If Climate changes that are predicted as a result of global warming turn out to be true, the U.S. Corn Belt will be one of the winners in a world where many agricultural regions will decline. But climate change will still present challenges for Corn Belt farmers, even though the region as a whole will retain its advantaged position for producing corn and soybeans.

“The Corn Belt, no matter what climate scenario you choose, will continue to be the best place in the U.S. to grow corn and soybeans,” says Otto Doering, a Purdue University agricultural economist who has studied the potential impact on agriculture of climate change predicted by major computer models.

Climate change induced by global warming won't be uniform across the Midwest, the United States, or the world, says William Easterling, director of the Penn State Institutes of the Environment and formerly with the University of Nebraska. “Greenhouse warming is not likely to be the same in pace and magnitude everywhere,” he says.

Within the Corn Belt, the climate change models suggest that there will be regional differences that will reduce productivity in some areas. Other regions within the Corn Belt will benefit from changes that will make farming more productive and potentially more profitable — at least for a time.

The winner is …

The Northern Corn Belt is a clear winner under major climate change scenarios that play out through the middle of the century. As the climate warms, this region will be able to successfully support the growing of longer-season corn hybrids and soybean varieties. In general, precipitation will be adequate to allow these more productive cultivars to produce higher yields compared with crops grown in this region today.

Meanwhile, in the Central and Southern Corn Belt, corn could suffer as higher temperatures make the climate less hospitable to corn, despite an expected increase in annual precipitation. Soybeans and winter wheat could be a bright spot here, however.

The Western Corn Belt is a wild card. Some models suggest that dryland farming could be the beneficiary of more annual precipitation, which would help crops cope with expected higher temperatures. But Steve Hu, a climatologist at the University of Nebraska-Lincoln, says that other models suggest dryer conditions, which could make dryland crop production more challenging.

Regardless of the region, the future laid out by climate change models will place a premium on adaptability. To be successful, farmers will have to alter management practices to compensate for weather that is likely to be hotter, wetter and more variable, with longer periods between rains.

Global warming basics

The popular image of global warming is of a drought-stricken, heat-laden future. But major climate change models paint a more nuanced picture of higher temperatures and higher moisture for much of the Midwest through the middle of the century. After that, crystal balls get cloudier and the outlook bleaker.

Here's a quick take on what is likely to happen, based on major climate change models: As levels of carbon dioxide (CO²) and other greenhouse gases rise, the earth holds more heat. This causes more moisture to evaporate, inducing more precipitation. This additional moisture may be enough to allow crops to compensate for higher temperatures, at least for several decades, in many areas.

“What goes up has to come down,” Easterling says. “Across the entire earth, precipitation will have to increase.”

The catch is that at some point, when average temperature rises about 5°F, “you begin to rev up plant evapotranspiration and you actually start to dry out,” Easterling says. This could begin occurring in the middle to the later part of the century.

Signs of change

Weather patterns in recent decades suggest climate change already is under way, says Gene Takle, an Iowa State University climatologist with the Regional Climate Modeling Laboratory.

The increasing length of the growing season is clear evidence. “Over the past 50 years, the number of frost-free days in central Iowa has increased by eight or nine days,” he notes.

In Nebraska and other parts of the Plains, the heading/flowering date of winter wheat, which is dependent on cumulative heat units during the growing season, has moved up a full two weeks over the past 70 years, notes Hu, the Nebraska climatologist.

Temperature records corroborate a general warming trend, Takle says. In recent decades, across much of the Midwest, average nighttime temperatures have gone up, both in winter and summer. Winter daytime temperatures are up as well.

However, summer daytime temperatures have actually fallen in parts of the Midwest, possibly due to trends toward higher precipitation, which cools the atmosphere as it evaporates, Takle says.

“Observations show that in the center of the Midwest [centered on the western edge of the Corn Belt], daytime maximum temperatures have gone down 2°F in the past 20 years,” he notes.

“If you think about what it is like the day after a rain, it is muggy and the temperature doesn't go up as fast because the heat is being used to evaporate moisture,” Takle explains. “That is part of the reason we are seeing the cooling of daytime maximum temperatures.”

Increasing cloud cover in the Midwest could be another related factor, says Michelle Wander, a University of Illinois soil fertility specialist who studies climate trends. “Because of increasing average summer temperatures, we have more evaporation, so we are cloudier, which helps hold down temperatures. We are already in this humidified experience. We would be in a worse position if this weren't occurring.”

Both Takle and Wander note that, while precipitation is likely to increase with climate change, rainfall is likely to be more infrequent and more likely to come in large amounts when it does fall. That could mean more potential for soil erosion, drought stress between rains, and planting and harvest difficulties, if excessive rain occurs at these critical times.

