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Global warming may be key factor in frog deaths

Global warming may be key factor in frog deaths

Global warming may be key factor in frog deaths
May 28, 2007

Three papers published in this week’s issue of the journal Nature debate the proximate causes for the global decline of amphibians, but nonetheless reveal mounting concerns among scientists over the continuing disappearance of frogs, salamanders, and their relatives.

Two papers criticize a 2006 paper led by ecologist Alan Pounds, which argued that the primary factor of amphibian decline is the deadly chytrid fungus Batrachochytrium dendrobatidis, the outbreak of which is worsening due to climate change.

In the first paper, Ross A. Alford, Kay S. Bradfield and Stephen J. Richards says that populations of two frog species in tropical Australia show “increasing developmental instability, which is evidence of stress at least two years before they showed chytrid-related declines.” They say the findings suggest that the Pounds et al. model is incomplete and “their test of the climate-linked epidemic hypothesis could be inconclusive.”

In the second paper, Ines Di Rosa, Francesca Simoncelli, Anna Fagotti and Rita Pascolini report that water frogs in Italy were already in decline before chytridiomycosis, as the fungal disease is known, was observed. “We show that the chytrid was common there throughout 1999—2002, in a previously unknown form that did not cause disease,” wrote the authors. “We therefore think that the focus by Pounds et al. on a single pathogen is hard to justify because the host—parasite ecology is at present so poorly understood.”

In a third paper, Pounds and colleagues respond to the criticisms, arguing that their working model was “appropriate” and highlighting the complexity of amphibian decline, which likely results “as global warming conspires with various other agents.” Pounds et al. note that the new research supports the contention that climate change is playing a role in the biodiversity crisis.

According to the Global Amphibian Assessment, a comprehensive status assessment of the world’s amphibian species, one-third of the world’s 5,918 known amphibian species are classified as threatened with extinction. Further, more than 170 species have likely gone extinct since 1980. Scientists say the worldwide decline of amphibians is one of the world’s most pressing environmental concerns; one that may portend greater threats to the ecological balance of the planet. Because amphibians have highly permeable skin and spend a portion of their life in water and on land, they are sensitive to environmental change and can act as the proverbial “canary in a coal mine,” indicating the relative health of an ecosystem. As they die, scientists are left wondering what plant or animal group is next.

Recent articles on the amphibian crisis

Scientists find possible cure for global amphibian-killing disease
(5/23/2007) Scientists have discovered a possible treatment for the fungal disease that has killed millions of amphibians worldwide. Presenting Wednesday at the General Meeting of the American Society for Microbiology in Toronto, Professor Reid N. Harris at James Madison University reported that Pedobacter cryoconitis, a bacteria found naturally on the skin of red-backed salamanders, wards off the deadly chytridiomycosis fungus, an infection cited as a contributing factor to the global decline in amphibians observed over the past three decades.

Frogs avoid damaging UV-B radiation, reducing extinction risk
(4/18/2007) Poison arrow frogs appear to make special effort to avoid exposure to damaging ultraviolet-B radiation, according to research published in the journal Biotropica. The findings are significant in light of increasing levels of UV-B radiation due to ozone depletion.

Bad news for frogs; amphibian decline worse than feared
(4/16/2007) Chilling new evidence suggests amphibians may be in worse shape than previously thought due to climate change. Further, the findings indicate that the 70 percent decline in amphibians over the past 35 years may have been exceeded by a sharp fall in reptile populations, even in otherwise pristine Costa Rican habitats. Ominously, the new research warns that protected areas strategies for biodiversity conservation will not be enough to stave off extinction. Frogs and their relatives are in big trouble.

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