Global Change - Environmental Science - page 198

An endangered species is a population of organisms that is at risk of becoming extinct. Many species become
endangered due to habitat loss, changes in environment, hunting/poaching, introduction of a nonnative species,
disease, pollution, or a combination of factors. Many countries have established their own criteria for labeling
a species "endangered." In the United States, these criteria are put forth in the Endangered Species Act, which
describes two categories of danger:
• Endangered: Plants and animals that are so rare that they are in danger of becoming extinct.
• Threatened: Plants and animals that are projected to become endangered within the foreseeable future.
The International Union for Conservation of Nature (IUCN) was established to promote natural resource con-
servation. The IUCN has developed its Red List, which has three broad categories and smaller breakdowns
within those categories. The categories are:
• Extinct
• Extinct: The last remaining member of the species has died or is presumed to have died.
• Extinct in the wild: Only captive individuals of the population remain; no individuals of the species
are known to live in the wild.
• Threatened
• Critically endangered: The species faces an extreme risk of becoming extinct.
• Endangered: The species faces a high risk of extinction in the near future.
• Vulnerable: The species faces a high risk of extinction in the medium term.
• At Low Risk
• Near threatened: The species may be considered threatened in the near future.
• Least concern: There is no immediate threat to the survival of the species.
Three hundred known plant and animal species have gone extinct in North America since European coloniza-
tion. Approximately 750 North American plants and 1,200 animals are listed as endangered, with another
3,000 species proposed for listing. Only a few species have been removed from the list. As of May 2007, the
populations of endangered species have increased from historic lows and several species that were once en-
dangered have been removed from the list, while others have been moved from endangered to threatened. Five
species had recovered and been removed from the list entirely, including bald eagles, peregrine falcons, Amer-
ican alligators, gray whales, and grizzly bears. However, as of 2007, seven species had also been removed from
the list after becoming extinct, including Florida's dusky seaside sparrow, the Santa Barbara song sparrow, the
Tecopa pupfish, the Sampson's pearly mussel, the blue pike, the longjaw cisco, and the Amistad gambusia.
Losses Due to Habitat Destruction
According to researchers, the greatest threat to species is the loss, degradation, and fragmentation of habitats.
Perhaps the greatest loss is the deforestation of the tropical areas. Large areas of forest have been cut down for
their timber, or to plant grasses and corn for cattle production. Additionally, the destruction and degradation of
coral reefs resulting especially from harvesting for home aquariums and coral bleaching has created devastat-
ing habitat loss. The draining and filling of the world's coastal wetlands including mangrove swamps and salt-
water marshes has resulted in an over 50 percent loss of these habitats. Many countries' inland wetlands have
experienced a loss of more than 80 percent.
Large areas of grasslands have been plowed to grow food for animal and human consumption, to house large
farms to raise cattle and other farm animals, and, most recently, for the development of large cities. These