A new worldwide analysis of agricultural trends blames our warming global climate for a 3-5 percent decline in corn and wheat production during the last 30 years -- a period that saw a 6 percent rise in food prices.
The research, just published online by the journal Science, links yield declines in these two important food sources to temperature changes in major agricultural regions around the world -- with the singular exception of North America.
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Led by David B. Lobell, a Stanford University environmental modeler, the team was surprised to find that their data showed no warming trend and no climate-related crop production changes in the United States since 1980.
"In terms of temperature, what we see is North America seems, oddly enough, to be exhibiting almost no trend at all over the last 30 years, whereas places like Europe, China, Brazil, pretty much the rest of the world in terms of major agricultural producers, have seen major warming," Lobell said in a Science podcast interview.
The researchers recognized that many factors such as technology and management practices influence crop production levels, and in fact, said Lobell, "climate is not the predominant driver of change over long periods of time in crop production."
"The basic question of the study was: How important is climate?"
To isolate the influence of climate, the researchers constructed two models that were identical in all of the important crop-production variables for wheat, corn, rice and soybeans -- with the exception of climate. One model held climate conditions unchanged throughout the period beginning in 1980, the other model tracked the observed warming trends in the different production regions.
The model output identifies a global net climate-related loss of 5.5 percent for wheat and 3.8 percent for corn, while rice and soybean was largely unaffected by climate on a global scale -- gains in some countries offset losses in others. "Among the largest country-specific losses was wheat in Russia (almost 15 percent)," the scientists reported. "While the country with the largest overall share of crop production (United States) showed no effect due to the lack of significant climate trends."
IMAGE 1: The maps show the temperature and precipitation trends for the growing seasons from 1980 to 2008 for the predominant crop (corn, wheat, rice and soybean. Outside of the United States, 65 percent of the major producing countries showed a significant temperature trend. Overall, the changes in precipitation were less dramatic. (Image courtesy Science/American Association for the Advancement of Science.)
IMAGE 2: A farm in Australia with green plastic-wrapped bales of hay made from failed wheat crops. (Corbis)
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