Plant diversity is known to enhance ecosystem productivity however, whether biodiversity effects on productivity intensify during climate extremes, and the environments and ecosystem types that show the strongest biodiversity effects have not been clarified. Filling this knowledge gap has become increasingly urgent as droughts and heatwaves intensify worldwide. Although biodiversity effects have been predicted to strengthen under environmental stress empirical evidence remains fragmented. Previous studies have shown that biodiversity can enhance ecosystem resistance under climate extremes in global grasslands and promote ecosystem functioning under a range of experimental stressors across taxa.
A key barrier to resolving how biodiversity–productivity relationships shift across environmental contexts during climate extremes is the restricted geographic and temporal scope of most experiments and observational datasets. These constraints prevent a better understanding of the diverse environmental contexts and extreme climatic events that modulate biodiversity effects across sites. Recent global syntheses have facilitated important progress and shown that biodiversity effects on productivity increase with community age and are generally stronger in grassland and forest ecosystems than in agricultural or aquatic systems. However, these syntheses have also reported relatively consistent biodiversity effects across spatial climate gradients and limited sensitivity to interannual climatic variability. Thus, the contexts under which biodiversity can buffer productivity under climate extremes remain unresolved
