Biotic Homogenization Destabilizes Ecosystem Functioning By Decreasing Spatial Asynchrony

Our planet is facing significant changes of biodiversity across spatial scales. Although the negative effects of local biodiversity (alpha diversity) loss on ecosystem stability are well documented, the consequences of biodiversity changes at larger spatial scales, in particular biotic homogenization, that is, reduced species turnover across space (beta diversity), remain poorly known. Using data from 39 grassland biodiversity experiments, we examine the effects of beta diversity on the stability of simulated landscapes while controlling for potentially confounding biotic and abiotic factors. Our results show that higher beta diversity generates more asynchronous dynamics among local communities and thereby contributes to the stability of ecosystem productivity at larger spatial scales. We further quantify the relative contributions of alpha and beta diversity to ecosystem stability and find a relatively stronger effect of alpha diversity, possibly due to the limited spatial scale of our experiments. The stabilizing effects of both alpha and beta diversity lead to a positive diversity-stability relationship at the landscape scale. Our findings demonstrate the destabilizing effect of biotic homogenization and suggest that biodiversity should be conserved at multiple spatial scales to maintain the stability of ecosystem functions and services.