Global Study Uncovers Key Stressors Driving River Biodiversity Decline

Freshwater ecosystems, particularly rivers, are experiencing the most rapid biodiversity declines of any biome, driven by several interacting stressors operating across local to global scales. Despite growing research on these interactions, the lack of systematic quantification of individual stressor gradients limits our ability to disentangle their cumulative effects.

To tackle this challenge, researchers presented a global synthesis of stressor-response relationships across five key riverine organism groups: prokaryotes, algae, macrophytes, invertebrates, and fish.

The study involved screening 22,120 papers and extracting 276 studies with 1,332 stressor-response relationships. Utilizing generalized linear mixed models and Bayesian meta-analyses, the team quantified the response to the seven most prevalent stressors.

The findings provided crucial insights. As lead author Kaijser notes in the paper, "Consistently across taxa, biodiversity loss (taxon richness and evenness) reflected elevated salinity, oxygen depletion and fine sediment accumulation, while the association with nutrient enrichment and warming varied among groups." Predictive tools, including hypothetical outcome plots and partial dependence plots, revealed the interplay of stressors and predicted biodiversity response to stress increase.

These findings establish a quantitative baseline for a continuous global synthesis, refining predictions of anthropogenic stressor impacts, identifying key research gaps and informing conservation strategies for freshwater ecosystems.