Extinction is forever, and it is far from an isolated process. Extinction means a branch of the evolutionary tree has died, and a distinct creature has passed from existence.
The loss of just one species can cause an entire ecosystem to falter or collapse. So, according to many biologists, the best way to preserve an individual species is to ensure the survival of all of its native plant and animal neighbors. But making plans to protect whole ecosystems involves dealing with a slippery subject: biodiversity.
What is biodiversity? It encompasses the richness of species and the range of their genetic makeup, communities of organisms, ecosystems, and entire landscapes. The Earth's ability to supply the resources humans need is dependent upon a naturally evolving combination of genes, species, populations, and ecosystems.
Since becoming law in 1973, the Endangered Species Act (ESA) has been the most powerful tool for protecting biodiversity in the United States. The Act attempts to prevent extinction by recognizing a species as either endangered╤at risk of becoming extinct in all or much of its range╤or threatened╤close to being endangered╤and providing strict protection for the species and its habitat. About 760 plant and animal species in the U.S. are listed as endangered or threatened, and 532 foreign species╤all but three are animals╤have such protection. Another 900 require immediate attention to determine whether they, too, are on the brink. The Act requires that a recovery plan╤a prescription for how to bring a species back from endangerment╤be developed for every listed species.
So far, only six species have been removed from the endangered list: the Atlantic population of the brown pelican, the Rydberg milk vetch, the Palau dove, the Palau fantail, the Palau owl, and the gray whale. In the case of the whale, which migrates annually along the Pacific coast between its winter breeding and summer feeding areas, the population increased from 1,500 to 21,000 in the years since the ESA was enacted.
So the ESA can save species, but not without costs. In 1991, state and federal agencies spent $177 million to protect endangered species.
Adapted from The Information Please Environmental Almanac compiled by World Resources Institute, published by Houghton Mifflin.
