Assemblage Time Series Reveal Biodiversity Change but Not Systematic Loss

TLDR

Biodiversity change in local assemblages and its contribution to global loss remain poorly understood, underscoring the need to monitor species composition for conservation. The study examined 100 assemblage time series from biomes worldwide to determine how diversity within assemblages changes over time. The authors quantified temporal α diversity (local diversity change) and β diversity (community composition change) across the 100 time series. The analysis found no systematic loss of α diversity, but community composition changed systematically over time beyond null model predictions, possibly due to heterogeneous environmental change, climate‑driven range shifts, and biotic homogenization.

Abstract

The extent to which biodiversity change in local assemblages contributes to global biodiversity loss is poorly understood. We analyzed 100 time series from biomes across Earth to ask how diversity within assemblages is changing through time. We quantified patterns of temporal α diversity, measured as change in local diversity, and temporal β diversity, measured as change in community composition. Contrary to our expectations, we did not detect systematic loss of α diversity. However, community composition changed systematically through time, in excess of predictions from null models. Heterogeneous rates of environmental change, species range shifts associated with climate change, and biotic homogenization may explain the different patterns of temporal α and β diversity. Monitoring and understanding change in species composition should be a conservation priority.