Drought and human pressures contribute to persistent changes in freshwater invertebrate communities

•Freshwater ecosystems are threatened by increasing climate extremes including drought, which interacts with human pressures to drive biodiversity loss across spatial scales. River communities are considered resilient to droughts, but this characterization is based on short‐term, small‐scale studies. Moreover, drought resilience is increasingly compromised by human pressures.
•We used an unprecedented long‐term, large‐scale dataset spanning 359 perennial and near‐perennial river sites in south England sampled over 8–30 years to characterize ecological responses to multiple droughts and interacting human pressures, during a period of improving water quality. We determined how drought characteristics (including duration, magnitude, frequency, and spatial extent) and human pressures (including flow alteration and water quality) interact to influence aquatic invertebrate community resistance and resilience to droughts, including identification of persistent shifts in community composition.
•Although communities recovered on average within 1.5 years after 83% of droughts, those at 47% of sites experienced ≥ 1 long‐term, drought‐related compositional shift, challenging the paradigm of their resilience. Persistent shifts increased with drought duration and decreased with drought frequency, while anthropogenic flow reductions and lower oxygen concentrations altered community resistance and resilience to drought. Communities also experienced temporal drift (i.e., gradual compositional change) concurrent with improvements in water quality, and shifts were similarly frequent in drought and non‐drought periods.
•Pollution‐sensitive taxa often characterized communities following drought, indicating that these disturbance events can reset communities, allowing sensitive taxa to benefit from improved water quality. Our results also confirm the key effect of drought severity and frequency on long‐term community responses and the impacts of water abstraction and pollution on these responses.
•As drought severity increases in many global regions, our results could inform management actions that mitigate the ecological impacts of droughts in rivers exposed to multiple pressures.