Freshwater biodiversity impacts of global hydropower dams

Hydropower expansion creates tension between renewable energy goals and freshwater ecosystem health. However, the global impacts of dams across the full spectrum of freshwater biodiversity remain poorly quantified. Here, we combine remote sensing and global threatened species datasets to assess dam-related risk patterns for fish, mollusks, mammals, odonates, and amphibians. We show that threatened freshwater species are consistently more common near dams than elsewhere, with mammals showing the highest exposure. Most species whose risk status changed between 1996 and 2022 shifted toward higher threat levels in dam-influenced areas affected by habitat loss and reduced river connectivity. Planned future dams, concentrated in Global South countries, may further elevate extinction risk, particularly for critically endangered fish. These findings support sustainable planning that balances energy development with freshwater conservation.