This extinction is unprecedented in both its breadth and speed. In the past 10,000 years, and especially the past 500, the rate of extinction of species has increased to somewhere between 100 and 1,000 times what it was before human history began. Scientists' conservative estimates suggest that a significant percentage of the world's species are likely to become extinct within the next several decades. Unlike all previous episodes of mass extinction, the one now under way is human-caused and can be stopped by timely action. The most common reason for the loss of biodiversity is loss of habitat.
Islands are especially vulnerable to species extinction.
Because of their isolation, many unique species have evolved on islands. When predators are introduced or habitat is destroyed, these species have nowhere to escape. The concentration of many endangered species in small areas also makes them especially vulnerable to climate change. Species on mountaintops or islands, for example, cannot easily migrate to new areas if global warming makes their environment too hot or too dry for them. In some areas, the ranges of endangered species are extremely small, and the dangers correspondingly great.