Endangered Species
Some species adapt to natural changes in their environment such as climate change and increased competition from other species. The two to four million plants and animals that exist today have adjusted to meet these challenges, out of the estimated 500 million species that have existed since life began on Earth. Because of increased human activities around the world that destroy other habitats, most extinction (death of a species in the wild) has occurred over the past 200 years. With the accelerated destruction and pollution of the world's tropical rain forests, in particular, at least 500,000 insect, plant, and animal species are expected to disappear over the last two decades of the twentieth century.
Before a species becomes extinct, it is classified by the International Union for the Conservation of Nature and Natural Resources (IUCN) as either endangered, critically endangered, threatened, or rare. An endangered species faces immediate danger of extinction even with human action, while a critically endangered species is one that will not survive without human intervention and protection. Threatened species may still be abundant in their own habitat but their population is rapidly declining; a rare species is considered at risk because of low overall population numbers.
Most species become threatened and endangered because of a combination of factors: their habitat is either disturbed or eliminated (most often as a result of human activities); commercial and sport hunting are not managed to prevent population declines; competing species overtake the primary food sources; or the species is killed to protect livestock and crops. More than two-thirds of the species listed as endangered by the IUCN and the United States, through its Endangered Species Act, are included because their habitats were overtaken by human activities, and particularly land development. Large animals and birds such as the lion, Bengal tiger, elephant, and California condor are at increased risk because they require large areas of habitat for survival and breed in low numbers. Thus, the chances that they can adjust to human encroachment of their native habitat are low.
Various international and national laws have been passed to try to reverse the extinction of hundreds of plants and animals. In the United States, the primary law governing species protection and rehabilitation is the Endangered Species Act, first passed as the Endangered Species Conservation Act in 1966 and revised to its present name in 1973. The act commits the federal government, in cooperation with state and local governments, to develop recovery plans and other methods to protect and restore endangered and threatened plants and animals. Individuals and groups can sue to halt an action that is considered to violate the act, and federal agencies must not initiate projects that would jeopardize endangered species or modify habitats critical to their survival. This last requirement has been frequently debated in subsequent revisions of the act, and in 1998, the U.S. Congress is again revisiting the act's provisions.
One of the first species placed on the nation's endangered list was its national symbol, the bald eagle. In May 1998, the bird was delisted, as was the gray wolf, American peregrine falcon, tidewater goby fish, and almost one dozen other species. Since the act was passed, less than 1% of listed species have become extinct. As of mid-1998, 1,135 species, including 466 animals and 669 plants, are included on the endangered species list.
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