Extinction and Endangered Species - What Are Endangered Species?

A species is described as extinct when no living members remain. Scientists know from the study of fossils that dinosaurs, mammoths, saber-toothed cats, and countless other animal and plant species that once lived on Earth no longer exist. These species have "died out", or become extinct. Once a species is extinct, there is no way to bring it back.

The U.S. government defines endangered species as those that are at risk of extinction through all or a significant portion of their natural habitats. Threatened species are defined as those likely to become endangered in the foreseeable future. The management at the federal level of endangered and threatened species is handled by two agencies, the U.S. Fish and Wildlife Service (FWS) and the National Marine Fisheries Service (NMFS). The FWS is an agency of the Department of the Interior and oversees the terrestrial (land-based) and freshwater species. The NMFS is an agency of the National Oceanic and Atmospheric Administration (NOAA) under the U.S. Department of Commerce. The NMFS is responsible for marine (ocean-dwelling) species and those that are anadromous (migrate between the ocean and freshwater).

The U.S. Fish and Wildlife Service maintains a list of species that are endangered or threatened in the United States and abroad. Both endangered and threatened species are protected by laws intended to save them from extinction. In many cases, recovery plans for endangered species have also been developed and implemented. These include measures designed to protect endangered and threatened species and to help their populations grow.