January 16, 1996
Web posted at: 10:30 a.m. EST
From Correspondent Don Knapp
SANTA CRUZ, California (CNN) -- Frogs are proving to be good indicators of problems in the environment.
Scientists studying the reduction of populations of frogs and other amphibians have unearthed new clues that point not only to the usual environmental suspects, such as habitat destruction, but also to pollution and loss of ozone layer protection.
The clues also can reveal that some environmental problems, like acid rain and intense solar rays, can combine to have a surprisingly deadly effect.
The combination is worrisome not only for amphibians but for people as well. "We think the most important thing about this study is the combination, the double-barreled effect of both acid rain and the ultraviolet light. The combination is much more harmful than either one by itself," said Michael Soule of the University of California in Santa Cruz.
In the late 1980s, Oregon State University researchers began to suspect that increasing levels of ultraviolet radiation killed certain frog eggs in clear mountain ponds while the same frogs thrived in protected laboratory tanks.
Scientists theorized that a thinning ozone layer allows the harmful rays to reach the Earth. Researchers also learned that the eggs of some frogs and other amphibians have a protective enzyme that repairs ultraviolet damage. Those survived better than eggs without the enzyme.
But ultraviolet radiation alone does not explain all of the losses to the world's amphibian populations. "To make things simple, scientists study one thing at a time," Soule said. "That's a better way to control the experiment. But we felt in nature, factors often work in combination."
Soule and graduate students at the University of California in Santa Cruz looked at the whole picture of air pollution, water pollution, exotic predators, development, and damage to the ozone layer and found a message that something was definitely wrong.
"Amphibians have terrestrial and aquatic stages," said biologist Michael Schmieder. "They're pretty close to the environment so one might expect, if there's a problem in the environment, amphibians are going to be first to go and they could be an indication of a bigger problem."
In addition to frogs, the scientists looked at California newts, which also lay their eggs in water and could be susceptible to the same light problems.
Researchers say that frogs and newts in ponds can function like canaries in coal mines, warning people of the dangers of a damaged environment.
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