Hotspots of irrigation-related US greenhouse gas emissions from multiple sources

Abstract

Irrigation effectively increases yields and buffers against intensifying climatic stressors to crop productivity but also produces greenhouse gas (GHG) emissions through several pathways including energy use for pumping (on farm and for interbasin water transfers), N2O emissions from increased denitrification under elevated soil moisture, and degassing of groundwater supersaturated in CO2. Despite irrigation’s climate adaptation potential, associated GHG emissions remain unquantified. Here we conduct a comprehensive, county-level assessment of US GHG emissions from these irrigation-related pathways, estimating that irrigation produces 18.9 MtCO2e annually (95% confidence interval 15.2–23.5 Mt), with 12.6 Mt from on-farm pumping, 1.1 Mt from pumping for interbasin transfers, 2.9 Mt from elevated N2O and 2.4 Mt from groundwater degassing. These emissions are highly spatially concentrated, revealing opportunities for geographically targeted and source-specific GHG mitigation actions. These findings enable strategic consideration of GHG emissions in decision-making associated with irrigation expansion for climate adaptation. Despite its utility for climate change adaptation, US irrigation produces 18.9 MtCO2e yr−1 from groundwater degassing, elevated N2O and energy use. This county-level analysis reveals opportunities for geographically targeted emissions mitigation.