Climate change figures to make Iowa hotter, wetter

Photo courtesy of Iowa Department of Transportation

This photo shows a road destroyed by flooding during the 2008 flood of the Cedar River near Atalissa in Muscatine County. Climate change figures to increase spring precipitation, leading to more floods.
Photo courtesy of Iowa Department of Transportation This photo shows a road destroyed by flooding during the 2008 flood of the Cedar River near Atalissa in Muscatine County. Climate change figures to increase spring precipitation, leading to more floods.

Iowa’s climate is expected to be hotter and wetter in the coming decades.

That seems to be the consensus of climate scientists and agronomists, who say that the changing climate will affect agricultural production in the state. Though areas north of Iowa such as Minnesota, the Dakotas and Canada have the most to benefit from warmer temperatures, the climate scientists the Union interviewed said Iowa will probably be harmed overall by climate change.

Effect on crops

Dennis Todey, director of the Midwest Climate Hub in Ames, said the long-range forecast for climate change in Iowa is that it will make agricultural production more difficult. However, the warmer temperatures will allow Iowa’s northern neighbors to grow crops they couldn’t before. Todey said warming temperatures have made corn and soybeans more viable in North and South Dakota, parts of Minnesota and Canada.

“We’ve seen an increased amount of precipitation in the Dakotas. Corn plants need 22-24 inches of water a year to grow, and previously, [the Dakotas] did not receive that much, but now they are,” Todey said.

Iowa State University Extension and Outreach field agronomist Virgil Schmitt said the Dakotas and parts of Canada that once relied on small grains such as wheat, barley, triticale and sunflowers are now switching to the more lucrative crop of corn.

“Climate change is moving the cornbelt north and west,” he said.

For Iowa’s soybeans, however, the extra rainfall climate change has brought is not good for crop, which Schmitt said, “don’t like wet feet.”

Unlike its northerly neighbors, Iowa is unlikely to switch to growing a different crop because of climate change, he added.

“We don’t have a good financial alternative to soybeans and corn,” he said. “We desperately need a third and fourth crop. Hay might be one, but you can’t make as much money selling it.”

Schmitt predicts that seed companies will respond to climate change by producing beans that can better tolerate wet soils, and to produce corn that can better tolerate weather extremes in general. He said improvements in genetics have allowed crops to produce well even in bad weather. For instance, the state experienced a drought last year, and yet still posted good yields.

“If we would have planted seeds with 1960s-1980s era genetics, last year would have been a disaster,” Schmitt said. “Plant breeders have made crops that can tolerate stress and still be extremely productive.”

Todey said his lab’s climate models show corn and beans becoming more difficult to grow in southeast Iowa as the 21st century progresses. If new seed varieties cannot keep pace with the changing climate, he foresees more land reverting to grassland or pasture.

More rain and yet more droughts

One of the major effects of climate change that scientists predict is an increase in droughts. This may seem counterintuitive given that climate change has also produced more precipitation. How can it cause more rain and more droughts at the same time? Justin Glisan, the state climatologist for the Iowa Department of Agriculture and Land Stewardship, said it all has to do with when the rain falls.

Gilsan said the trend is for climate change to increase Iowa’s precipitation in all seasons except summer, when crops need it the most.

“What we have seen across Iowa is a seasonal shift in precipitation,” he said. “We’re seeing rain/snow events earlier in spring, and also increasing in fall. In between, we are seeing a decrease in rainfall in the summer months, particularly in early July through August.”

Gilsan said these conditions can exacerbate already dry conditions during the hottest time of the year when a crop is maturing and relying on subsoil moisture.

Gilsan said there are things farmers can do to prepare for drier summers and more rain in the spring and fall. He recommends planting cover crops to reduce soil and nitrate loss from heavy rains, and mentioned that cover crops have the added benefit of absorbing carbon from the atmosphere.

The Environmental Protection Agency published a report in August 2016 titled “What Climate Change Means for Iowa.” In it, the EPA describes how climate change has been caused by an increase in carbon dioxide in the atmosphere, 40 percent more today than in the late 1700s.

“These gases have warmed the surface and lower atmosphere of our planet about one degree during the last 50 years,” the EPA wrote.


Additional rainfall, especially in the spring, figures to make flooding more common and more severe. Todey said this past spring’s devastating floods, particularly the one on the Missouri River in western Iowa, were caused by rain falling on frozen soil. Since it couldn’t soak into the soil, the rain filled the river so much it covered Interstate 29.

In September 2019, the Iowa Policy Project published research on the effects of climate change on Iowa. The report was by James Boulter, a professor of chemistry in the Watershed Institute for Collaborative Environmental Studies at the University of Wisconsin-Eau Claire, and supported by a grant from the Environmental Defense Fund.

