Thanks to global warming, North American wheat production is set to move back in time.
Temperatures in the nation's bread basket could rise by 4 degrees or more over the next century, according to U.N. projections, forcing American farmers to change how they go about growing more than 2 billion bushels of wheat each year. It is a stark shift -- but one that has happened before, according to a study published late last month in the Proceedings of the National Academy of Sciences.
"None of this is completely new," said Paul Rhode, an economist at the University of Michigan and one of the study's authors. Wheat shifted once before, into colder regions, the opposite direction of what is expected under climate change, he said. "Meeting these challenges is an ongoing, long-standing process."
Until the late 1800s, U.S. wheat production was centered in states like Ohio and New York, balmy regions when compared to South Dakota, wheat's current locus. But due to a variety of factors -- population growth, cheap land, aggressive marketing by the railroads -- farmers pushed their wheat fields up into cold, dry climates. Through trial and spectacular failure, these pioneers used breeding and biological exploration to shape the crop well before the rediscovery of genetics.
"Wheat production moved a very long ways into much harsher environments," said Alan Olmstead, an economist at the University of California, Davis, and Rhode's longtime publishing partner. "Farmers moving into these areas failed year after year, until they figured it out."
Extracting historical production data available since 1839, Olmstead and Rhode built a decade-by-decade map of wheat's move from the Ohio River Valley to the Great Plains and Canada, a shift that was largely completed before the Great Depression. Over the past 170 years, they found, the average temperature for wheat production fell by some 4 degrees Celsius, and the crop currently grows in regions that receive half the average rainfall than historical Eastern states.
Comparing this historical shift to future scenarios, Olmstead and Rhode conclude that while the wheat frontier is likely to move northward into Canada and Alaska, this movement, they write, "is unlikely to be as great as the past geographic shifts in production." The expanded tolerance of wheat, they add, can be seen in its simultaneous growth in northern Mexico and Canada, demonstrating that "the historical record of adapting wheat cultivation to areas with widely varying climates is impressive."
This past success, however, is not an argument to postpone action lowering greenhouse gas emissions, Rhode said. Rather, the study is an example of the historically informed work that will be needed to inform adaptation to warming temperatures that will come even with drastic action to halt global warming.
"Looking at the historical record for sound adaptation is critical," he said.
The study was prompted in part by past exaggerations. Building off and distorting climate projections released by the International Maize and Wheat Improvement Center, the BBC published a "dire map" showing the U.S. wheat belt surging northward, Rhode said. However, many of the regions highlighted as wheat producing in the map "had dropped out a century ago," he said.
There are many causes that contributed to wheat's migration, and their relative importance remains controversial. There was population growth in the East and massive tracts of cheap, unproductive land in the Great Plains. The railroads recruited settlers to the region, including immigrants, like Russian Mennonites, known for their ability to grow wheat in the cold. ("Seed came with settlers," the saying goes.) And super-productive corn, along with cattle and swine, began to muscle into wheat's turf.
These farmers found themselves in what was known as the "Great American Desert," land thought incapable of supporting agriculture. And at first, it was. Traditional wheat varieties perished, even as increased mechanization began to cut down on the labor needed to harvest the crop. Only when hardy wheat varieties -- known by names like "Red Fife" and "Turkey" -- were imported from the harsh plains of Eastern Europe did wheat begin to thrive.
The Canadian and U.S. governments both supported research into adapting wheat. Around 1900, a legendary plant explorer working for the Agriculture Department, Mark Alfred Carleton, introduced multiple wheat varieties he had secured from the Russian Empire. And a crossbred variety developed by the Canadian government in the early 1900s, called "Marquis," came to supply nearly all the country's farmers.
Since its geographic shift, plant scientists have continued to improve wheat, of course, including the growth of high-yielding hybrid crops developed in the Green Revolution. (Given their large export market, wheat farmers have remained wary of genetic engineering.) Adapting to warmer temperatures, then, won't be a simple matter of resurrecting old seed and will require innovative breeding and research.
But while it will be a change, at least for the next century, it will not be unprecedented, Rhode said.
"It's a change," he said, "within the frame of past changes."