Impacts of Pleistocene extinctions on the biomass and energy use of local mammal assemblages around the world

Many of the world's megafaunal species went extinct during the late Quaternary, leading to dramatic reductions in community and ecosystem functioning. While the nature and severity of the extinctions are well documented on global and continental scales, less is known about local-scale impacts. We quantified the biomass and energy use of 292 pre-extinction and 360 post-extinction fossil assemblages from around the globe to determine effects on large mammal communities. Assemblage energy use was calculated from metabolic rates obtained for 562 individual species, and was compared to species richness along with indicators of taphonomy, archaeology, and biogeography, using three analytical methods: least-squares orthogonalization regression, spatial autoregression, and linear mixed effects model analysis. Globally, total biomass and energy use are greatly reduced in post-extinction assemblages. Human-accumulated assemblages are further homogenised post-extinction due to their high abundances of domesticated species. The presence of domesticates greatly altered the biomass and energy use of assemblages post-extinction, producing strong energetic variation across continents that differs considerably to pre-extinction patterns. This fundamental anthropogenic alteration of communities further exacerbated the impacts of Pleistocene extinctions, even in less severely impacted regions. The results show how human activities have altered mammalian communities for many thousands of years.