No global warming link to dying frogs?
March 25, 2008
Writing in the March 25 issue of PLoS Biology, a team of researchers led by Karen Lips of Southern Illinois University-Carbondale report finding "no evidence to support the hypothesis that climate change has been driving outbreaks of amphibian chytridiomycosis" — a disease blamed for large-scale die-offs of amphibians. Other researchers have argued that climate shifts are worsening the outbreak of the fungal disease.
Instead Lips and colleagues say that multiple introductions of the invasive pathogen are responsible for outbreaks in South America. Their work is based on modeling of the geographic decline of colorful harlequin frogs (genus Atelopus) in Central and South America and showed that fungus-linked declines are spreading in a wave-like pattern typical of highly virulent epidemics and unaffected by climate variables.
Other studies have found a similar pattern of decline in Eastern Australia.
Implications for conservation
Lips says the new study provides clues that could help limit the spread of the killer fungus.
"What makes the study really relevant is we can now generalize how the fungus is spread," Lips said. "We know from our research, that if we start looking in the right time and place in an area where the fungus is, we're probably going to see it affecting frog populations. This helps us understand what's going on, and it can potentially help us get out in front of it."
Lips says that since the fungus can be spread via the ornamental plant and aquarium wildlife trade, governments and environmental agencies should test on imports for the presence of the pathogen. Once discovered, anti-fungal drugs can destroy the fungus before it can contaminate an area.
"At this time, the fungus cannot be controlled or managed in wild amphibians nor their habitats," added co-author Michael W. Sears, also a zoologist at Southern Illinois University Carbondale.
The bigger picture
There are 6,000 known species of amphibians -- cold-blooded animals that include frogs, toads, salamanders, newts and caecilians -- worldwide.
Globally, 43 percent of amphibian populations are in decline according to the Global Amphibian Assessment. Other studies have cited habitat loss, pollution, pesticide-use, increased UV-B radiation, and the introduction of alien invasive species as possible factors in the decline.
In recognition of their plight, the "Amphibian Ark" — a coalition of zoos, botanical gardens and aquariums — has designated 2008 as "The Year of the Frog". Amphibian Ark is seeking to raise $50-60 million as part of a 5-year $400 million Amphibian Conservation Action Plan to establish captive breeding programs for the 500 most threatened species.
Lips, K.R. et al (2008). Riding the Wave: Reconciling the Roles of Disease and Climate Change in Amphibian Declines. PLoS Biology Vol. 6, No. 3, e72 doi:10.1371/journal.pbio.0060072
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