Behind the Forecast: Climate change affecting French fries? Say it ain’t so

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Updated: Dec. 18, 2020 at 10:31 AM EST
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Potatoes were first cultivated about 10,000 years ago. Now they are cooked and devoured...
Potatoes were first cultivated about 10,000 years ago. Now they are cooked and devoured hundreds of different ways.(Pexels)

LOUISVILLE, Ky. (WAVE) - Potatoes are a staple in our diet. They can be fried, baked, mashed, smashed, made into chips or soup, and even more. Our changing climate may threaten our favorite vegetable.

Potatoes were first cultivated in South America about 10,000 years ago. They are now grown on most continents; however, most potatoes are grown in the Northern Hemisphere. Idaho and Washington produce most of the United State’s potatoes. Idaho grew more than 13 billion pounds of potatoes in 2019, according to the United States Department of Agriculture (USDA). Washington produced just over 10 billion pounds that year. Wisconsin was in third place, yielding around 2.8 billion pounds.

Typically, farmers plant potatoes in early April through late May. Their tubers (the parts we eat) begin to form in June, according to the National Oceanic and Atmospheric Administration (NOAA), before being harvested in the Fall.

The optimum temperature for a potato’s above-ground stems and leave to grow, according to a 2019 study, is 75°F. The optimum temperature for maximum tuber yields is 68°F; this is why most potatoes are grown in northern states.

Warm temperatures pose a significant risk to potatoes, and in turn, our French fries.

The reason our favorite spud fries so well is because of their high starch content. High temperatures cause uneven starch-to-sugar conversion in Russet Burbank potatoes; this leads to brown, burnt-looking ends when fried.

High heat and non-enough water can cause bumps and other malformations to form on the tubers.

Research has found that potatoes are not able to fight diseases well at higher temperatures. USDA researchers have found that most diseases that impact potatoes thrive in specific temperature ranges. One fungal disease, verticillium wilt, loves temperatures between 80 and 85°F. Late blight, which caused the Irish potato famine, likes temperatures between 65 and 68°F. As temperatures change, the threat of diseases will also shift.

Average temperatures across the United States have been gradually warming. Daytime average highs in July across central Wisconsin have risen more than 1.5°F per decade, according to the USDA. In Idaho’s Snake River Plain, where farmers cultivate most of the state’s crops, July’s daytime highs have risen more than 2°F per decade.

Most potatoes have low drought tolerance. Areas farmers grow potatoes in Idaho and Washington are quite dry; this means that proper irrigation is necessary here. Between 1986 and 2015, annual precipitation rates over the western U.S. decreased. One study found that the potato growing season in Washington and Idaho most likely will get longer based on irrigation demands and water stress. A longer growing season means more evapotranspiration would increase. Warmer temperatures and more evapotranspiration may lead to more crop stress and irrigation demands. All of this may lead to smaller tubers and, eventually, smaller fries.

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