Regional details

A book titled Effects of Climate Change and Variability on Agricultural Production Systems, edited by Doering, the Purdue University ag economist, and several others, takes a detailed look at the implications of global warming on crop production systems across the Central Corn Belt through about 2060. The researchers conclude that corn, soybeans and winter wheat will continue to be the major crops grown in the Central Corn Belt. They expect farmers to manipulate crop maturities, planting dates and the relative proportion of the crops in rotations, among other factors, with changes in the growing environment. States included in the study were Illinois, Indiana, Ohio, Michigan and Wisconsin.

The researchers used two climate change models to evaluate the potential effects of environmental changes. Projected yields, among other factors, varied depending on the model used and the specific cropping area within regions. For simplicity, projected yield changes from only one of the models are reported here. The book did not make projections for the Western Corn Belt, so none are included here for that region.

Northern Corn Belt changes

The climate change model predicts that corn yields from full-season hybrids will increase up to 45% compared with current yields in parts of the Northern Corn Belt. In other parts of the region, corn yields will remain relatively flat compared with today's yields. These yield projections are based on productivity of current hybrids and do not include potential gains from genetic improvements.

The study projects soybean yields from full-season varieties to climb 20 to 50%. Winter wheat yields will almost double, although they will still be lower than yields farther south in the Corn Belt. The crop is projected to continue to be a minor player in rotations.

An economic analysis of the impact of these productivity changes reported in the study shows that a corn/soybean rotation will continue to dominate in most parts of the region, although soybeans could play a stronger role than is currently the case. Overall, economic returns could go up $50 to $100/acre compared to today's returns because of higher productivity.

Midsection Corn Belt changes

The model predicts that corn yields from full-season hybrids will hold their own at best and could conceivably fall as much as 45% compared to current yields in parts of the midsection of the Corn Belt (central Illinois and central Indiana). It projects soybean yields from full-season varieties to climb 10 to 50% and winter wheat yields to go up 50 to 100%.

An economic analysis of changing productivity of these crops shows that, despite higher winter wheat yields, a corn/soybean rotation could crowd out the limited winter wheat now grown in the region. Average returns could hold at today's levels, or be up slightly.

Southern Corn Belt changes

The study predicts that corn yields from full-season hybrids could fall as much as 30% compared with current yields across much of the region as daily maximum temperatures begin to resemble those of states to the south, where corn is less productive. Soybean yields from full-season varieties could climb 10 to 30% across much of the region. Winter wheat yields could be up 10 to 20%.

An economic analysis of the impact of changing productivity of the three crops shows that a corn/soybean rotation could nearly crowd out the winter wheat now grown in the region. At best, average returns are projected to hold at today's levels or could fall about $30/acre compared with today's returns.

Behind the yield changes

Varying productivity changes of the three major crops are partly the result of the crops' ability to benefit from — or withstand — higher temperatures and rainfall, according to the Doering book. Higher CO² levels are another factor. Soybeans and wheat, and to a lesser extent corn, could benefit from higher levels of the greenhouse gas. Although the impact of CO2 “fertilization” is a matter of debate in the scientific community, for the purposes of the study, the researchers assumed that soybean and wheat yields could increase up to 30% because of higher CO2 levels, while corn yields could go up 5%.

Doering and other researchers warn that there are plenty of wild cards that could disrupt these global warming scenarios, not the least of which is the imprecision of projection models themselves. Agronomic factors could include increased disease and insect pressure as a result of warmer temperatures, which could also hamper yields.

The climate scenarios used in the Doering book may be too mild, adds Wander of the University of Illinois. In the years since the book was published in 2002, many studies suggest that shifts in patterns and intensity of rainfall and challenges from pests, ozone and other factors are likely to result in growing conditions that are more challenging than previously thought.

“In general, I think the directions suggested in the book are correct, but problems suggested for the southern part of the region, including losses in potential productivity and increased yield instability, are likely to be experienced more widely,” Wander says. “There already is research showing mid-season water stress frequently reduces yields in central Illinois, where we farm some of the region's best soils.”

Given the changes already being seen in rainfall distribution, including more intense spring and fall events, Wander stresses the importance of soil protection and water management. “In order for farmers to cope with this effectively, they need to implement soil-conserving practices now and not in 30 or 50 years,” she says.

Planning ahead

Climatologists acknowledge that climate models used to project the impact of global warming on climate change are rife with assumptions that can't be proved — or disproved for that matter. So does it make any sense to pay attention to these projections?

“We can't trust the models for specifics, but the trends can help identify possible futures,” says climatologist Hu. “Models are helpful for strategic planning to help plant breeders and others to prepare for possible changes. We should be prepared for the worst scenarios.”

On the farm level, being aware of the potential effects of global warming can keep producers alert to strategies that help them adapt to the changing environment, Doering says. “As things begin to change, farmers can begin to play with the date of planting and maturities to move the sensitive times for the plant to a different time period,” he says.

“You don't have to be a converted climate-change fanatic” to learn from this sometimes controversial discussion,” Doering adds. “Our feeling is that these projections aren't necessarily about predicting disaster, but about providing a framework for assessing risk in the future.”