Study: Global warming will cut wheat yields
OSLO — Global warming will reduce average wheat yields by 6 percent for every 1.8-degree increase in temperature, a study by a U.S.-led team of scientists said today.
That would be a bigger-than-expected brake on food production.
The decrease would be 46.2 million tons from a harvest of 771 million tons of wheat worldwide in 2012, highlighting a need to breed more heat-tolerant crops.
In recent decades, wheat yields have declined in hotter sites such as India, Africa, Brazil and Australia, more than offsetting yield gains in some cooler places, including parts of the United States, Europe and China, the study showed.
“Global wheat production is estimated to fall by 6 percent for each degree Celsius — 1.8 degrees Fahrenheit — of further temperature increase,” according to the scientists, who used wheat-crop computer models and field experiments.
They said there are many options to limit the damage from higher temperatures involving the development of wheat types that tolerate additional heat, especially in warm regions.
The study examined only temperatures, not carbon dioxide, the main greenhouse gas emitted by the burning of fossil fuels. Carbon dioxide is an airborne fertilizer.
The study also did not try to assess possible changes in rainfall patterns.
“Wheat-yield declines in response to temperature impacts only are likely to be larger than previously thought and should be expected earlier, starting even with small increases in temperature,” the researchers wrote.
Joergen Eivind Olesen, a professor at the University of Aarhus in Denmark, was one of the authors. He said the focus on temperature alone meant the study “is not the complete picture.”
“Even so, in many parts of the world, there would still be a decrease in yields” even with small temperature rises, he said.
In March, the U.N.’s Intergovernmental Panel on Climate Change projected that yields of wheat, rice and maize would fall overall with temperature increases of 3.6 degrees Fahrenheit above late 20th century levels — a higher threshold than in yesterday’s study.
Average world temperatures have risen by about 1.5 degrees since the Industrial Revolution and are projected to rise by between 0.5 and 8.6 degrees in this century, depending on whether governments reduce emissions.
http://www.dispatch.com/content/stories/business/2014/12/23/study-global-warming-will-cut-wheat-yields.html
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