Rising Carbon Emissions Could Cause Massive Malnutrition As Zinc And Iron Are Depleted From Crops

By Matthew Mientka on May 7, 2014 1:06 PM EDT

Rising carbon levels from human activity may soon reduce levels of zinc and iron found in food crops around the globe. Photo courtesy of Andrea Della Adriana, CC BY 2.0.
Rising carbon levels from human activity may soon reduce levels of zinc and iron found in food crops around the globe. Photo courtesy of Andrea Della Adriana, CC BY 2.0.

Rising carbon levels may cause massive malnutrition among people who depend on dietary zinc and iron from crops susceptible to the ravages of global climate change.

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By 2050, a large proportion of the global population may be affected by the depletion of nutrients in dietary staples such as wheat, rice, maize, and soybeans. The scale of such a Malthusian catastrophe may be gleaned by looking at today's level of global malnutrition. Two billion people around the world suffer deficiencies of zinc and iron annually, leading to the loss of 63 million life years.

"This study is the first to resolve the question of whether rising CO2 concentrations -- which have been increasing steadily since the Industrial Revolution -- threaten human nutrition," says Samuel Myers, a Harvard researcher whose study was published Wednesday in the journal Nature.

The dire forecast for future malnutrition follows the White House's release yesterday of a major climate assessment agreeing with the United Nation's opinion that global climate change is real and has been driven largely by carbon and methane emissions from human activity in this "anthropocene era." With Republicans expected to retake the U.S. Senate in upcoming midterm elections, President Barack Obama said on Monday he would use executive power to bypass Congress on U.S. strategy to manage the effects of global climate change - at times one of denial.

Indeed, China's English-language news network took the occasion on Wednesday to report on America's reaction to news that global climate change was already affecting the United States, with a noticeable increase during the past 50 years in heavy seasonal rains throughout New England.

The Nature study builds on past work showing an inverse relationship of elevated carbon levels to reductions in crop nutrients. Yet the literature on the subject is already dated as some studies were criticized for using artificial growing conditions. Even when experimenters used free-air carbon dioxide enrichment technology, the sample sizes were too small to draw good conclusions.

Here, Myers put his team to work analyzing data from 41 "cultivars," or genotypes, of grains legumes from plants using C3 and C4 carbon. Drawing these foods from seven sites across Japan, Australia, and the U.S., the researchers tested the edible wheat and rice, maize and sorghum, as well as soybeans and field peas. With no doubt, higher levels of carbon emissions significantly reduced the nutritional value of foods from these crops. Levels of zinc, iron, and protein in wheat grains fell by 9.3 percent, 5.1 percent, and 6.3 percent compared to wheat grown at today's "normal" level of atmospheric carbon. Likewise, zinc and iron levels fell in legumes exposed to higher amounts of ambient carbon, though protein levels were unaffected.

Myers says the implications of higher carbon emissions may be enormous as the world's population surges to some 9 billion by mid-century. Already, 2-3 billion people satisfy 70 percent or more of their dietary zinc and iron requirement with crops sensitive to C3 -- mostly people in the developing world.

"Humanity is conducting a global experiment by rapidly altering the environmental conditions on the only habitable planet we know," Mayers said in a press statement. "As this experiment unfolds, there will undoubtedly be many surprises. Finding out that rising CO2 threatens human nutrition is one such surprise."

Among possible strategies for adapting to global warming may be greater production of crops less sensitive to higher levels of atmospheric carbon, such as legumes or cultivars of rice found less sensitive to zinc and iron losses than similar varieties. Inevitably, part of the world's solution to global warming may involve the "biofortification" of crops through genetic engineering, as well as wide-scale nutritional supplements for the world population.

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