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As increasing heat makes fire seasons longer and more intense, a team of scientists is looking to this U.S. state to see what might happen to potato yields – and their findings could have huge implications for North America’s food supply

On a sunny September morning, harvested potatoes pile up in a truck at Gross Seed Co. in Greenleaf, Idaho. Farmer Doug Gross says his yields are lower this year after a hot summer. Nathan VanderKlippe/The Globe and Mail

It was in 2012 that Addie Waxman started to notice a problem in the potato fields that keep North America’s burger joints and grocery freezers stocked with French fries. She was in Washington state, walking through smoke so thick she could barely see, and noticed that some of the potato plants looked as if they were shrivelling earlier than expected.

It seemed some plants were vulnerable to the dense haze blanketing the field. When plants wilt, they can no longer convert sunlight into sugar – and sugar into starch. “So if the vines go down early, then they’re not making enough potatoes, or large enough potatoes,” said Dr. Waxman, who holds a PhD in potato science. And if the potatoes are stressed, they could also perform more poorly in storage.

Could the smoke be to blame? “I was like, whoa, I think that’s something we ought to know more about,” she said.

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Mr. Gross holds some of his produce.Nathan VanderKlippe/The Globe and Mail

A decade later, Dr. Waxman, now the manager of agronomy for McCain Foods, is watching carefully as a group of scientists work to answer that question in Idaho, a state that is the company’s largest-growing region and home to its largest processing plant in North America.

The research group is midway through a two-year study designed to tease out how smoke affects everything from the size of a potato tuber to its chemical composition, from its durability in storage to the colour of the French fries it yields.

The results could have important implications not just for McCain, the Canadian-headquartered food giant, but also for the vast agricultural industry in the western parts of the continent – and the fast-food appetites of a continent. Roughly half of all Idaho potatoes are made into French fries.

Climate change, and the advent of warmer summers and fiercer wildfires, has made the research more pressing. The past two summers in Idaho – No. 1 in the United States for potato production – have been the hottest in the state’s history. This year, Boise highs exceeded 38 C a total of 27 times, seven more than the previous record. And, as in much of western North America, smoke from forest and grassland fires is darkening summer skies with increasing regularity. Potato growers say yields are down by 10 to 15 per cent.

What makes smoke particularly worrisome is that it can affect large geographic areas, filling entire valleys.

“We’ve had years where basically the whole month of August is smoky,” said Mike Larsen, chief marketing officer for the Mart Group, a large Idaho potato producer.

“The smokier the skies are, the less light that gets down here – and the less photosynthesis that is going to happen. It is going to have a yield impact. It’s just, how much?”

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Idaho is the highest-producing state for U.S. potatoes, thanks to farmers like Mr. Gross. Like the rest of western North America, it’s also seen increasingly intense wildfires and smoke coverage in recent years.Nathan Vanderklippe/The Globe and Mail

The Cedar Creek fire in Oregon, one of Idaho’s neighbour states, as seen from a satellite on Sept. 9 and from the ground on Sept. 13. Planet Labs PBC, Oregon State Fire Marshal/AFP via Getty Images

That’s what researchers are trying to determine. This spring, the Idaho team planted three varieties of potato. For six weeks beginning in July, they covered the plants each morning from 5 a.m. to 9 a.m. with plastic sheeting, then set fire to a cocktail of hardwoods, mesquite pellets and pine needles. They piped the resulting smoke in to several of the rows, leaving others unsmoked to provide a point of comparison. The aim was to replicate the composition and density of wildfire smoke, which contains ozone, brown and black carbon, and volatile organic compounds.

Mornings are when the plants’ breathing pores begin to open. If the potatoes are “going to take those compounds into the leaf, it would be in that time frame,” said Mike Thornton, a plant scientist at the University of Idaho with deep family ties to potato research.

Changes to a potato’s makeup can affect the quality of a French fry. Too much sugar and it will turn dark, as if it was caramelizing. Too little starch – what the industry refers to as solids – and the fry can go hollow when cooked. If a potato is too small, the fry will be too short to make its seductive peek out of the top of the McDonald’s box.

But wildfire smoke has become a growing concern across the agricultural industry.

A British-Chinese study in 2018 documented reduced photosynthesis from higher ozone levels caused by large burns and concluded that fire pollution “poses an increasing threat to ecosystem productivity in a warming future world.”

Last year, another Idaho study found that a dairy cow’s milk production could drop by as much as five litres a day – roughly 10 per cent – during periods of heavy wildfire smoke.

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Wildfire smoke obscures the setting sun over a vineyard in Finley, Calif., in 2018.Marcio Jose Sanchez/The Associated Press

Vintners, too, have come to fear smoke taint in grapes. It can produce flavours in wine described in academic literature as “ashy” and “burning rubber.” Sophisticated scientific tools, including spectroscopic techniques and machine learning, have been employed to better understand what is happening, including the ways compounds from smoke are altered by fermentation.

“Everybody is trying to figure out what to do,” said Greg Jones, a climatologist who is chief executive of Abacela Vineyards and Winery in Roseburg, Ore. Like grapes, many potatoes are grown in climates that are naturally dry in summer, and becoming even more so with climate change. In Canada, for example, 40 per cent of potatoes are grown in Alberta and Manitoba.

Mr. Jones’s research has pointed to another way smoke can upend agriculture. In 2020 he monitored temperatures in rural areas affected by smoke and compared those with unaffected places. The differences were stark: Beneath smoke, daytime temperatures were 4.5 to eight degrees cooler. At night, temperatures remained three to 4.5 degrees warmer.

For potatoes, warmer nights can wreak havoc. Instead of consolidating starches in the evening cool, the plants spend the night perspiring, burning off any gains they have made. Smoke also tends to trap humidity, keeping dew on plants, which can speed the spread of pathogens such as early blight.

“What has hurt us more than anything is the hot nights,” said Doug Gross, a respected potato farmer who grows about 20,500 metric tonnes of potatoes a year just west of Boise and is now on his 48th crop.

After the intense heat of this summer, Mr. Gross said, yields are down 10 to 15 per cent.

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Mr. Gross says hot nights are the main reason his yields were lower this year.Nathan Vanderklippe/The Globe and Mail

Farmers and researchers hope the smoke study can help identify whether certain varieties are less vulnerable. It may also drive genetics research. “I would expect that in the future, potatoes could be bred that are more smoke tolerant,” said Joseph Guenthner, an agricultural economist who is an emeritus scholar at the University of Idaho.

Advanced manufacturing technology could also help transform smoke-exposed potatoes into higher-grade products, said Owen McDougal, a food chemist at Boise State University.

Both men are working on the smoke research project – and what they and the other scientist learn could have bearing on other crops as well.

In Idaho, farmers have already begun asking Prof. Thornton, “If you get this figured out for potatoes, can you do it for onions?”

On Mr. Gross’s potato farm, the harvest continues. Nathan VanderKlippe/The Globe and Mail

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