It's a Frog's Life Frogs are amazingly diverse. You can find them in tropical rain forests, north of the Arctic Circle, high in the Himalaya Mountains and in many of the world's driest deserts. They've also been around a lot longer than you might think. Frogs first appeared at least 190 million years ago, when Earth was still dominated by dinosaurs. Their ancestors were the first large animals to live on dry land. Today, there are close to 5,000 known frog species, and the list continues to grow as scientists probe deeper into the remote corners of the planet. Together with salamanders and caecilians (worm-like creatures that live mainly underground), they are amphibians -- animals that live part of their lives in water and part on land. But frogs are in trouble.

Fewer than 30 years ago, herpetologists -- scientists who study amphibians and reptiles -- began to notice that frogs were disappearing from areas where they once thrived. By 1989, amphibians were in dramatic decline all over the world, and it wasn't just in areas crowded with people. Many species were disappearing from the remote wilderness as well. "Until that point, I don't think anybody realized that it was anything other than a local problem," says one veteran biologist. Different species face different threats. The destruction of their habitat, overharvesting by humans, competition from other species and deadly diseases cause local problems. Pollution, climate change and increased radiation from the sun may be making matters worse on a global scale. Some 32 frog species are now thought to have died out since the early 1970s, and another 25 are classified as "missing in action" -- they're either extinct, or so rare that scientists haven't been able to find them.

Almost a hundred others are critically endangered. While these lists are likely to grow, there is hope. During the past decade, researchers have been working together and sharing information on frog declines. They're learning more about what's killing the frogs -- and what needs to be done to save them.