Little girl walking through corn field

Growing Corn Is Changing The Climate

Excerpted from: Americans have planted so much corn that it’s changing the weather
Excerpted from: ‘Corn sweat’ is making the air in the Midwest oppressively muggy

During summer, the Midwest can experience some of the most oppressive humidity in the country. Fields in Iowa can be muggier than beaches in Miami. The culprit? Billions of stalks of corn.

  Corn Sweat and Climate Change

Akin to a person breathing, plants exhale water into the atmosphere through a process called evapotranspiration. Some call it corn sweat.

In the Midwest and northern Plains, corn and soybean crops draw moisture from the ground through their roots into their leaves, stems and fruits. The water evaporates into the surrounding air through their leaves, joining forces with neighboring water molecules to humidify the air.

This extra humidity is making the heat wave centered over the middle of the Lower 48 states even more oppressive.

The moisture from corn evapotranspiration may not only make it intolerably muggy during the day, it can also slow cooling at night, leaving little respite from the heat.

Data from the past 30 years has found that the intensification of corn production has increased average summer rainfalls by about 35% and decreased average summer temperatures by as much as 1° Celsius.

2018 MIT Climate Report

A 2018 report issued by climate researchers at the Massachusetts Institute of Technology claims to have solved the mystery and verified farmers’ suspicions: Namely, that large-scale corn production has changed the weather.

Over the past 70 years, farmers in America’s midwestern Corn Belt have made vast leaps in production. From 1950 to 2010, annual harvests increased by more than 400%, jumping from 2 billion to 10 billion bushels. In addition to making the area the world’s most productive agricultural region, climate scientists at MIT say the boom has created its own weather patterns.

Data from the past 30 years has found that the intensification of corn production has increased average summer rainfalls by about 35% and decreased average summer temperatures by as much as 1° Celsius.

What makes these findings so fascinating is that, while global temperatures have risen, areas like eastern Nebraska have actually cooled. Scientists believe that it’s likely that heavy agriculture counteracted rising summer temperatures that might have otherwise resulted from increasing greenhouse gases.

By comparing observed historical trends in the Corn Belt’s climate to those predicted by a variety of global simulations used by the World Climate Research Program (WCRP), which coordinates climate research sponsored by various international organizations, the report showed the models were inaccurate for the region (they predicted summer temperatures would raise and rainfall would increase by just 4%). Though the WCRP models accounted for greenhouse gas emissions and other human and natural factors, they did not consider agricultural intensification.

More corn means more transpiration which, in turn, produces slightly cooler temperatures and increased precipitation. The fact that current corn varietals (as opposed to native maize) are non-native boosts the effect.

  Corn Sweat — Large-scale Corn Production

On one hand, it has to do with what farmers refer to as corn sweat. This happens when photosynthesis boosts the amount of water vapor in the air. When a plant’s pores, called stomata, open to allow carbon dioxide to enter, they simultaneously allow water to escape. Known as transpiration, the process cools the plant and surrounding air, and increases the amount of water going into the atmosphere and returning as rainfall.

Corn sweat graphic

  Native Versus Non-Native Species

Corn is the predominant vegetation in the mid-west. Farmers have replaced the area’s vast seas of grass with millions acres of corn, which transpires at a rate 20% higher than indigenous grasses. Agriculture is literally funneling moisture into the atmosphere, and all that humidity has created a kind of protective bubble against rising temperatures.

  Increases In Corn Production

Growing more corn — and thus, creating more transpiration — would have been impossible without advances in farming efficiency. The introduction of high-yielding varieties, better irrigation, and soil management techniques, along with the ability to use computer sensors to closely monitor field conditions, have all contributed to soaring yields.

One of the biggest factors is the widespread use of cover crops, crop residue management, and no-till farming methods.

Together, the practices have erased the need for conventional tillage, dramatically increased organic matter in the soil, reduced evaporation and runoff, and lowered summer surface temperatures. With time, the native clay-based soil has become much healthier and better at retaining water. This has made crops more resilient to traumatic weather events and, in general, much more productive.

Further Reading on Climate Change:

 Climate Change Impacts On Wisconsin
 Climate Change Impacts On The Great Lakes
 Climate Change Impacts On Bees and Food Production
 Lake Michigan Warming: Climate Threats
 How Climate Change Affects Wisconsin Winters
 How Climate Change Affects Butterflies

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