Increasing CO2 threatens human nutrition

  • Samuel S. Myers, Antonella Zanobetti, Itai Kloog, Peter Huybers, Andrew D. B. Leakey, Arnold J. Bloom, Eli Carlisle, Lee H. Dietterich, Glenn Fitzgerald, Toshihiro Hasegawa, N. Michele Holbrook, Randall L. Nelson, Michael J. Ottman, Victor Raboy, Hidemitsu Sakai, Karla A. Sartor, Joel Schwartz, Saman Seneweera, Michael Tausz, Yasuhiro Usui
This article was originally published in Nature.
Dietary deficiencies of zinc and iron are a substantial global public health problem. An estimated two billion people suffer these deficiencies, causing a loss of 63 million life-years annually. Most of these people depend on C3 grains and legumes as their primary dietary source of zinc and iron. Here we report that C3 grains and legumes have lower concentrations of zinc and iron when grown under field conditions at the elevated atmospheric CO2 concentration predicted for the middle of this century. C3 crops other than legumes also have lower concentrations of protein, whereas C4 crops seem to be less affected. Differences between cultivars of a single crop suggest that breeding for decreased sensitivity to atmospheric CO2 concentration could partly address these new challenges to global health.

Introduction

In the 1990s, several investigators found that elevated atmospheric CO2 concentration (hereafter abbreviated to [CO2]) decreased the concentrations of zinc, iron and protein in grains of wheat, barley and rice grown in controlled-environment chambers. However, subsequent studies failed to replicate these results when plants were grown in open-top chambers and free-air CO2 enrichment (FACE) experiments. A previous study found no effect of [CO2] on the concentrations of zinc or iron in rice grains grown under FACE and suggested that the earlier findings had been influenced by ‘pot effects’, by which a small rooting volume led to nutrient dilution at the root–soil interface. Of the more recent studies, most have indicated lower elemental concentrations in soybeans, sorghum, potatoes, wheat or barley grown at elevated [CO2], but with the exception of iron in one study on wheat, these results were statistically insignificant, perhaps because of small sample sizes.

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