Science / Medicine : Frogs’ Decline Stirs Concerns

Populations of frogs, toads and salamanders appear to be declining mysteriously in many places around the world, and scientists fear the dramatic disappearance of the amphibians may be a sign of widespread environmental degradation of some unknown kind.

For several years, there have been rumors and scattered reports that frogs and toads appear to be far less common than they once were. More recently, many field biologists have begun documenting precipitous declines, sometimes measuring from 50% to 90%, and local extinctions in a variety of settings, from tropical forests to temperate mountain lakes.

“We are very concerned,” said David Wake of UC Berkeley. “There seems to be something going on, something we don’t yet understand.”

The cause of the decline remains a mystery. Some researchers suspect acid rain. But others believe the crashing populations could be caused by pesticides, viruses, hard winters or dry summers. In some locations, the frogs and other amphibians may have been wiped out by introduced competitors such as fish. The animals may also be exploited for food or even by scientists themselves, who collect specimens for research.