From UC Berkeley Department of Environmental Science, Policy, and Management:
For over a century, agricultural scientists have sought to unravel the complex relationship between temperature and crop yields. Previous studies have found that yields for staple crops like maize and soybeans tend to increase as the temperature rises—that is, until the temperature passes 89.6 degrees Fahrenheit, at which point crop yields come crashing down.
A new study led by Assistant Professor Lucas Vargas Zeppetello suggests that the amount of water in soil has the strongest influence on crop yields, and can actually explain the high-temperature growing conditions that scientists have observed in agricultural areas. The findings, which are freely available online and will be published in the August issue of AGU Advances, may help farmers better manage agricultural production in a hotter world.
“We’ve known for a long time that high temperatures are associated with low yields, but we didn’t know why,” said Vargas Zeppetello, a faculty member in the Department of Environmental Science, Policy, and Management. “The goal of this work was to understand why crop yields decrease dramatically at high temperatures, and what this means for global climate change and the future of agriculture.”
Vargas Zeppetello and collaborators from Harvard University and the University of British Columbia used a physical model to simulate how soil moisture and temperature jointly influence crop yields. The authors reproduced the steep drop in crop yields when simulating temperature increases in rain-fed maize and soybean fields, and without considering any of the biological temperature dependencies included in previous models. After incorporating 2 millimeters of irrigation water per day into the model, the authors were able to virtually eliminate the decline in crop yields. Together, these findings suggest that soil moisture, rather than temperature, is the ultimate control on crop productivity in the historical record.
The findings suggest that uncertain rainfall projections make it more difficult for scientists to model the impact of climate change on the global food system. Managing our limited water resources, not just adapting agriculture to high temperatures, is vital for ensuring long-term food security.
“Projections that are based on temperature alone and show 50 to 80 percent yield losses by 2100 are, in my opinion, pretty unrealistic,” Vargas Zeppetello says. “But uncertainty in future rainfall patterns makes it very difficult to predict when and where agricultural regions will be impacted by climate change.”
Read the full study online in AGU Advances.
