December 11th, 2012 by James Ayre
As atmospheric carbon dioxide levels rise they are having an increasingly negative effect on the nutritional quality of wheat, new research from
the University of Gothenburg has found.
The protein content of wheat has been falling significantly as carbon dioxide levels have been rising. This is a important finding. The scale of agriculture is likely going to contract greatly as the effects of climate change, deforestation, increasing water scarcity, and the failing of many widely used pesticides and herbicides, continues and worsens. With all of these other problems appearing inevitably in the near future, adding in a loss of nutritional quality in the crops that do manage to be grown, and not wiped out by storms, drought, pestilence, disease, and ‘weeds’, is very significant.
“Elevated levels of atmospheric carbon dioxide stimulate the photosynthesis and growth of most plants. However, unless plants increase their uptake of nutrients to a corresponding degree, their yields will have a lower nutritional value. A lower level of the nutrient nitrogen results in a lower protein content, and thus poorer nutritional quality.”
“Protein content is the most important quality aspect for crops, with implications for both nutritional value and the baking properties of the grain,” explains Håkan Pleijel, Professor of Environmental Science at the University of Gothenburg’s Department of Biological and Environmental Sciences.
“Researchers Håkan Pleijel and Johan Uddling have summarized the way in which experimentally elevated carbon dioxide levels affect the harvest index and protein content of wheat. The study includes 43 field experiments with 17 different varieties of wheat, carried out in ten countries across four continents.”
The results are very clear:
“Elevated carbon dioxide levels often increase the size of the grain yield, but also lead to a reduction in quality in the form of lower protein content,” says Professor Pleijel.
“Wheat — together with rice — is the world’s most important crop in quantitative terms. Wheat grain is also unusually rich in protein, and wheat is the crop that provides the human race with the most protein. Reduced protein content as a result of elevated carbon dioxide levels is therefore a serious negative consequence of ongoing atmospheric change.”
“One reason why the protein content of wheat grain drops as carbon dioxide levels rise is that nitrogen uptake does not keep pace with the increased growth of the wheat grain — a kind of dilution effect. However, elevated carbon dioxide levels reduce the protein content of wheat even when the size of the wheat yield is unaffected.”
“This indicates that carbon dioxide has a negative impact on plants’ ability to absorb nitrogen,” continues Professor Pleijel. “This is a novel and unexpected finding, and is something we need to study in greater depth in order to understand the causes.”
“Laboratory studies have shown that elevated carbon dioxide levels can disrupt the process whereby plants convert the inorganic nitrogen molecule nitrate into the forms of nitrogen found in proteins.”
“Johan Uddling and Professor Pleijel are currently investigating whether the effects they have demonstrated in wheat are also seen in other crops.”
“Our results indicate that reduced nitrogen and protein content as a result of elevated carbon dioxide levels is a general response in crops, and cannot be countered simply through increased fertilization,” adds Uddling.
“The overall positive effect of elevated carbon dioxide levels on grain yield therefore has a downside in the form of a reduction in the nutritional quality of our most important foodstuff.”
“This is a serious consequence of rapidly rising global carbon dioxide levels on global food security,” concludes Professor Pleijel.
The new research was just published in the journal Global Change Biology.
Source: University of Gothenburg
Image Credits: Wheat via Wikimedia Commons
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