A team of researchers from Cornell University has weighed in on a high-stakes debate between crop experts and scientists, and they concluded that climate change-induced heat stress would play a more significant role than drought stress in reducing the yields of several major U.S. crops later this century.

An assistant professor of applied economics and management, Ariel Ortiz-Bobea, said that there is a big divide in this field, and they thought there must be some way to resolve this puzzle. That has significant implications for crop management as well as plant breeding.

With the use of decades' worth of data from government and other sources, the researchers published their results in Environmental Research Letters. Among researchers that contributed to the study included Toby Ault, assistant professor of earth and atmospheric science, postdoctoral associate Carlos Carrillo, and Haoying Wang, assistant professor of management at New Mexico Tech.

Ortiz-Bobea and his colleagues incorporated information from three sources to develop a statistical crop yield model for six crops that include maize, cotton, sorghum, soybeans, spring wheat, and winter wheat.

The analysis of the team showed that soil moisture alone was the best predictor of year-to-year variations in yield across the past four decades. Harvests were particularly sensitive to drought stress in the middle portion of the growing season.

Next, the researchers applied their statistical model to climate change scenarios ranging from mild to severe. The analysis projects that temperature which the authors interpret as heat stress will be the primary climate driver of crop yield in 2050 and 2100. Under the mildest scenario, returns for the six crops are predicted to decrease by 8 percent to 19 percent, relative to a world without climate change. Under the most severe scenario, the projected yield reductions range from 20 percent to 48 percent.

They forecasted the most considerable losses for maize and spring wheat, but more resilient crops such as sorghum, which is half as sensitive to high temperature as maize, will experience less damage.

As noted by the co-author of the study, Ault said that climate change projections show that many of the food-producing counties in the United States could become drier in the summer even if rainfall increases. In a changing climate, this situation could motivate farmers to plant earlier, but that approach to adaptation can be thwarted by heavy rains during the late spring, as many regions are experiencing this year.

Ault noted further that the work highlights two significant challenges for adapting to a changing climate. First, how do we deal with increases in temperature that through higher evaporation could surpass increases in precipitation? The second challenge is how we can start to envision an agricultural system of the 21st century that is equipped to handle the remarkable shifts in the seasonality that might occur?