Climate Factors Amplifying the Impact of Low‐Head Dams on Riverine Biodiversity Based on a Meta‐Analysis

ABSTRACT River regulation by dams is considered a major threat to river biodiversity, including that of benthic algae, macroinvertebrates, and fish, due to alterations in river hydrological regimes. However, it remains unclear how annual air temperature and precipitation influence the effects of low‐head dams on the biodiversity of various river biomes. This review conducted a meta‐analysis of studies that quantify the impacts of low‐head dams in relation to annual temperature and precipitation on riverine biodiversity. We extracted estimates of the impacts of dams on the richness and Shannon‐Weiner diversity index of river biomes (i.e., fish, macroinvertebrates, and benthic algae) from 79 case studies. We found a significant increase in Shannon–Wiener diversity downstream of diversion outlets. The annual average temperature significantly increased the effect size of species richness both upstream of the dam and downstream of the outlets, as indicated by positive correlations derived from mixed‐effect models. Furthermore, both annual average temperature and annual precipitation significantly amplified the effect size of the Shannon–Wiener diversity index downstream of the outlet. Our review reveals the significant impacts of dams on riverine biodiversity and highlights the crucial role of climatic factors in understanding the effects of hydropower and dam construction on aquatic ecosystems.