Global Warming Has Cut Yields of Some Staple Crops, Study Says

Rising global temperatures have reduced yields of wheat and corn in some countries, a decline that probably has contributed to the rise in agricultural commodity prices in recent years, according to a study in the journal Science. Researchers from Stanford and Columbia universities said that from 1980 to 2008, temperature increases of several degrees Fahrenheit in key growing regions — including Russia, India, China, and France — had cut into yields of corn and wheat compared to expected yields had growing season temperatures not risen. Other key grain-growing nations, such as the U.S., have so far not experienced such increases and their yields remained unaffected, the study said. Overall, however, warming reduced production of corn and wheat by about 3 percent globally since 1980, likely adding about 6 percent to prices for those commodities, the study said. The impact of higher temperatures on production of rice and soybeans — the other two key staple crops — was negligible, according to the study. In all countries, rising CO2 levels helped stimulate crop growth, but the study said that effect is expected to be offset by losses from steadily rising temperatures.