Food Security

18th June 2015

Graham Readfearn reports in The Guardian (17/6/15):

" ... several studies have found that something else also happens as the atmosphere gets loaded with more CO2. As the carbon dioxide levels go up, the protein in the plants tends to go down. Last year, a study in Nature found that wheat and rice grown outside under higher concentrations of CO2 both had reduced levels of zinc and iron, as well as protein. 

"A new study published in recent weeks was another reminder that not only can increased CO2 be a problem for food security through climate change, but it can also directly impact the nutritional value of crops. Published in the journal Global Change Biology, scientists looked closely at the amount of nitrogen - a proxy for protein - in plants growing at atmospheric levels of CO2 similar to those we’re heading for in the middle part of this century. The study examined data from a series of experiments run independently in countries including the US, Italy, Germany, New Zealand and China, where open air croplands, grasslands and forests are subjected to increased levels of CO2 (usually by adding the gas to the experimental areas through pipes).

"Like previous studies, this one also found that while increased levels of CO2 in the atmosphere helped some plants grow faster, it also cut the amount of nitrogen (protein) in plants. But this study also found the reduction in protein happened even for those plants that didn’t get a growth boost from the added CO2. The crops covered in the study were rice, wheat and sorghum – all key sources of protein in the world’s food supply. ... But just how much less protein do those plants have? The study suggests a figure of about 10 per cent. The IPCC report on climate impacts pointed to several studies that found cereals grown under higher CO2 conditions had less protein. One study on wheat, rice, barley and potatoes grown at higher CO2 levels found that protein was reduced by between 10 and 14 per cent."

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