The Global Amphibian Decline:
Trends, Causes, and Challenges

Red-eyed leaf frog
(Agalychnis callidryas)
photo by Jeff Chow

Global Trends
North America
Central and South America
Australia
Europe

Causes
Habitat Modification
Exotic Species
Acidification and Toxic Contiminants
Ultraviolet Radiation
Climate Change
Pathogens

Challenges

Bibliography

Links

Potential Cause: Climate Change

Alterations in local weather conditions caused by global climate change can influence the ecology of amphibians by forcing populations to shift habitat use and spawning times. These alterations include changes in precipitation patterns and temperatures, as well as the short-term damage on habitats caused by unusually violent storms. Because moisture is a critical resource for amphibian reproduction, reduction or changes in rainfall patterns could reduce amphibian reproduction and recruitment.

Climate change is implicated in the demise of the golden toad (Bufo periglenes) and harlequin frog (Atelopus varius) in Costa Rica's Monteverde Cloud Forest Preserve. Abnormally dry and hot weather, coupled with the particularly severe 1986-1987 El Nino/Southern Oscillation, led to demographic changes among a suite of vertebrate species, including amphibians. The warm, dry conditions that occurred at the onset of the breeding season likely caused breeding pools to dry, resulting in the deaths of virtually all eggs and tadpoles. Some species populations, such as the red-eyed leaf frog (Agalychnis callidryas, above) reappeared with the onset of wet-season rains, only to disappear afterwards. Following the crash, wet-season abundances of four remaining aquatic-breeding species experienced downturns that corresponded to subsequent dry years, lending support to the proposal that severe climate was the factor responsible for the declines in Monteverde.

Amphibian extirpation at Monteverde also could have occurred as a result of the combined effects of reduced precipitation, desiccating temperature conditions and other factors. Water loss or temperature stress could have weakened immune systems, resulting in greater vulnerability to pathogens. Also, warm, dry conditions could have led to habitat patchiness and highly clumped population dispersion patterns that facilitate diseases transmission. Also, long-range contamination of pesticides in Costa Rica, combined with the unusually severe dry season, could have caused the deleterious accumulation of contaminants typically present only at sublethal background levels.