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Spring 2004 Table of Contents.
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Twenty years ago, the world's scientists sounded an alarm on behalf of frogs, toads and salamanders.

Researchers with years of experience began noticing sharp declines in amphibian populations. Early evidence was based on field observations and was often anecdotal, but the conclusion seemed incontrovertible: many amphibian species were on the brink of extinction, and no one could say why.

In years since, amphibian research has grown more technologically sophisticated and better funded. Most importantly, it has come to be defined within the larger issues of habitat and biodiversity conservation, says Ray Semlitsch, a professor of biology at MU who has been in the thick of amphibian research -- and at the forefront of its change -- since 1975.

Today Semlitsch is one of only a handful of researchers dedicated solely to applied amphibian conservation issues. "The issue that arose was whether amphibians were somehow declining more rapidly or being affected differently than other taxa, such as fish, birds or mammals. Most people agree today that amphibians are just part of the biodiversity crisis. They are not suffering any more or any less than other taxa."

Most amphibians are soft-skinned, semi-aquatic, seemingly delicate creatures with a physiology that falls somewhere between fish and reptiles. Because they are so intimately tied to both land and water, amphibians are among the most vulnerable of all animals to human
disturbance. And while as a group they may be in no worse shape than other types of wildlife, scientists often point to them as proverbial "canaries in a coal mine" when it comes to measuring the health of vital wetlands.

In short, they argue, what's good for amphibians is good for dozens of other species. "We are trying to establish reasons why small wetlands are important for more than just amphibians. Reptiles, migratory birds, insects and small mammals all need them," Semlitsch says.

Researchers must look beyond the study of individual species and local populations, he adds, and look toward understanding larger ecological processes that contribute to species survival in the face of human encroachment. Only then will they learn how to devise conservation strategies to preserve their habitats and perhaps stave off further extinctions.

Before the population crisis of the 1980s, amphibian researchers tended to focus on basic biological functions and life histories of individual species. By the early 1990s, that had changed. These days, scientists tend to work by logging long-term data sets about populations and ranges, then completing meta-analyses of that data. Such analyses in Europe and North America, for example, have shown that more than 200 amphibian species have experienced declines, and that 32 species have become extinct.

"We know they are declining, we know they're in trouble," says Semlitsch. "We've identified the threats, and identified many of the major interactions among the threats." The list of these threats makes for sobering reading: global climate change, chemical contaminants in terrestrial and aquatic environments, diseases and pathogens, exploitation by collectors for commercial markets, and competition from exotic or invasive species.

And this list doesn't even include what is perhaps the chief factor contributing to amphibians' demise, a threat familiar to anyone who's spent an afternoon watching Animal Planet: the loss of essential habitats. Frogs, toads and their kin have in recent years faced stepped-up competition for survival against humankind's insatiable hunger for agricultural land, forest products, industrial growth and the sprawl that accompanies suburban living. In short, we humans are destroying and sharply fragmenting all forms of natural habitats that the world's more than 5,500 species of amphibians need for survival.

       
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