A new study by an international team of researchers shows how irrigation affects regional climates and environments around the world, illuminating how and where the practice is both untenable and beneficial.
The analysis, which appears in the journal Nature Reviews Earth and Environment, also points to ways to improve assessments in order to achieve sustainable water use and food production in the future.
“Even though irrigation covers a small fraction of the earth, it has a significant impact on regional climate and environments—and is either already unsustainable, or verging on towards scarcity, in some parts of the world,” explains Sonali Shukla McDermid, an associate professor in NYU’s Department of Environmental Studies and the paper’s lead author. “But because irrigation supplies 40% of the world’s food, we need to understand the complexities of its effects so we can reap its benefits while reducing negative consequences.”
Irrigation, which is primarily used for agricultural purposes, accounts for roughly 70% of global freshwater extractions from lakes, rivers, and other sources, amounting to 90% of the world’s water usage. Previous estimates suggest that more than 3.6 million square kilometers —or just under 1.4 million square miles—of the earth’s land are currently irrigated. Several regions, including the US High Plains states, such as Kansas and Nebraska, California’s Central Valley, the Indo-Gangetic Basin spanning several South Asian countries, and northeastern China, are the world’s most extensively irrigated and also display among the strongest irrigation impacts on the climate and environment.
While work exists to document some impacts of irrigation on specific localities or regions, it’s been less clear if there are consistent and strong climate and environmental impacts across global irrigated areas—both now and in the future.
To address this, a total of 38 researchers from the US, Australia, Austria, Belgium, France, India, Italy, Japan, South Korea, and Taiwan analyzed more than 200 previous studies—an examination that captured both present-day effects and projected future impacts.