Wish you were here: How defaunated is the Atlantic Forest biome of its medium- to large-bodied mammal fauna?

Mammalsrepresent the largest-bodied elements of the world’s surviving megafaunaand provide several key ecosystems services, yet their populations are often under steep decline throughout the tropics. Anthropogenic defaunationis one the most important contemporary threats to modern mammalfaunas. Although the Atlantic Forest biomeof South America shows several clear signs of defaunation, the extent to which this biomehas lost its mammalfauna remains poorly understood. Here, we collate and analyze a comprehensive body of secondary data to quantitatively assess the spatial patterns of defaunationof all medium- to large-bodied Atlantic Forest mammalswhich were then classed by morpho-ecological traits. We used a DefaunationIndex, which was scaled-up to the entire biomeusing kriging interpolation, to examine the integrity of site-specific mammalfaunas. We further use environmental and socioeconomic predictors to explain the drivers of defaunation. Our results show high levels of defaunation(>0.5) for most of the Atlantic Forest. Apex predators, other carnivores, large-bodied mammalsand large herbivores were among the most defaunatedfunctional groups. Remaining native vegetation cover, forest fragmentsize, and the largest neighboring forest remnant were the main negative predictors of defaunation. We conclude that medium- to large-bodied Atlantic Forest mammalsare under high levels of threat due to historical population losses that continue today. A conservation action plan thus becomes imperative to prevent this biomefrom becoming an even “emptier forest”, severely compromising patterns of diversity, ecological processes and ecosystem functioning.