The core of the study focuses on the concept of indirect land-use change. If irrigation were suddenly eliminated, the United States would need to convert vast amounts of natural ecosystems into agricultural land to maintain current food production levels. This conversion would release significant amounts of carbon stored in soil and vegetation, leading to a massive spike in greenhouse gas emissions. The researchers estimate that the emissions saved by avoiding this land conversion equate to 363 years’ worth of today’s annual U.S. greenhouse gas emissions from irrigation. This staggering figure highlights the hidden climate cost of relying solely on rainfed agriculture in a growing global population.

Lead author Avery Driscoll, who conducted the research as a Ph.D. student at Colorado State University, emphasized the clarity of the findings. “It was clear from this work that irrigation has a net positive effect on emissions,” Driscoll stated. The avoided emissions from reductions in indirect land-use change were significantly greater than the direct emissions associated with pumping water. Furthermore, Driscoll noted that the net benefit could improve further with the electrification of irrigation pumps. By replacing fossil fuel-powered pumps with electric ones, the direct emissions component could be reduced, thereby increasing the overall climate benefit of irrigation systems.

The study identifies energy use as the primary source of direct emissions from irrigation. Pumping water for both on-farm use and interbasin transfers requires significant energy, which currently relies heavily on fossil fuels in many regions. However, the researchers argue that this is the most easily solvable part of the equation. They suggest that policymakers should consider incentives for electrification when developing climate-smart agriculture programs. Additionally, smaller amounts of nitrous oxide are released through microbial respiration, and dissolved carbon dioxide is dispersed when groundwater is sprayed on fields, but these contribute less to the total direct emissions compared to energy use.

To quantify the avoided emissions, the researchers developed a detailed model that mapped yield benefits at the county level across the United States. They calculated a ratio of rainfed to irrigated yields using existing survey data and a machine learning model. This allowed them to determine how much additional land would be required to produce the same amount of food without irrigation. The team then used a global economic model to simulate production, consumption, and trade flows, determining how U.S. production would change if it were entirely rainfed. This model accounted for the suitability of different crop types in various regions, providing a realistic estimate of the land-use changes that would occur in the absence of irrigation.

The estimated avoided emissions due to irrigation amount to 6.86 gigatons of carbon dioxide equivalent. This figure is more than the total annual emissions of the United States in 2024, which were 5.91 gigatons. It also represents about 13% of total global emissions for that year. These numbers underscore the significant role that U.S. irrigation plays in the global carbon cycle. By preventing the conversion of natural lands to agriculture, irrigation helps keep carbon locked in ecosystems, thereby mitigating the effects of climate change. The study demonstrates that climate-smart agricultural policies must consider both direct and indirect emissions impacts to fully understand the climate implications of water use.

Driscoll, now a postdoctoral researcher at Purdue University, highlighted the importance of a comprehensive approach to emissions accounting. “This comprehensive approach to accounting for direct emissions from the field and for the indirect land-use impacts lets us identify local opportunities to reduce emissions, through pump electrification and grid decarbonization, while also maximizing benefits associated with increasing productivity,” she said. This dual focus allows for a win-win scenario where local emissions are reduced, and the global benefits of irrigation are harnessed. The study provides a robust framework for understanding the trade-offs and synergies between food production and climate mitigation.

Co-author Nathan Mueller, a CSU associate professor in the departments of Ecosystem Science and Sustainability and Soil and Crop Sciences, noted that while the study shows a large benefit of U.S. irrigation to greenhouse gas emissions, there are trade-offs with every use of water. “When we talk about water use, particularly in the western U.S., there are trade-offs with every use and trade-offs beyond food and beyond greenhouse gas emissions,” Mueller said. He emphasized that the work provides one piece of the puzzle to help examine the complicated societal cost-benefit questions surrounding water use. The study does not account for other agricultural management practices that can lead to emissions, such as nitrogen application on crops or methane from livestock, but it offers a crucial insight into the role of irrigation in the food system.

The practical implications of the study are evident in the experiences of farmers like Alex Brown, a CSU alumnus whose family has been farming and ranching in Yuma County, Colorado, for 120 years. Brown stated, “We need irrigation to fulfill our needs and our duty to continue to feed the world.” He explained that without irrigation, farmers would have to plow up less productive and more ecologically sensitive pastureland for crops, making them dependent on unreliable rainfall. As the population increases, the demand for food and agriculture on less land also increases. Brown and other producers in Yuma County are committed to improving irrigation efficiency through technology and modern equipment, reflecting a broader trend toward sustainable water management in agriculture.

Driscoll concluded that irrigation is a powerful adaptation strategy that increases productivity and resilience to heat and drought stress. Maintaining and increasing agricultural production is a critical priority, especially in the face of climate change. At the same time, reducing food system emissions is essential for mitigating climate impacts. Understanding how these two challenges interact is a priority for researchers and policymakers. This work allows for a better grasp of the trade-offs and synergies involved, providing a foundation for developing policies that support both food security and climate goals. The study was funded by the National Science Foundation and the AI Institute for Land, Economy, Agriculture & Forestry, with collaborators from the University of Minnesota, U.S. Forest Service, University of Maine, and The Nature Conservancy.

Subject of Research: Climate impact of U.S. agricultural irrigation and land-use change

Article Title: Greenhouse gas benefits of ag irrigation outweigh emissions costs

Article References: Greenhouse gas benefits of ag irrigation outweigh emissions costs. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Agricultural Irrigation, Greenhouse Gas Emissions, Land-Use Change, Climate Change, Food Security, Water Management, Sustainable Agriculture, Carbon Sequestration, Energy Efficiency, Economic Modeling, Greenhouse, benefits