From NOAA:
This year we celebrate the 40th Anniversary of the Endangered Species Act (ESA). President Nixon signed the ESA into law on December 28, 1973. Congress understood that, without protection from human actions, many of our nation’s living resources would become extinct.
Endangered species—in danger of extinction throughout all or a significant portion of its range.
Threatened species—likely to become an endangered species within the foreseeable future.
There are approximately 2,100 total species listed under the ESA. Of these species, approximately 1,480 are found in part or entirely in the U.S. and its waters; the remainder are foreign species.
Species diversity and environment health are part of the natural legacy we leave for future generations. Each plant, animal, and their physical environment are part of a much more complex web of life, where the removal of a single species could cause a series of negative events affecting many others. Endangered species serve as a sentinel, indicating larger ecological problems that could alter ecosystem functions. The ESA is both a mechanism to help guide our conservation efforts and a reminder that future generations deserve the opportunity to enjoy the same great benefits from the natural world.
We Will Continue the Work We Started
Today the ocean is a very different place than it was 40 years ago. Thanks to the ESA, we now understand many of the threats faced by marine and anadromous species and are bringing them under control. The populations of many listed species are increasing, aided by our recovery efforts and time. Still, the populations of many species continue to decline and many more species are being listed. NOAA Fisheries scientists are developing the next generation of ocean observing systems, which will give us Increased awareness of what’s going on in the ocean, adapt our management, and respond to challenges of a changing climate. We will continue developing new technologies and management approaches, and our work with national and international partners, to ensure the ESA remains effective in an interdependent, rapidly-changing world.
More endangered/threatened species coverage here.