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

After baseline correction in simulations of 5,346 global reservoir dams, dams increase retained-OC carbon emissions by an average of 21.5% CO2-eq, not the larger reservoir-only estimates.

• Why it matters: Dammed-reservoir observations can bias assessments because labile organic carbon would still emit CO2 or CH4 under no-dam conditions during downstream transport and after estuarine deposition.
• What they did: The study simulated dammed and non-dammed scenarios for 5,346 global reservoir dams and used XGBoost to identify controls, highlighting reservoir depth and hydraulic residence time.
• The result: Reservoir-only approaches overestimate dam-induced emissions by ignoring baseline no-dam emissions; after correction, dams account for 18.6% of conventional reservoir-based accounting estimates.