观看免费视频 Decline in Amphibian Populations

Amphibians have been one of Earth's great survivors -- evolving about 400 million years ago before the dinosaurs, persisting through ice ages, asteroid impacts, and myriad other ecological and climatic changes.
But today amphibian declines and extinctions have no precedent in any animal class over the last few millennia.
About 32% of some 6000 amphibian species are threatened as compared to12% of bird and 23% of mammal species. Up to 122 amphibian species may be extinct since 1980, and population size is declining in at least 43% of species. In the last decades of the 20th century the amphibian extinction rate exceeded the mean extinction rate of the last 350 million years by at least 200 times.
The amphibian declines are linked to natural forces such as competition, predation, reproduction and disease, as well as human-induced stresses such as habitat destruction, environmental contamination, invasive species
and climate change.