Understanding the effects of climate change on biological communities and ecosystem functioning represents a major challenge in global biodiversity conservation. This is particularly true in riverine systems, where changes in flow regimes are expected to compound the impact of warming on biota. Beyond climate change, other human disturbances also affect species dynamics, hence making it difficult to disentangle the role of climate change from other anthropogenic stressors in biodiversity responses. Here, we tested for a global imprint of recent climate change on riverine fishes by compiling and analysing a global dataset of community abundance time series. To do so, we used species-specific water temperature and flow affinities to detect signatures of tropicalization (warm-water) and lentification (slow-flow) of fish communities. We then related these changes in community composition to temporal trends in water temperature and flow regime and assessed whether alterations in land cover amplified or attenuated the effects of climate change on riverine biodiversity.
Results/Conclusions
Overall, we found that community trends are consistent with our predictions, indicating that climate change has already driven widespread community reorganization in riverine systems. Fish communities have seen an increase in the prevalence and abundance of warm-water and lentic species, notably in areas most affected by climate and land use changes. However, the climate change signal is variable across river basins and climatic zones, reflecting to some extent the availability of temporally and spatially intensive datasets. Taken together, our results highlight the complex responses of biological communities to recent changes in climate and they call for greater monitoring efforts to better inform the management of freshwater resources.