediate danger of extinction. A threatened species is likely to become endangered if it is not protected.

Most species that are endangered are found in only limited geographic areas. Because these plants or animals are not widespread to begin with, they are more likely to be affected by major or catastrophic changes in their environment. Widespread common species, while sometimes significantly hurt by a regional catastrophe, are more likely to survive because many individuals will escape the damage elsewhere. In contrast, species found only in small and unusual habitats can suddenly...