Barb Boustead vividly recalls her introduction to the phenomenon known as corn sweat when she relocated to Nebraska two decades ago. Boustead moved to work for the National Oceanic and Atmospheric Administration and found herself immersed in a sea of cornfields. The term refers to the late-summer spike in humidity caused by corn plants releasing moisture as they cool themselves, a concept well-known among local residents, Boustead, a meteorologist and climatologist, remembered.
This characteristic of Midwestern summers could become even stickier due to climate change and the relentless advance of industrial agriculture. Rising temperatures and warmer nights are allowing the atmosphere to hold more moisture. Additionally, altered growing conditions now enable farmers to plant corn further north, increasing the overall corn acreage in the United States.
Farmers have been cultivating more corn to meet the soaring demand for ethanol, according to the USDA’s Economic Research Service. Consequently, more corn plants are working overtime to stay cool, emitting humidity that contributes to the oppressive heatwaves currently engulfing much of the U.S.
This phenomenon is especially pronounced in the Midwest, due to its vast expanses of cornfields. The plants reach the evapotranspiration stage concurrently, resulting in a significant and noticeable surge in humidity, Boustead explained. Evapotranspiration is the process wherein plants absorb water from the soil, utilize it for growth, and then release it as vapor into the air.
Dennis Todey, director of the U.S. Department of Agriculture’s Midwest Climate Hub, focuses on assisting producers with adapting to climate change. He noted that corn undergoes most of its evapotranspiration in July, rather than August. Soybeans, on the other hand, release more vapor than corn during August.
Todey emphasized that further research is necessary to fully grasp how climate change will impact corn sweat, pointing out that factors such as rainfall, crop varieties, and growing techniques all play a role.
Lew Ziska, an associate professor of environmental health sciences at Columbia University, has extensively studied the effects of climate change on crops. He confirms that warmer conditions inevitably lead to increased transpiration in plants. When asked whether more corn sweat is a consequence of climate change, his response was unequivocal: “Yes.”
Ziska also highlighted the growing demand for corn-based ethanol. More than 40% of the corn grown in the U.S. is converted into biofuels, which end up fueling cars and occasionally planes. The global production of ethanol has been climbing steadily, except for a decline during the COVID-19 pandemic, as reported by the Renewable Fuels Association.
Consumption of ethanol contributes to greenhouse gas emissions, compounding the problem. “It shouldn’t come as a surprise to anyone that it’s been getting hotter. And as a result of it getting hotter, plants are losing more water,” Ziska remarked.
