Irrigation's land-saving effect may offset its emissions by centuries
New research from Colorado State University finds that U.S. irrigation prevents far more greenhouse gas emissions than it produces by boosting crop yields and reducing the need to convert natural lands to farmland. If irrigation were eliminated, replacing lost production would require expanding farmland, releasing an estimated 6.86 gigatons of emissions—equivalent to 363 years of current irrigation emissions.
The study, published in Proceedings of the National Academy of Sciences, compared direct irrigation emissions—primarily from fossil fuel-powered water pumps—against the indirect benefit of avoiding land conversion. Natural ecosystems store significant carbon in vegetation and soils, and converting them to farmland releases that stored carbon. Agricultural land use accounts for nearly a quarter of global greenhouse gas emissions.
The researchers note that electrifying pumping systems could further reduce irrigation's direct emissions, especially as the power grid becomes cleaner. Earlier work by the team examined additional direct sources, including nitrous oxide from microbial activity and carbon dioxide dissolved in groundwater that escapes when sprayed on fields. This new analysis is the first to directly compare those emissions against the land-saving benefits.
This research could reshape how policymakers evaluate agricultural climate strategies. If irrigation's land-saving effect truly outweighs its emissions by centuries, programs that restrict water use for environmental reasons may need to weigh the indirect climate consequences of reduced yields. Farmers, water managers, and climate planners could all be affected by this more complete accounting, though the findings depend on assumptions about how lost production would be replaced.