Dams not to blame for all reservoir carbon emissions from retained carbon

Dams trap organic carbon (OC) and create carbon dioxide (CO2) and methane (CH4) emission hotspots within reservoirs, underlying the ongoing debate over their role in carbon emissions. However, even without dams, this labile OC would still decompose and emit CO2 or CH4 during downstream transport and after deposition in estuaries, though the CH4production would be lower. Thus, relying solely on dammed reservoir observations to assess these emissions may introduce considerable bias. Here, we simulated both dammed and non-dammed scenarios for 5,346 global reservoir dams to assess their impact on carbon emissions from retained OC.