On December 28, 1973 President Richard Nixon signed the Endangered Species Act of 1973, designed to protect critically imperiled species from extinction as a consequence of economic growth and development untempered by adequate concern for conservation and the environment.
"The stated purpose of the Endangered Species Act is to protect species and also "the ecosystems upon which they depend." It encompasses plants and invertebrates as well as vertebrates. It does not expressly include fungi, which were widely considered to be plants in 1973, [but which are now considered more closely related to animals than plants.]
"ESA is administered by two federal agencies, the United States Fish and Wildlife Service (FWS) and the National Oceanic and Atmospheric Administration (NOAA) (which includes the National Marine Fisheries Service, or NMFS). NOAA handles marine species, and the FWS has responsibility over freshwater fish and all other species. Species that occur in both habitats (e.g. sea turtles and Atlantic sturgeon) are jointly managed."
"Few species have become extinct while listed under the Endangered Species Act, and 93% in the northeastern US have had their population sizes increase or remain stable since being listed as threatened or endangered. As of August, 28, 2008, there are 1,327 species on the threatened and endangered lists. However, many species have become extinct while on the candidate list or otherwise under consideration for listing" (Wikipedia article on Endangered Species Act, accessed 06-13-2009).