State of the Planet

News from the Columbia Climate School


A Climate Tipping Point for World Food Prices?

The United States is the world's largest grower of corn.

Increased growing-season heat due to climate change in coming decades could push staple U.S. crops off a cliff, and cause world food prices to jump, a Columbia University economist told a press briefing at a top scientific meeting this week.

In a panel organized by the American Association for the Advancement of Science, economist Wolfram Schlenker of the university’s School of International and Public Affairs noted that 75 percent of the calories humans consume come from just four crops—corn, soy, wheat and rice—and that nearly a quarter of these are produced in the United States, mostly in the Midwest. That share of the food market exceeds Saudi Arabia’s share of the oil market, he said. Yields have gone up three or four times since the 1940s, due to advances in breeding and growing techniques, and increased heat in coming decades could help some crops grow even more vigorously—but only up to a point.  An earlier county-county study of U.S. agriculture suggests that eventually, a tipping point will be reached, after which yields of major crops would plummet 30 to 80 percent. Specifically, a daily growing-season average of 30 degrees C (86 F) seems to be the limit, unless new heat-resistant varieties are developed. The economic results would ripple across the globe, says a new working paper by Schlenker and Michael J. Roberts of North Carolina State University. “So far, we’re really good at breeding stuff to increase yields, but we have done nothing to adjust to sensitivity to heat,” he said. “There is a severe supply-side danger, because we don’t invest enough in research.”

Schlenker told the audience that the picture is exacerbated by two demand factors. One is rising worldwide consumption of meat, which requires 20 times more cereal to produce the same amount of calories that people ultimately consume. The other is increasing diversion of food crops into ethanol, which now consumes 5 percent of food crops.  He called for the U.S. government to end subsidies and mandates for ethanol. “It is not necessarily a good thing for world food prices,” he said.  

Roger Beachy, another member of the panel, quickly butted heads with Schlenker over the ethanol issue.  Beachy, a top food scientist who helped create the first genetically modified crops and who until recently headed the Obama administration’s National Institute of Food and Agriculture, said that mandates to use ethanol had to remain. “We need options for farmers to go into different markets, so they can remain economically strong,” he said. Beachy cited competition from other major producers such as Brazil, which produces large amounts of sugar cane for ethanol. Schlenker retorted that prices for some food commodities have already double or tripled in the past few years. “I’m not worried about farm prices, because farmers are doing fine,” he said. “I’m worried about consumers.”

The exchange was part of an overall briefing on emerging risks in the global food system. The briefing can be viewed here.

MacLean’s magazine article on the debate

Banner featuring a collage of extreme heat images.

Recent record-breaking heat waves have affected communities across the world. The Extreme Heat Workshop will bring together researchers and practitioners to advance the state of knowledge, identify community needs, and develop a framework for evaluating risks with a focus on climate justice. Register by June 15

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