THE EXTINCTION CRISIS
Ancient forests, free-flowing rivers, living oceans and deserts and the abundance of life they contain: All these, having evolved over millions of years, are in danger of vanishing from the world within decades. In the grip of a wave of extinction that is unprecedented in history, we are now seeing the disappearance of biological and habitat diversity across the globe as wild lands and waters are destroyed and species driven extinct.
Although extinction is a natural phenomenon, it is believed to occur at a natural “background” rate of about one to five species per year. Experts believe we are now losing dozens of species per day — anywhere from 100 to 10,000 times higher than the background rate. Current extinctions are generally brought about by people, and 99 percent of currently threatened species are at risk from human activities, including those driving global warming.
The World Conservation Union, or IUCN, has documented the extinction of 849 species in the wild since 1500 A.D. (when historical scientific records began), but this does not account for thousands of species that disappear before scientists can even describe them. As of 2006, more than 16,000 species worldwide were threatened with extinction, but this is likely a gross underestimate because fewer than 3 percent of the world’s 1.9 million described species have been assessed by IUCN’s Red List.
One out of every eight bird species assessed by IUCN is threatened with extinction. Habitat loss and degradation have caused most of the bird declines, but the impacts of invasive species and capture by collectors play a role as well. At least 270 South American birds are IUCN-listed as endangered, and there are more than 60 endangered or threatened owl species around the world.
Because of human impacts, amphibian species are in severe decline. A 2004 Global Amphibian Assessment by IUCN concluded that an alarming one-third (1,856 of 5,743) of the planet’s known amphibian species are threatened with extinction. Frogs, toads and salamanders are disappearing because of habitat loss, water and air pollution, climate change, ultraviolet light exposure, introduced exotic species, and disease. Vanishing amphibians should be viewed as the canary in the global coal mine, signaling subtle yet radical ecosystem changes which could ultimately claim many other species including humans.
Globally, 1,094 species of mammals, or about 20 percent of the total 5,416 described mammal species, were deemed endangered or vulnerable to extinction by IUCN's 2007 Red List. Forty-one of 457 species risk extinction in the United States, or about 9 percent of the total. Among those mammals that are most critically endangered are primates, which are on the extinction frontlines. About 90 percent of primates — the group that contains monkeys, lemurs, lorids, galagos, tarsiers, and apes (as well as humans) — live in tropical forests, which are fast disappearing.
Large-scale commercial fishing, shipping, and oil drilling have pushed many marine species to the brink of extinction and beyond, and the oceans' animals and natural systems are now in serious decline. Oceans and the extraordinary life they contain are under severe pressure from pollution, massive overfishing, and runaway development along fragile coastline ecosystems. Commercial fisheries are collapsing around the globe as species in, above, and around the oceans are being killed off at breakneck pace. Twenty marine mammals are already listed as endangered or threatened under the U.S. Endangered Species Act.