For years, the literature on climate change and agriculture has forecast a bleak future. Climate scientists warn that a warming world will bring a host of challenges for farming: increased humidity that spreads crop disease, more frequent heavy rainfall inundating fields, and warm winters that lure pests. This could have a devastating effect on food sources like corn and soybeans in the American Midwest.
Most researchers on this issue have focused on rising temperatures. A commonly cited 2009 study estimated that even the slowest warming scenario could decrease crop yields by nearly 50 percent; others have halved this prediction, but the outlook remains dire. Last month, NPR published a story lamenting the end of many key American crops—almonds, peaches, and corn among them.
None of this even gets at climate change's more dramatic effects: hurricanes that pick cotton fields clean, or floods that devastate a once-in-a-lifetime crop. As Pacific Standard reported after Hurricane Michael, farmers in Georgia say the latest round of storms may be the tipping point. They'll have to adapt to survive, changing planting schedules, crop varieties, or moving away from monoculture.
A new study shows that some farmers have already done this successfully. Ethan Butler, now a postdoctoral associate at the University of Minnesota, conducted a historical analysis of corn yields in the 20th century in one of the first attempts to evaluate the effects of climate change on crop yield, while also taking farmers' adjustments into account. His findings suggest that corn in the Midwest has actually benefited from warm, but still moderate, daily temperatures. (If the growing season were any hotter, Butler says, this would not be the case.)
Recent projections have anticipated "alarming scenarios," the authors write, but "the presumption of no adaptation seems at odds with the ingenuity of farmers." Butler's models show that previous warming has increased the number of days suitable to growing corn. In response, yields have improved—but only because farmers also changed their planting schedules and selected varieties that develop better in a longer growing season.
"The combined changes that farmers, crop breeders, and agronomists have realized for [United States] maize production have better aligned the timing of crop growth with historical seasonal conditions," the study says. Climate, as much as technical improvements in agriculture, played a role in this success.
It's important to note that these farmers were not adapting to "negative" climate change, but to more favorable conditions, Butler says. To further this trend, they would need to continue to adapt. The researchers also warn that droughts in two outlier years—1988 and 2012—devastated crop yields; as droughts become more frequent and severe, as NASA scientists predict, these outliers could become the norm. Under more extreme warming, the shift to a longer growing season would actually backfire.
Still, Butler says that his findings suggest farmers have adjusted to changes in climate before—a factor that's not always present in big-picture projections of U.S. agricultural output. "It shows some agency on the farmers' part," he says. "They aren't just mutely being affected by climate-responsive agriculture."
In practice, Butler hopes the union of climate and crop-production research will result in more accurate forecasts, helping farmers better prepare and adjust. For now, he's satisfied to be engaging farmers in this work, especially because studies have found that Midwest farmers are among some of anthropogenic climate change's strongest skeptics.
"I think it's a lot easier to dismiss research about climate change when it ignores what the people who are going to be affected are actually doing right," he says.