In a policy statement to be published Friday in the journal Science, the scientists say that 32 percent of all amphibian species are threatened and at least nine – perhaps as high as 122 – have become extinct since 1980. It's time, they say, for a more organized and effective approach to address the various diseases, habitat loss, invading species and other causes of this problem.
"This is part of an overall biodiversity crisis, and amphibians seem to have been hit the hardest of all vertebrate species," said Andrew Blaustein, a professor of zoology at Oregon State University and one of the pioneers in this field, who first helped document amphibian declines almost 20 years ago.
"These are bioindicators that something is wrong with the planet," he said. "But amphibians play a major role in many ecosystems, in some places the amphibian biomass is greater than that of all the other vertebrates. The long term ecological repercussions of their decline could be profound, and we have to do something about it."
Programs of research, training, monitoring, salvage operations, disease management, captive breeding, and other efforts are envisioned under the new initiative, which may include a global network of centers for amphibian recovery and protection. Support from individuals, government agencies, foundations, and the conservation community will be sought, the researchers said in their report.
Amphibians have been around for more than 300 million years, thriving before the dinosaurs and living long after they and many other species had disappeared. Their dramatic decline and extinctions now has alarmed many researchers since it first became apparent in the past two decades.
"Amphibians have sensitive skin, they live in both land and water, have no protective hair or feathers, and their eggs have no hard outer shell," Blaustein said. "So it's clear why they may be vulnerable on some levels. However, they persisted for hundreds of millions of years and just now are disappearing in many areas."
Some of the causes have been identified. Rising levels of ultraviolet radiation, increases in pollutants, pesticides, extensive habitat loss due to agriculture or urbanization, invasive species, and various fungal diseases have all been implicated.
In viewing this issue, some biologists have called amphibians the "canary in the coal mine" - the first clear and sweeping biological example of environmental change, pollution and toxicity that may ultimately affect many other animal species, including humans. The demise of amphibians also has ecological ripple effects – they provide a major control of insect pests, and in turn serve as part of the food supply for birds, fish and other animals. The demise of entire species also eliminates their possible use in biomedicine and biotechnology.
One of the leading problems is a fungus that causes an infectious disease called chytridiomycosis, the researchers said in their Science report. In places where it is introduced and has not previously been present, amphibian populations may disappear rapidly, sometimes within six months, the researchers said. Global climate change, the commercial trade of wildlife, and pollution may all increase the movement or susceptibility to this fungus.
"There are a lot of concerns, and we should work to address all of them, not just one," Blaustein said. "At first we need to focus our efforts on research so we have a better idea of what types of recovery programs will best work, and then we need active projects in the field."
Scientists at OSU and the University of California/Berkeley were among the first in the world to sound the alarm bell about amphibian decline, publishing some professional papers in the early 1990s that alerted the world to the magnitude of this problem. One publication by this group has been listed as the 10th most cited paper ever in the journal Conservation Biology. OSU researchers also were among the first to link amphibian declines directly to global climate change, in a process that traced global warming ultimately to a catastrophic egg mortality in the western toad of the Pacific Northwest Cascade Range.
Work is continuing at OSU today on contaminants and the effects of UVB solar radiation that may amplify the impacts of the fungus which causes chytridiomycosis.
Amphibian declines have been documented in North and South America, Europe, Asia and Africa. Several species in the Pacific Northwest are listed as candidates for the endangered species list. More than a dozen species have disappeared from Australia in recent years. And the problem appears to be getting worse.
Traditional programs and current laws and policies alone are insufficient to address global threats that cross boundaries of reserves and nations, the scientists said in their report.
Andrew Blaustein | EurekAlert!
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