Effects of mammal defaunation on natural ecosystem services and human well being throughout the entire Neotropical realm

Mammals embody the apex of ecosystems processes, and their majestic diversity is overwhelmingly threatened in the Neotropical realm. Mammal population declines erode not only several levels of biological diversity, but may also impoverish critical ecosystem services (ES). Based on 2,427 putative baseline mammal assemblages derived from IUCN ranges polygons, we sought to understand, for the first time, the effects of mammal defaunation on natural ecosystem services throughout the entire Neotropical realm. At the assemblage-level, we simulated both stochastic and deterministic regimes of mammal defaunation, examining both diversity indices and classic metrics of ecological networks (e.g. modularity and nestedness). Our results show that ES losses are induced by declines in both taxonomic and functional diversity. Given any defaunation regime, Neotropical provinces undergo levels of ES erosion typically reaching less than a third of all potential network links. Geographic patterns of lost ecosystem services—resulting from simulated and real-world mammal extinctions—indicate that this will detrimentally affect human livelihoods across all major Neotropical provinces. We conclude that the ongoing defaunation process will promote irreversible failures of several mammal-mediated ecosystem processes at varying timescales.