Quantitative synthesis of the effects of drought on community composition and species interactions in terrestrial ecosystems

Droughts, increasingly frequent under human-driven climate change, are expected to intensify globally. Both pulsed and prolonged droughts can strongly affect organismal survival and population dynamics, potentially altering terrestrial communities and ecosystems. Understanding how drought influences communities is therefore critical for predicting and mitigating its impacts. Here, we conducted two meta-analyses that evaluate two components of communities: community composition and species interactions, revealing overall negative effects of drought in both analyses. By synthesizing experimental and observational studies across terrestrial ecosystems, we show that while drought consistently restructures community composition in ways that scale with severity and duration, its effects on species interactions are more heterogeneous and do not scale predictably, revealing a decoupling between community reorganization and interaction dynamics. In particular, we found negative effects on species richness, and on plant and arthropod community composition, and predation and decomposition were more likely to be negatively affected by drought. Drought's effects also varied among biomes: community composition was most altered in grasslands and boreal forests, whereas trophic interactions in forests consistently weakened under drought, reflected as reduced rates of predation, herbivore attack, and litter consumption. Although drought is expected to harm systems across taxa and biomes, we also identified cases where drought had no overall effect, suggesting the potential resilience of some communities and stability of certain trophic interactions. Overall, our meta-analyses demonstrate that drought can disrupt ecological communities on a global scale and underscores the importance of targeted monitoring of drought effects in terrestrial ecosystems, particularly in regions of high risk.