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The last 70 years have been good for corn production in the midwestern United States, with yields increasing five-fold since the 1940s. Much of this improvement has been attributed to advances in agricultural technology, but Harvard University researchers are wondering whether climate change and local temperature could play a bigger role than expected.
In a new article, the researchers found that a prolonged growing season due to rising temperatures, coupled with the natural cooling effects of vast plant fields, had largely contributed to the improved production of corn in the United States.
"Our research shows that improving crop yield depends in part on improving the climate," said Peter Huybers, professor of Earth and Planet Sciences at the Department of Earth Sciences and Geology. planets (EPS) and in environmental science and engineering at Harvard. John A. Paulson School of Engineering and Applied Science (SEAS). "In this case, temperature changes have had a beneficial impact on agricultural production, but there is no guarantee that this benefit will last as long as the climate changes." Understanding the detailed relationship between climate and crop yield is important to as we move forward on a changing planet. "
The research is published in the Proceedings of the National Academy of Sciences (PNAS).
The researchers modeled the relationship between temperature and crop yield from 1981 to 2017 in the so-called corn belt: Illinois, Indiana, Iowa, Kansas, Kentucky, the United States, and the United States. Michigan, Minnesota, Missouri, Nebraska, Ohio, South Dakota and Wisconsin. They found that as temperatures rose due to global climate change, planting days were getting older and earlier, moving about three days per decade.
"One of the most important decisions of farmers is to know what they are planting and when they plant it," said Ethan Butler, the newspaper's first author and former graduate student of EPS. "We are finding that farmers are planting earlier, not only because they have stronger seeds and better planting material, but also because it's getting warmer sooner."
Butler is currently a Postdoctoral Fellow in the Department of Forest Resources at the University of Minnesota.
Early planting means that corn has more time to mature before the end of the growing season.
There is also a second, more surprising trend that has benefited maize yields. While the vast majority of temperatures have warmed over the past century, the hottest days of the Midwest's growing season have actually cooled.
"Increasingly productive and high planting crops can evaporate more water from the leaves and soil during hot days," said Nathaniel Mueller, a former postdoctoral fellow at the Center for the Environment. Harvard University and co-author of the paper. "The widespread increases in evaporation rates apparently help to protect the corn from extreme heat, cool the surrounding area and increase yields."
Mueller is currently Assistant Professor in Earth System Science at the University of California at Irvine.
Researchers estimate that more than a quarter of the increase in crop yield since 1981 can be attributed to the twin effects of a longer growing season and lower exposure to high temperatures, suggesting that crop yields are more vulnerable to climate change than previously thought.
The researchers also showed that the planting and harvesting dates currently used by farmers are much better adapted to the current climate than to the climates of previous decades.
"Farmers are incredibly proactive and we see them taking advantage of temperature changes to improve their performance, and the question is how can they continue to adapt to future climate change," Huybers said.
Explore further:
Maize in a changing climate: the ability of crop adaptation can reduce the damage caused by global warming
More information:
Ethan E. Butler et al., "A particularly pleasant climate for American corn," PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1808035115
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