Most news regarding the havoc wrought by climate change focuses on the future, but a study published in the online journal, Science Now, last week indicates that global rising temperatures are already affecting the production of four major food crops.
David Lobell, an assistant professor of environmental earth science at Stanford University, and Wolfram Schlenker, an agricultural economist at Columbia University, found that rising temperatures and decreases in rainfall have had an impact on wheat, corn, rice, and soybeans: key crops that account for approximately 75 percent of calories consumed by people worldwide.
The researchers looked at crop and climate data from 1980 to 2008, factoring in historical temperature and precipitation figures and their connection to wheat, corn, rice and soy yields, independent of improvements through better farming. Reviewing how yields changed from year to year and the increase in temperatures, the study found that rice and soybean cops were little affected by climate change. But overall global wheat production is down by more than five percent of what it would have been with no warming trend, and corn crops are down nearly four percent. The study found that temperature trends varied dramatically by region and had corresponding effects on crop production.
The United States, Canada, and Northern Mexico have not experienced any decrease in crops, nor have temperatures risen in those regions. Lobell said in the online Science article that this is consistent with information from the Intergovernmental Panel on Climate Change (IPCC) showing that for unknown reasons, the eastern part of the U.S. has not warmed as much as other parts of the world.
According to the researchers, this trend could have a significant impact on the economies of many countries and the welfare of their inhabitants; computer models show that each increase of a single degree in global temperatures can result in a five-percent drop in production of those crops. In an email interview Lobell said that corresponding higher food prices could have direct consequences to health, pointing out that fewer calories consumed could lead to more malnutrition and illness.
But skeptics make the point that improvements in roads, markets, and faming can increase the availability of crops despite warming, and people can adapt to low levels of change. According to an article in the Washington Post, Ken Cassman, an agronomist at the University of Nebraska, was quoted, saying, “It’s not clear how well these analyses are capturing how well farmers can respond, and have been responding, to changing temperatures.”
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