Hot Beans!: How Climate Change Threatens America's Second Biggest Crop

Warming in the heartland cost soybean farmers $11 billion.

National Journal

Shawn Conley ends every email he writes the same way: "Coolbeans!" he writes where another might say "regards" or "sincerely" or just "thanks!"

Conley is an agronomist at the University of Wisconsin. He comes from a farming family. He's even written a children's book on soybean science called COOLBEAN The Soybean. Most people, he says, don't know his real first name. "They call me Coolbeans." If there ever was an ideal source to talk about soybeans, it's Conley.

Conley is concerned about the future of American soy farming. In sheer acreage, soy is the second biggest crop in the United States, the largest soybean producing country in the world. In 2014, U.S. farmers harvested around 3.97 billion bushels of soy — a record. These astronomical numbers are the result of advances in science: seeds are bred for larger harvests, farmers have better data on when they should plant. From 1960 to 2009, the average yield per acre increased from 23.5 bushels per acre to 42.3 bushels per acre.

But during the same time period, the United States has gotten warmer and warmer. Seven of the hottest 10 years on record in the U.S. have occurred since 1998. What Conley and his colleagues across the soy-producing states wanted to know was this: Could those historic soybean yields have been even higher, if not for climate change?

The short answer is yes. The results of their study, recently published in the journal Nature Plants, find that over the last 20 years, U.S. soybean growers have missed out on $11 billion due to climate change. It has been a hidden cost, cloaked behind advances in seed science.

"We've been able to have a net yield game over time, but it is not as big as it could have been," Conley says. Their report estimates — by combining yield data, weather data, and then filtering out the gains from technology advances — that for every 1 degree celsius rise in in growing season temperature, soybean yields fell 2.4 percent.

There are winners and losers. The more northern states of Wisconsin, Minnesota, and South Dakota all saw increases in their soybean production due to weather. This matches other agricultural trends. The corn belt — the ideal geographic area for growing corn — is literally moving northward, into North Dakota and Canada. "You can plant a soybean variety that 20 years ago would probably be planted 200 miles south of us," he says.

The irony is farmers, as a group, don't readily believe in climate change. A 2014 survey from Purdue University found that 66 percent of farmers surveyed believe in climate change (just 8 percent say it's human caused). The same survey found 90 percent of scientists and climatologists say climate change is real. Which makes it hard for scientists like Conley to convey the results of his studies. Even even avoids using the term climate change. But, he says, when he frames climate change as an economic problem, it's more likely to resonate.

Estimating the costs of climate change is important because these estimates can help determine how governments might intervene. Without estimates, it hard to know how to act.

"The costs of climate change are going to determine mitigation, are going to determine how much money we should be spending to reduce emissions," said Frances C. Moore, a Ph.D student at stanford who recently published a study estimating the worldwide cost of carbon in Nature Climate Change. Her study determined that the previous estimate of $37 per ton of carbon dioxide was much too low. It's closer, she believes, to $220 a ton. She said as these numbers continue to be revised, the evidence suggests they'll only increase.

"There are a lot of reasons why the social cost of carbon might be quite a lot higher than the official numbers today, and there don't seem to be a lot of reasons why it might be a lot lower," she said.

While Conley says there isn't a tipping point for U.S. soy and that yields won't come crashing down, he says the findings should be a call to adapt and innovate. "I'm not going to be a doomsayer, saying we're not going to grow soybeans," he says. "But the way we grow soybeans could be dramatically different."

Correction: This article originally mistated the average yeild per acre for soybeans.