No Single Reason For Amphibian Decline

With a number of potential causes for the decline, there may be no single reason, said Mike Lannoo, a biology professor and coordinator of the U.S. Declining Amphibian Task Force.

"Certainly in every industrialized country, amphibian populations have been declining for some time," he said. "The question is if it is a slow or fast decline. It will take a great deal of research over time to determine that."

Declines are being blamed on various causes, including habitat destruction, chemical contamination, changes in the ozone layer, global warming, acid rain, parasites and viruses.

In many locations, some amphibian species are declining while other population groups seem to be stable. There also have been increased incidences of malformed frogs, including those with extra sets of eyes or legs, he said.

"I study an area in northwest Iowa and we've seen 30 deformed frogs over 20 years and that is probably because at one site the spring fed water is colder than it should be for proper development," Lannoo said. "Yet, at spots in Minnesota we are seeing upwards of 70 percent of the frogs malformed."

Malformations may not necessarily be blamed for declining populations, pointing out that deformities were discovered in pre-industrialized America, he said.

Lannoo said more research is needed because amphibian populations have increased and decreased regularly in recent history, making it difficult to determine a long-term trend.

"There are probably natural and non-natural causes for the population declines and subsequent malformations we are seeing," he said. "We have to do more research and weed out the various factors."

Lannoo, who has researched amphibians for more than a decade, believes that the loss of any animal species is a sign the environment is in poor shape.

"It is not good news to have fewer amphibians just like it is to have fewer manatee, beluga whales and other animals," Lanno said. "Some people argue that the loss of amphibians is an indicator of poor ecological health because amphibians live both on land and water.

"While some people label amphibians as a warning signal to humanity, I don't go that far because there has been no clear demonstrated links between amphibian declines and human disease," he said.