The number is almost too big to wrap your head around: 363. That is roughly how many times more greenhouse gas emissions the United States would release if farmers suddenly stopped irrigating their crops. New research from Colorado State University (CSU) shows that pumping water onto fields—far from being an environmental problem—actually keeps the planet cooler than the alternative. Because irrigation lets farmers grow more food on less land, it spares millions of acres of wild places from being plowed up for agriculture. And that matters: whenever a forest or grassland is cleared for farming, the carbon stored in its soil and plants escapes into the air.
Here is the logic, explained simply. Without irrigation, farms in dry parts of the country would produce much less food. To make up for those lost harvests, people would need to convert huge stretches of natural land into new farmland. That land conversion would release enormous amounts of trapped carbon. The CSU team, led by Avery Driscoll, worked out that the emissions saved by avoiding this land-use change are 363 times greater than the emissions irrigation itself causes. Those avoided emissions add up to 6.86 gigatons—more than the entire United States emitted in all of 2024, and roughly 13% of total global emissions that year.
The study, published in the journal Proceedings of the National Academy of Sciences, is the first to compare both the direct and indirect greenhouse gas effects of irrigation. The direct costs come mostly from the energy used to pump water, both on farms and across river basins. The indirect benefit is the land that gets saved. "It was clear from this work that irrigation has a net positive effect on emissions," said Driscoll, who began the research as a CSU Ph.D. student and is now a postdoctoral researcher at Purdue University.
The best news? The biggest part of irrigation's own footprint is also the easiest to fix. Most emissions come from fossil-fuel pumps, and swapping them for electric ones—especially as the electricity grid gets cleaner—could shrink that footprint further. The researchers suggest policymakers consider incentives for pump electrification in climate-smart agriculture programs. "Ideally, this is a win-win for addressing local emissions and also harnessing the global benefits of irrigation," Driscoll said.
To reach these numbers, the team mapped crop yields county by county across the U.S., then used an economic model to see how much extra land would be farmed if all crops depended only on rain. Co-author Nathan Mueller, a CSU associate professor, stressed that the work is "one piece of the puzzle" in bigger debates about water use, especially in the water-stressed western U.S. "There are trade-offs with every use," he said. "Yet we're able to show this large benefit of U.S. irrigation." The message for policymakers: when it comes to climate, how we use water and how we use land are two sides of the same coin.