Looming extinction crisis

The American black bear is one of more than 22,000 species threatened with extinction. During the past century, animals have been disappearing about 100 times faster than they used to, scientists from different American universities warned in a new study. According to the WWF, around 70 species go extinct every day.

According to the International Union for Conservation of Nature - which publishes a "red list" of threatened and endangered species - 41 percent of amphibian species and 26 percent of mammals are facing extinction. This Titicaca water frog, found only in Lake Titicaca in South America, used to be present in the millions in the early 1970s. By now, they have disappeared almost completely.

The causes of species loss are mostly manmade. They range from climate change, to pollution, to deforestation and beyond. About 2,000 trees have been cut down every minute during the past 40 years, according to a different study.

The world is embarking on its sixth mass extinction event, the current study concludes. The modern rate of species loss was compared to "natural rates of species disappearance before human activity dominated." The dodo (pictured above) was pushed to extinction by the introduction of nonnative species in 1690 - only 100 years after it had been discovered on Mauritius.

The study is based on documented extinctions of vertebrates - or animals with internal skeletons - from fossil records and other historical data. These results are estimations, since humans don't know exactly what happened throughout the course of Earth's history. In earlier extinction events, such as the Ice Age, only two out of 10,000 mammals died out per century - such as this primordial horse.

As species disappear, so do crucial services, such as pollination of crops by honeybees. At the current rate of species loss, humans will lose innumerable biodiversity benefits within three generations, the study's authors write. "We are sawing off the limb that we are sitting on," wrote author Paul Ehrlich from Stanford University.

If the current rate of extinction is allowed to continue, "life would take many millions of years to recover and our species itself would likely disappear early on," wrote lead author Gerardo Ceballos of the Universidad Autonoma de Mexico.

The study calls for "rapid, greatly intensified efforts to conserve already threatened species, and to alleviate pressures on their populations - notably habitat loss, over-exploitation for economic gain and climate change." In the meantime, the researchers hope their work will contribute to conservation, the maintenance of ecosystem services and biodiversity-oriented public policy.