Climate Change Is Coming for Your Pumpkin Pie

Unusual weather conditions could cause an entire national crop to fail.
Photographer: Frank Bienewald/Getty Images

Climate change is a threat to many things: polar icecaps, coastal property, coral atolls. But canned pumpkin?

It's not as unlikely as it may sound. About four-fifths of America's canned pumpkin comes from one small town in central Illinois. Morton, where Nestle SA operates its Libby's cannery, takes in millions of gourds from the surrounding fields in the months leading up to Thanksgiving to make the paste that many cooks believe results in the best pumpkin pie.

Chart of US pumpkin output

Such monocultures have some distinct advantages. Pumpkins are a Goldilocks vegetable, needing moist (but not sodden) soil and frost-free conditions. Those in Morton are close to perfect. In 2016, an acre of Illinois land could produce about 41,000 pounds (19 metric tons) of pumpkin, more than twice as much as most other major producing states, according to the U.S. Department of Agriculture.

Vegetables travel much better once processed and canned, so putting a factory in the middle of that pumpkin belt is by far the best way of ensuring kitchens across the country can get their supply of mashed starch.

There's a problem with this model, though: If unusual weather conditions cause yields to decline in Morton alone, the entire national crop of canned pumpkin can fail. Too much rain in the spring planting season means seeds don't get sown. Too little in the growing season, and they fail to thrive. Too much come the harvest, and tractors get bogged down while gourds are left to rot in the fields. As Thanksgiving cooks may remember, the wet autumns of 2009 and 2015 resulted in such shortages that at one point cans of Libby's pumpkin were selling for $30 on eBay.

Climate change is likely to exacerbate this trend, as Nestle itself has warned. Central Illinois already gets about two inches more early spring rainfall than it did a century ago when the Libby's factory was built, and that shift to wetter conditions with more intense downpours will probably be exacerbated over the coming decades. Average crop yields in the state will fall by 15 percent by the 2020 to 2040 period, and by 73 percent by 2100, according to a 2015 paper led by Kathy Baylis, an economics professor at the University of Illinois. It's notable in the chart above that, barring the bumper years of 2014 and 2016, Illinois pumpkin yields have been declining for a decade.

Pie is the least of the worries in this process. Illinois is the biggest producer of soybeans in the U.S. and the second-biggest of corn, and the wider midwestern breadbasket plays a crucial role in food supply worldwide. More than a third of each crop globally is grown in the U.S., according to Department of Agriculture data. North America's agricultural land is gradually shifting north and east, and will continue to do so as the planet warms.

Farmers have always managed to adapt to weather impacts, and will no doubt continue to do so as the earth heats up by improving drainage systems, spending more on insurance, and shifting their crop mix and land holdings. After the 2015 episode, Libby's planted more seeds on additional acres to limit the risk that a few farms could devastate the entire crop.

This isn't a painless process, however. All those adaptation activities ultimately raise the cost of generating a given yield from an acre of land. Growth in agricultural productivity has been central to humanity's ability to feed 7.6 billion people from the same stock of land that supported just a fifth of that population a century ago. Climate change makes that process harder, and less predictable. As we give thanks for this year's good harvest, we should pause to spare a thought for what a warmer future may hold.

This column does not necessarily reflect the opinion of Bloomberg LP and its owners.
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