Rising CO2 poses significant threat to human nutrition

http://news.harvard.edu/gazette/story/2014/05/rising-co2-poses-significant-threat-to-human-nutrition/

By Todd Datz, Harvard School of Public Health Communications
Other HSPH authors include Antonella Zanobetti, Itai Kloog, and Joel Schwartz.
May 7, 2014

At the elevated levels of atmospheric CO2 anticipated by around 2050, crops that provide a large share of the global population with most of their dietary zinc and iron will have significantly reduced concentrations of those nutrients, according to a new study led by Harvard School of Public Health (HSPH). Given that an estimated 2 billion people suffer from zinc and iron deficiencies, resulting in a loss of 63 million life years annually from malnutrition, the reduction in these nutrients represents the most significant health threat ever shown to be associated with climate change.

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The researchers analyzed data involving 41 cultivars (genotypes) of grains and legumes from the C3 and C4 functional groups (plants that use C3 and C4 carbon fixation) from seven different FACE locations in Japan, Australia, and the United States. The level of CO2 across all seven sites was in the range of 546 to 586 parts per million (ppm). The researchers tested the nutrient concentrations of the edible portions of wheat and rice (C3 grains), maize and sorghum (C4 grains), and soybeans and field peas (C3 legumes).

The results showed a significant decrease in the concentrations of zinc, iron, and protein in C3 grains. For example, zinc, iron, and protein concentrations in wheat grains grown at the FACE sites were reduced by 9.3 percent, 5.1 percent, and 6.3 percent, respectively, compared with wheat grown at ambient CO2. Zinc and iron were also significantly reduced in legumes; protein was not.

The finding that C3 grains and legumes lost iron and zinc at elevated CO2 is significant. Myers and his colleagues estimate that 2 billion–3 billion people around the world receive 70 percent or more of their dietary zinc and/or iron from C3 crops, particularly in the developing world, where deficiency of zinc and iron is already a major health concern.

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