Aggregate gains and crop-driven trade-offs in the carbon and nitrogen footprints of China's interprovincial trade in rice, wheat and maize

China's grain production and consumption are spatially mismatched, but the joint carbon–nitrogen consequences of interprovincial trade bridging this mismatch remain unclear. We applied a carbon–nitrogen footprint framework to evaluate rice, wheat and maize bilateral trade among 31 Chinese provinces for ten selected observation years between 2000 and 2022. Local self-supply counterfactual scenario was used as an analytical baseline. Interprovincial trade reduced national production-stage greenhouse gas emissions and reactive nitrogen losses in all observation years. In 2022, reductions reached 35.7 Mt CO 2 -eq and 1.17 Mt N-eq, or 9.7% and 16.3% of local self-supply burdens, and remained positive in uncertainty analyses. All three crops contributed positively, with maize providing the largest share of both benefits—48.3% of the GHG reduction and 66.8% of the reactive-N reduction. Provincial outcomes diverged: seven provinces had opposing greenhouse gas and nitrogen effects in 2022, with rice-exporting provinces showing higher greenhouse gas but lower nitrogen burdens relative to local self-supply, and maize- or wheat-exporting provinces showing the reverse. China's interprovincial trade in rice, wheat and maize delivers aggregate gains while revealing crop-driven provincial trade-offs.