Predicting ecosystem stability from community composition and biodiversity

As biodiversity is declining at an unprecedented rate, an important current scientific challenge is to understandand predict the consequences of biodiversity loss. Here, we develop a theory that predicts the temporalvariability of community biomass from the properties of individual component species in monoculture.Our theory shows that biodiversity stabilises ecosystems through three main mechanisms: (1) asynchrony inspecies’ responses to environmental fluctuations, (2) reduced demographic stochasticity due to overyieldingin species mixtures and (3) reduced observation error (including spatial and sampling variability). Parameterisedwith empirical data from four long-term grassland biodiversity experiments, our prediction explained22–75% of the observed variability, and captured much of the effect of species richness. Richness stabilisedcommunities mainly by increasing community biomass and reducing the strength of demographic stochasticity.Our approach calls for a re-evaluation of the mechanisms explaining the effects of biodiversity onecosystem stability.