Climate change identified as greatest threat to tropical frogs

A new study by researchers from several U.S. institutions suggests that climate change may be the most destructive force against tropical frogs.

While changes in climate and land use are expected to reduce the livable area for tropical frogs, the researchers have found that declines in frogs' thermally suitable habitat area from climate change alone could be up to 4.5 times greater than declines attributable to land-cover change only, such as converting a forest to agriculture.

Unlike humans, frogs rely on external sources to regulate their body temperature, so habitats in which frogs are unable to keep their body temperature below their maximum temperature limit are unlikely to support frog populations. At the same time, these species will increasingly encounter temperatures hot enough to harm their behavior, reproduction and physiology

For the study, published in the recent issue of the journal Conservation Biology, Ph.D. student David Kurz of the University of California, Berkeley, traveled to Costa Rica in Central America and conducted frog surveys in three land-cover types: forest fragments, heart of palm plantations and pasture. After 400 surveys, Kurz and lead author Justin Nowakowski, a postdoctoral researcher at University of California, Davis, identified frog species restricted to forest as well as species that were able to survive in the agricultural areas.

Based on the field data and information on frog thermal tolerances, the two researchers and their colleagues from John Carroll University, Zoo Miami and Florida International University modeled the shifting thermal landscapes of frogs to determine how much suitable habitat area would remain 80 years into the future for frogs with different thermal tolerances under a variety of land-use and climate scenarios.

"Our field data and subsequent modeling show that frogs that are better able to withstand rising temperatures have a better chance of survival in a rapidly changing world," Kurz was quoted as saying in a UC Berkeley news release. However, the researchers found that frog species living exclusively in forests were most sensitive to the high temperatures that come from the combination of climate change and forest conversion. Endit