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FROGS Amphibians have been hopping, swimming and crawling about the planet for 350 million years. But their future is hardly assured. A global assessment of the state of this entire class of vertebrates found that nearly one-third of the 5,743 known species are in serious trouble. Climate change may well be the culprit in most cases, either directly or indirectly. The home habitat of the golden toad (at right, bottom) in Costa Rica moved up the mountain until "home" disappeared entirely. More than two-thirds of the 110 species of colorful harlequin frogs in Central and South America, two shown above, have also disappeared. Scientists believe that what killed many of the harlequins and what threatens a great many other amphibian species is a disease caused by the fungus Batrachochytrium dendrobatidis. Climate change seems to be making frogs more vulnerable to infection by the fungus.
What troubles scientists especially is that if we are only in the early stages of warming, all these lost and endangered animals might be just the first of many to go. One study estimates that more than a million species worldwide could be driven to extinction by the year 2050.