The relationship between climate change and food security is hardly a new topic. But a new study examining the impact of rising temperatures on crop yields puts a terrifyingly fine point on the conversation.
Among the more sobering conclusions: Half of the country's corn harvest could be wiped out by 2100 without efficient reductions in greenhouse gases. Meanwhile, production of soybeans and wheat could fall by 40 percent and 20 percent, respectively.
“Projections tell us that in the U.S., these crops will suffer from hotter days," lead author Bernhard Schauberger told Scientific American. "Since these days will get more frequent with climate change, there will be harvest losses."
The study, published last week in the journal Nature Communications, noted the impact of such a scenario would reach far beyond U.S. borders — potentially affecting commodity prices globally and hurting food security in developing countries that rely on American exports.
This is how it works: As the earth warms, evaporation rates increase -- drawing moisture out of the soil and leaving less for thirsty plants. Meanwhile, thirsty plants try to cope by allocating more of their energy to root-growth and closing their pores to prevent water from escaping. The problem is that all of this root growth comes at the expense of stems, leaves and fruits, and water retention comes only at the expense of carbon dioxide uptake — which is essential for photosynthesis and growth.
The result: Every day the temperature soars above 86 degrees Fahrenheit (30 degrees Celsius) means a decline in yields.
Authors of the Potsdam study said increased irrigation could safeguard crops, but only to a point. After the temperature climbs above 97 degrees Fahrenheit, all bets are off.
The problem gets even thornier in regions where water scarcity is already an issue — a category likely to expand considerably as the world's population increases and water demand soars.
“There are lots of irrigated parts of the world, like northern India, which are already starting to run out of resources," the University of Chicago's Joshua Elliot, one of the report's co-authors, told Scientific American.
"Some estimates say there will be widespread irrigation deficits in the next 20 years — and then you have a double-whammy effect, where temperatures are increasing and you don't have the water you need to irrigate your crops.”
At least one genetically engineered, drought-tolerant crop is already on the market in the U.S.: DroughtGard, a corn hybrid created by Monsanto, was approved for sale in 2011 and has so far achieved mixed results. The plant has also been green-lighted in Australia, Canada, Mexico and Japan.
Meanwhile, in Argentina, a researcher has developed a genetically modified soybean she claims can increase yields by 14 percent during drought. The product has already been approved for sale in Argentina and is now undergoing field trials in the U.S.
While these developments hold potential, any discussion of genetically modified organisms also raises controversy — both due to the possibility of unforeseen ecological consequences and the risk of farmers becoming dependent on big corporations for their feed stock.
For the time being, Elliot told Scientific American, these technologies are simply too unproven to be relied upon as a fail-safe. More likely, farmers will cope by moving their operations to friendlier climates. As the nation's agricultural geography shifts, the Corn Belt will likely move northward, and the farm fields of the South fall fallow.
“Parts of Iowa could be growing cotton," Elliot said, "and the Deep South — where cotton is currently grown — will probably be too hot to grow anything.”
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