Understanding why biodiversity stabilizes fluctuations in ecosystem properties (e.g. biomass) is a fundamental step for linking ecology and ecosystem sustainability. Biodiversity loss within local communities can destabilize emergent properties at small spatial scales. At larger spatial scales, stability also depends on the extent to which these properties fluctuate asynchronously across communities (spatial asynchrony). Recent theory suggests that spatial asynchrony can be generated by an interaction between dissimilar species compositions (β-diversity) and environmental heterogeneity. However, empirical evidence supporting this prediction is lacking; therefore, it remains unclear how variation in biodiversity and the abiotic environment across communities influences the stability of regional ecosystems. Using over 1,600 20-yr time series of breeding bird communities distributed across 32 regions in North America, we tested 1) the relative importance of local stability and spatial asynchrony in biomass for stabilizing regional bird biomass; 2) the importance of β-diversity for generating spatial asynchrony; and 3) the extent to which this importance depends on environmental heterogeneity.
Results/Conclusions
Asynchrony in biomass dynamics across communities explained most (64%) of the variation in regional ecosystem stability. Local stability also contributed to regional stability, but to a lesser degree (19%). The number of communities in a region, β-diversity, and within region variation in climate and precipitation all contributed to spatial asynchrony in bird biomass. Moreover, β-diversity—specifically species turnover—had a stronger influence on spatial asynchrony when environmental conditions were more homogeneous across communities. We provide the first empirical evidence that β-diversity and environmental heterogeneity interactively contribute to spatial asynchrony and the stability of regional ecosystems. Thus, global changes that reduce environmental heterogeneity will likely magnify the consequences of biodiversity loss for destabilizing regional ecosystems. Our findings suggest that in the face of uncertain global change, maintaining biodiversity across scales is necessary to ensure reliable ecosystem functions and services.