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Food securityClimate change to deplete some U.S. water basins, reduce irrigated crop yields

By Jennifer Chu

Published 17 July 2017

A new study by MIT climate scientists, economists, and agriculture experts finds that certain hotspots in the country will experience severe reductions in crop yields by 2050, due to climate change’s impact on irrigation. The most adversely affected region, according to the researchers, will be the Southwest. Already a water-stressed part of the country, this region is projected to experience reduced precipitation by midcentury. Less rainfall to the area will mean reduced runoff into water basins that feed irrigated fields.

A new study by MIT climate scientists, economists, and agriculture experts finds that certain hotspots in the country will experience severe reductions in crop yields by 2050, due to climate change’s impact on irrigation.

The most adversely affected region, according to the researchers, will be the Southwest. Already a water-stressed part of the country, this region is projected to experience reduced precipitation by midcentury. Less rainfall to the area will mean reduced runoff into water basins that feed irrigated fields.

Production of cotton, the primary irrigated crop in the Southwest and in southern Arizona in particular, will drop to less than 10 percent of the crop yield under optimal irrigation conditions, the study projects. Similarly, maize grown in Utah, now only yielding 40 percent of the optimal expected yield, will decrease to 10 percent with further climate-driven water deficits.

In the Northwest, water shortages to the Great Basin region will lead to large reductions in irrigated forage, such as hay, grasses, and other crops grown to feed livestock. In contrast, the researchers predict a decrease in water stress for irrigation in the southern Plains, which will lead to greater yields of irrigated sorghum and soybean.

If efforts are made to reduce greenhouse gases and mitigate climate change, the researchers find that water scarcity and its associated reductions in cotton and forage can be avoided.

“In the Southwest, water availability for irrigation is already a concern,” says first author Elodie Blanc, a research scientist at MIT’s Joint Program on the Science and Policy of Global Change. “If we mitigate, this could prevent added stress associated with climate change and a severe decrease in runoff in the western United States. But it will be even worse in the future if we don’t do anything at all.”

Blanc’s study appears in the journal Earth’s Future, and her co-authors are Erwan Monier, a principal research scientist at MIT; Justin Caron, an assistant professor at HEC Montreal; and Charles Fant, a former MIT postdoc.

“A more integrated world”
While many researchers have investigated the effects of climate change on crop yields, Blanc’s study is one of the first to consider how a changing climate may shape the availability and distribution of water basins on which irrigated crops depend.