Boulter’s report, “An Uncertain Future,” addresses the massive flooding the state suffered earlier this year on both the Missouri and Mississippi rivers, and how climate change plays a role in the frequency and severity of floods. In the east, the Mississippi River reached a flood-stage for 38 days, resulting in a levee breach in Davenport. Meanwhile in the west, the “Missouri River basin took on more runoff in three months than it typically gets in a year,” Boulter wrote. The Army Corps of Engineers reported 47 levee breaches on the Missouri River during the spring and summer of 2019, with every levee in Iowa south of Council Bluffs affected.

Boulter noted that some of the Midwest’s wettest years on record have occurred in just the past two years. For instance, Iowa received more than 50 inches of rain from May 2018 to April 2019, breaking the old record established in 1902-03 by 2.5 inches.

Is greater carbon dioxide in atmosphere good for plants?

Plants absorb carbon dioxide and release oxygen, the reverse of animals that breathe oxygen and release carbon dioxide. With that in mind, could more carbon dioxide in the atmosphere help plants grow? Yes, this appears to be true, but it affects some plants more than others. For instance, Todey said that soybeans might benefit from elevated carbon dioxide levels, but that weeds will benefit from it even more. In particular, a weed originating in Japan and now prevalent in the southern United States is a milk thistle called kudzu, which Todey said “likes carbon dioxide a lot.”

Shorter winters, longer growing season

Todey predicts insects will be a bigger problem in the future because more of them will be able to survive the warmer winter.

“One of the benefits in our area is that cold winters kill off insects because they can’t overwinter,” he said. “Those longer growing seasons, which are good for crops, are also better for insects. Insects might get another life cycle during the year.”

Schmitt said the length of the growing season is already noticeably different from what it was a half century ago. Schmitt mentioned a study that looked at the average first and last frost of the year from 1951-2010. The study found that in the latter half of that time frame from 1981 onward, the last occurrence of a 32-degree day in the spring was six days sooner, while the first occurrence of a 32-degree day in the fall was six days later. That meant the growing season was 12 days longer between 1981-2010 than between 1951-1980.

“We’re seeing a movement toward longer maturing crops in corn and soybeans,” Schmitt said.

That same study looked at average precipitation, finding that rainfall increased a little over 10 percent from an average of 34.8 inches between 1951-1980 to 38.4 inches between 1981-2010. Unfortunately for farmers, that extra rain is coming either in the spring when they’re trying to plant, or in the fall when they’re trying to harvest.

Todey added that warm winters aren’t necessarily good for all crops. He mentioned that certain fruit trees need a certain number of hours at cool temperatures, and if they don’t get them, their fruit won’t be as good the following year.

Warm nights

Todey said now that a lot of animals are raised in confinements, the climate doesn’t affect them as much as when they’re outside. But those animals that remain outside figure to be under greater stress in the coming decades, particularly from high nighttime temperatures.

“Livestock can handle warmth during the day, but if it’s not cool at night, it’s tough on them and they don’t gain well,” he said.

Schmitt said crops react the same way to warm nights. He said if a plant can’t cool down at night, it has to use more water and more resources, and that leaves it vulnerable to the midday highs it will experience the next day. If nighttime temperatures are too high, the plant will mature prematurely and not yield as well.

In 2009, the Iowa Climate Change Impacts Committee was established to review climate change impacts and policies for Iowa. It delivered its report to the Governor on Jan. 1, 2011, in which it identified ways in which the state’s climate has changed in the past century, and how it is likely to change in the coming century.

Key findings

• More rain — The committee stated that Iowa has received steadily greater precipitation, increasing 8 percent from 1873 to 2008. It found that the increase in precipitation has been greater in eastern Iowa than in western Iowa.

• Warmer and shorter winters, and warmer nights — It found that winter temperatures have increased six times more than summer temperatures, and that since 1970, nighttime temperatures have increased more than daytime temperatures. The shorter winters are responsible for plants leafing out and flowering sooner, birds arriving earlier in the spring, and animals that prefer warm weather being seen farther north than their typical habitat.

• More storms — Iowa is a noticeably more humid state than it was four decades ago, with 13 percent more atmospheric moisture than 35 years ago as indicated by a 3-5 degree Fahrenheit rise in dew-point temperature. The committee wrote that this extra humidity in turn generates more thunderstorms and more precipitation.

• More extreme weather — One important point the committee stressed in its report is that climate extremes, not averages, have the greater impact on crop and livestock productivity. The committee foresaw that climate change would result in greater soil erosion and water runoff, more challenges for manure applications, and creating the conditions favorable to unwanted pests and pathogens.

• Public health effects — The committee indicated that the public health effects of climate change are bad. Specifically, it predicted increases in heart and lung problems from increasing air pollutants of ozone and fine particles enhanced by higher temperatures; increases in infectious diseases transmitted by insects that require a warmer climate; and greater prevalence of asthma and allergies.