A Synthesis of Evidence of Drivers of Amphibian Decline

Abstract/Summary

ABSTRACT:—Early calls for robust long-term time series of amphibian population data are now being realized after 25 years of focused research. Inference from individual studies and locations have contributed to a basic consensus on drivers of these declines. Until recently there were no large-scale syntheses of long-term time series to test hypotheses about the generality of factors driving population dynamics at broad spatial scales. Through the U.S. Geological Survey Powell Center for Analysis and Synthesis, we brought together a group of scientists to elucidate mechanisms underlying amphibian declines in North America and Europe. We used time series of field data collected across dozens of study areas to make inferences with these combined data using hierarchical and spatial models. We bring together results from four syntheses of these data to summarize our state of knowledge of amphibian declines, identify commonalities among the results that suggest further avenues of study, and suggest a way forward in addressing amphibian declines – by looking beyond specific drivers to how to achieve stability in remaining populations. The common thread of these syntheses is that declines are real but not ubiquitous, and that multiple factors drive declines but the relative importance of each factor varies among species, populations and regions. We also found that climate is an important driver of amphibian population dynamics. However, the sensitivity to change varies among species in ways unlikely to explain overall rates of decline. Thirty years after the initial identification of a major catastrophe for global biodiversity, the scientific community has empirically demonstrated the reality of the problem, identified putative causes, provided evidence of their impacts, invested in broader scale actions, and attempted meta-analyses to search out global drivers. We suggest an approach that focuses on key demographic rates that may improve amphibian population trends at multiple sites across the landscape.

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