Midwest heat waves can cook crops and fry crops


Unstressed (left) and water-stressed (right) maize crops

Courtesy of Water Management Research Unit

On Adam Jones’ 750-acre farm in central Missouri, the corn is ripening and the soybean pods are plumping. But last summer was particularly hot, says the fourth-generation farmer, and that doesn’t bode well for this fall’s bounty. In July, temperatures soared above 90 degrees Fahrenheit for more than a week, with a heat index above 100. Then came the rain. At the end of the month, 11 inches of rain fell on Jones’ farm in less than 24 hours, flooding his fields. When it comes to the weather, he says, “there’s no more normalcy.”

With higher temperatures and changing precipitation patterns, climate change has been affecting America’s breadbasket for some time now. Ten years ago, the Midwest experienced its worst drought and heat stress in 50 years. The impact affected almost 80% of the region’s farmland, severely strained livestock production and increased food prices around the world. And the weird weather hasn’t calmed down since.

Climate scientists say extreme weather events are already happening more often than expected, and conditions like those seen in the Midwest over the past decade will only repeat themselves with more frequency as the climate continues to warm.

“I think everyone was surprised by the predictions that extreme events will become more common,” says Steve Long, a plant biologist at the University of Illinois. “But I think it happened on a scale that no one really expected.”

Longer droughts, as well as deluges that flood fields over shorter periods, can have devastating effects on crop yields. But researchers are also studying how heat waves could cause crops to sizzle.

A farmer pulls weeds from a field at Coneflower Farm in Tiskilwa, Illinois.

Daniel Acker/Bloomberg via Getty Images

The Extreme Heat Belt

The National Weather Service classifies days with heat indices of 125 degrees and above as “extreme danger,” or when the risk of heatstroke is very likely. A recent report released by the First Street Foundation, a nonprofit dedicated to quantifying and communicating climate risk, warns that 50 US counties could experience heat indexes of 125 degrees Fahrenheit in 2023. But over the next three decades , such heat is expected to occur in 1,023 counties, collectively home to nearly 108 million people. Dubbed the “extreme heat belt,” this vast swath of the country stretches from northern Texas and Louisiana through Illinois and Indiana and as far north as Wisconsin.

Such high heat indices would be an immediate health issue for farm workers (and anyone else without access to air conditioning). Such extremes also wreak havoc on the plants and animals that provide us with food and sustain rural economies.

The federal crop insurance program exists to help farmers manage the risks posed by extreme events. When wind, rain, heat or drought ravages their crops, farmers who take out a policy receive compensation. Claire O’Connor, NRDC’s director of water and agriculture, points out that from 2006 to 2010, the program cost an average of $5.1 billion a year. But from 2012 to 2016, the annual cost rose to $9.2 billion.

More and more farmers are using it, and a lot of that is due to the extreme weather events we’re seeing,” she says. O’Connnor and his team worked in the Midwest on policies that would give farmers a “good driver discount” on their insurance if they farm in a way that makes their crops more climate-resistant. If passed, the COVER Act, introduced in the House this summer, would deduct $5 per acre from farmers who plant cover crops and allow the United States Department of Agriculture (USDA) to explore rebates for other practices, such as composting and crop rotation.

Scientists Carl Bernacchi (left), Don Ort (center) and Lisa Ainsworth (right) in a plot of soybeans treated with high carbon dioxide at the SoyFACE Global Change Research Facility at the University of illinois

Institute of Genomic Biology/University of Illinois via USDA

Heat stress and crop yields

At the University of Illinois, plant biologist Carl Bernacchi is turning up the heat. On experimental plots, he simulates heat waves with an array of infrared lights and measures their effects on corn and soybeans.

At first, researchers thought that as the climate warmed and carbon dioxide concentrations increased in the atmosphere, plants would grow faster and become more productive, “but we actually see the opposite in most plants.” years,” says Bernacchi, who also works for the USDA. . Higher temperatures appear to interfere with photosynthesis and result in lower biomass and yield.

Early in the season, when Bernacchi brought on a heat wave — 12 degrees Fahrenheit hotter than average for this time of year — the plants did well. When he did the same during their breeding phase, however, yields declined.

“For each day of heat wave, you see a proportional decrease in yield,” he says. So if a plant typically goes through a 30-day reproductive development phase and experiences three days of extreme heat during that time, a farmer will see a 10% yield drop. Further evidence of the discovery may surface this year when corn growers in the region report their yields after such a hot summer.

Heat waves and warmer temperatures in general affect agriculture in other ways, but they’re not all bad. When they occur more often and earlier in the year, they can speed up the reproductive cycle of crops. This scenario could result in farmers growing multiple crop cycles in the summer. This could be a boon for production, as long as severe spring storms don’t prevent them from going into the fields, delaying planting or destroying seeds already sown. Recent research shows that over the past seven decades, approximately 43% of spring floods have caused crop losses.

Warmer temperatures also evaporate more moisture in the soil and plants. This adds water vapor to the surrounding air and can help keep temperatures from being as high locally as they are outside a sea of ​​agricultural fields. But hot weather also dries out the land, which can lead to and worsen drought, creating a situation where crops no longer have the moisture they need. Even though the surface temperature is cooler due to agriculture, plants remain susceptible to the impacts of heat waves, which can reduce farmers’ yields.

While Bernacchi’s results in Illinois may not apply to the entire Midwest, his ultimate goal is to collect data that will inform crop yield patterns as the climate continues to change. He’s now experimenting with adding moisture to the areas he’s studying, which the models don’t currently account for. “We can do the same experiments in growth chambers and greenhouses, but both are very far from field conditions,” he says.

Soybeans are unloaded onto a truck in Tiskilwa, Illinois.

Daniel Acker/Bloomberg via Getty Images

Local fields, global consequences

Various agricultural technologies have resulted in increased corn and soybean harvests over the past three decades. On the Jones farm, for example, yields have increased by about 10% in 10 years. Jones’ plants cover crops, which help sequester carbon and maintain moisture in the soil, but even so he expects future harvests to be smaller when summers get as hot as they come. were this year.

And what happens in the Midwest doesn’t always stay in the Midwest. Agricultural covers 127 million acres of the region, with corn and soy growing on 75% of them. These fields provide more than 33% of the world’s corn and 34% of the world’s soybeans, most of which is processed into meal for livestock. A heat wave here can contribute to food shortages in the global market and add to other climate-related supply problems that may occur elsewhere. Extreme weather conditions are affecting agriculture around the world, with maize yields, for example, should decrease by more than 20 percent by 2070. Livestock are also likely to suffer, as was the case in Kansas last June when 2,000 cattle died in temperatures exceeding 100 degrees. (Some farmers put up sheds to provide shade for their animals and change the bedding in the pens to keep the ground from getting too hot.)

Learning to adapt to extreme heat is critically important to the global food supply and the health of farm workers. And you don’t have to look far to see the interconnections between climate, food scarcity and political stability. For example, “the Arab Spring was closely linked to food shortages in North Africa and the Middle East,” Long says. The pro-democracy upheaval was sparked just over a decade ago, in part by extreme weather – from floods in Australia to yellow dust storms in the Middle East – which destroyed crops and caused food shortages. With soaring wheat prices, bread, a regional staple, has become prohibitively expensive.

There’s no reason to think that future heat waves in grain-growing regions of the world wouldn’t aggravate other social pain points or create new instabilities, Long says. “We should worry globally as well as locally.”

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