Local diversity, beta diversity and climate influence the regional stability of bird biomass across North America

Biodiversity often stabilizes aggregate ecosystem properties (e.g.,
biomass) at small spatial scales. However, the importance of species
diversity within communities and variation in species composition among
communities (β-diversity) for stability at larger scales remains unclear.
Using a continental-scale analysis of 1,657 North American breeding-bird
communities spanning 20-years and 35 ecoregions, we show local species
diversity and β-diversity influence two components of regional stability:
local stability (stability of bird biomass within sites) and spatial
asynchrony (asynchronous fluctuations in biomass among sites). We found
spatial asynchrony explained three times more variation in regional
stability of bird biomass than did local stability. This result contrasts
with studies at smaller spatial scales – typically plant metacommunities
under 1 hectare – that find local stability to be more important than
spatial asynchrony. Moreover, spatial asynchrony of bird biomass increased
with bird β-diversity and climate heterogeneity (temperature and
precipitation), while local stability increased with species diversity.
Our study reveals new insights into the scale-dependent processes
regulating ecosystem stability, providing evidence that both local
biodiversity loss and homogenization can destabilize ecosystem processes
at biogeographic scales.