Global warming and biodiversity: Evidence of climate-linked amphibian declines in Italy

Amphibians are among the most endangered animals on Earth, and climatic shifts are among the hypothesized factors in their decline. We used spatial patterns of recent amphibian declines in Italy to test hypotheses pertaining to three potential, nonexclusive factors: climate change, habitat alteration, and high levels of incident solar radiation. This study was based on patterns of presence in a geographic grid for 19 species. Grid-squares in which presence had previously been documented, but was not re-confirmed after a specific threshold year, were considered to represent declines. Using a GIS-based approach, we calculated, for each cell, the mean values - or shift in mean values - of different parameters, used as proxies for the three factors. The measures of these parameters were entered as predictors in specific autocovariate models fitted on grid-square status. Our results suggest that while multiple factors have contributed to declines, climate change has been a major cause of population disappearances. We identified a common pattern of disappearances in areas that have been especially affected by climatic shifts. Our findings also strongly suggest that habitat alteration, due mainly to urban land use, has contributed to the decline of several species and that solar irradiation, though probably not a direct cause of mortality, may have been important in association with other stressors. By identifying the most threatened species, geographical hot spots of decline, and the primary causes of decline, our work provides a basis for improving management and setting conservation priorities.