The study by Keijzer et al. (2024) assesses the global threats of dams to the persistence of freshwater fish species. Using a macroecological relationship between freshwater fish range size and body size, the authors evaluate whether isolated range fragments are too small to support viable populations. The analysis includes 7,369 freshwater fish species and considers 31,780 dams globally. The results show that over half of the analyzed species face potential extirpation in part of their geographic range, with an average potential range loss of 3.3%. For 74 species, more than 50% of their range is potentially lost, including 18 species threatened with extinction across their entire range. The study also highlights the additional impact of small dams compared to large dams, with a factor of 2–4 increase in potentially lost range. The findings identify species at risk of extirpation and geographic hotspots of threat, aiding in the development of strategies for hydropower development and barrier removal to balance biodiversity conservation and socio-economic benefits.The study by Keijzer et al. (2024) assesses the global threats of dams to the persistence of freshwater fish species. Using a macroecological relationship between freshwater fish range size and body size, the authors evaluate whether isolated range fragments are too small to support viable populations. The analysis includes 7,369 freshwater fish species and considers 31,780 dams globally. The results show that over half of the analyzed species face potential extirpation in part of their geographic range, with an average potential range loss of 3.3%. For 74 species, more than 50% of their range is potentially lost, including 18 species threatened with extinction across their entire range. The study also highlights the additional impact of small dams compared to large dams, with a factor of 2–4 increase in potentially lost range. The findings identify species at risk of extirpation and geographic hotspots of threat, aiding in the development of strategies for hydropower development and barrier removal to balance biodiversity conservation and socio-economic benefits.