Polar bears were listed as a threatened species under the U.S. Endangered Species Act in 2008.
The word “threatened” can conjure alarming images of a species on the brink of disappearing forever. The term’s actual meaning, however, is not necessarily that dire—depending on who you ask.
There are two common systems of classifying a species’ extinction risk: The International Union for Conservation of Nature’s Red List of Threatened Species (IUCN) and the U.S. Endangered Species Act.
The Red List
Established in 1964, the Red List indicates the global conservation status of animals, plants and fungi. It keeps track of species that have undergone global assessments of their extinction risk and sorts them into eight categories: data deficient, least concern, near threatened, vulnerable, endangered, critically endangered, extinct in the wild and extinct. Under Red List guidelines, species that are rated vulnerable, endangered, or critically endangered are also considered threatened.
The status of a species on the Red List changes periodically. A plant or an animal that is considered threatened today may not be threatened a year from now. The Red List category that a species falls into depends on its population size, geographic range, past reductions in population, and probability of extinction in the wild.
Scientists count the number of each species in as many places around the world as possible and estimate the total population size with statistical methods. Then they determine the likelihood that it will go extinct in the wild by considering its history, habitat requirements, and threats.
Endangered Species Act
In 1973, the U.S. Congress passed the Endangered Species Act to try to prevent species from becoming extinct. The law classifies plants and animals as endangered if they’re at risk of extinction through all or most of their geographic areas. Species are listed as threatened if they’re likely to become endangered in the foreseeable future.
To classify a species, the U.S. Fish & Wildlife Service considers damage to its habitat, overuse of it, disease or predation, inadequate protection, and other factors. It’s illegal under the Endangered Species Act for a person to hunt, kill, capture, or otherwise harm a threatened animal without a permit. States might also have separate laws governing activity that involves endangered and threatened animals.
Unlike species listed as endangered, those classified as threatened under the Endangered Species Act can be taken from the wild for exhibition in a zoo or for educational reasons. State natural resource departments also can move threatened species if it’s part of a conservation effort. To protect a threatened species, the Fish & Wildlife Service can add other conservation-minded regulations.
The ultimate goal of the Endangered Species Act is to take species off the list of species that the act protects. When a plant or an animal is no longer marching toward extinction, the federal law has done its job.