If all proposed hydropower dams were built, over 260,000 km of rivers, including the mainstems of the Amazon, Congo, Irrawaddy and Salween, would lose free-flowing status. The estimated hydropower generated by proposed dams on free-flowing rivers represents less than 2% of the projected worldwide renewable power needed by 2050 to keep warming below 1.5°C.
The authors set out a hierarchy of responses: avoid river fragmentation by exploring alternative development options, minimise impacts through strategic or system-scale planning, restore rivers through dam removal, and mitigate remaining impacts through biodiversity offsets.