A retrospective overview of amphibian declines in Brazil's Atlantic Forest

Amphibians are facing population declines and extinctions across the globe, and megadiverse Brazil is no exception. One of the global hotspots of amphibian declines is Brazil's Atlantic Forest (AF), an ecoregion that in the past covered over 1,300,000 km² of luxuriant coastal rainforests. Reports of historical declines were concentrated in the southern and southeastern sections of AF, however we now propose that these reports did not capture the whole extent and complexity of historical amphibian declines. Here, we conducted a refined review of historical amphibian declines that have been linked to environmental factors, climatic anomalies, and the emergence of the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd). We reviewed data on 169 populations of 106 species that have undergone population declines in the southern and southeastern Atlantic Forest, more than doubling the number of population declines reported in previous studies. These numbers place the Atlantic Forest among the ecoregions with the highest rates of amphibian declines and extinctions globally. We provide novel spatiotemporal information of amphibian declines, underscoring that the peak of declines happened in 1979, and that population recoveries, when they occurred, often took over 30 years. Our analyses indicate that the volume of field collections accessioned in museums over time matched temporal patterns of declines and extinctions, which indicates that historical declines might have impacted a far larger number of amphibian populations and species. Our review helps guide targeted management programs for amphibian surveys and Bd surveillance with practical implications for conservation.