Report says Iowa corn yield growth will slow because of climate change
A new report projects that climate change will limit corn yield growth throughout Iowa over the next decade and beyond.
The Environmental Defense Fund report assembled 20 different climate models to look at the impacts of climate change on yields of corn in Iowa, soybeans in Minnesota and winter wheat in Kansas by 2030 and 2050. The nonprofit environmental advocacy group zoomed in on more localized data, allowing farmers to see what the percentage change of yields in their county could look like with climate change.
The EDF found that by 2030 and 2050, Iowa, the nation’s top corn producer, will see a boost in the number of days that have a temperature good enough for corn to grow, but days of extreme heat that stress corn growth will jump more, and inhibit that growth. By 2030, corn yields in Iowa will be 5 to 25 percent lower than where they would be without climate change. By 2050, corn yields across the state will be at least 10 percent lower than where they would be without climate change.
“Here we are in Iowa, one of the most productive, best-resourced crop-growing regions in the world,” said Eileen McLellan, a lead senior scientist with the Environmental Defense Fund. “If we're going to have that level of climate impact here, imagine what that means for global food security.”
McLellan said that means the U.S. won’t be able to meet food production goals for 2050 unless farmers adapt to climate change.
The report shows Iowa corn yields increasing since 1980 and it projects a continued increase through 2060, but climate change will limit the growth of those yields.
“ … if not for climate change offsetting other productivity gains, yield per acre would be 30 bushels higher in 2030 and 60 bushels higher in 2050,” the report says.
Gene Takle, an emeritus professor of agronomy at Iowa State University, had been asked to review the report a couple of years ago and has scanned the published report. He said the report uses “well established” methods.
Iowa has had few heatwaves in the past 30 years compared to other parts of the country and the world, Takle said.
“The takeaway is, yes, there's going to be some yield declines from the trendline,” Takle said, “but because we're starting at a more favorable condition, it's not going to be as critical as it might be in some other parts of the world.”
But climate change, Takle said, doesn’t just bring extreme heat events. There’s also a link between climate change and heavier rainfall, which isn’t addressed in the report’s section on Iowa. Takle said the report’s county-by-county results need to be “interpreted cautiously” because there tends to be a lot more county-by-county variation with precipitation.
The report lays out different modifications farmers can make to their farms to adapt to climate change, such as gene-editing crops, farming practices that benefit soil health, and improving crop diversity.
McLellan, the EDF’s lead senior scientist, said some of these changes will take time to implement.
“There's no question that things are going to get much, much, much worse by 2050,” said McLellan, adding larger scale changes may be needed by 2040.
Bruno Basso, a crop modeling and land use sustainability professor at Michigan State University, said he hadn’t read the report, but he attended a symposium hosted by the Des Moines-based World Food Prize Foundation where it was unveiled. Basso said he wasn’t surprised by the findings.
“Adaptation is just key,” Basso said. “Adaptation will also allow us to reduce the [greenhouse gas] emissions coming from agriculture so we’ll lower the impact of climate change, and we need to do that.”
Many farmers have already made some of those changes. Iowa row crop farmer Larry Buss has not tilled his soil since 1985, which means he doesn’t disturb his soil to plant new crops. No-till farming helps keep carbon in the soil, rather than releasing it into the atmosphere as the greenhouse gas carbon dioxide.
“All this comes down to that we have increased soil productivity where we get more yields for proportionally less inputs than we did historically,” Buss said.
Buss said many Iowa farmers already do the practices listed in the report because it “makes good economic sense.”
“Iowa farmers take production seriously, they take the environment seriously, they take their soils seriously,” Buss said. “ … going forward with climate change, I’m sure we will adapt.”