Increasing CO2 threatens human nutrition

Authors: MYERS, SAMUEL - Harvard School Of Public Health; ZANOBETTI, ANTONELLA - Harvard School Of Public Health; KLOOG, ITAI - Ben Gurion University Of Negev; HUYBERS, PETER - Harvard University; LEAKEY, ANDREW - University Of Illinois; BLOOM, ARNOLD - University Of California; CARLISLE, ELI - University Of California; DIETTERICH, LEE - University Of Pennsylvania; FITZGERALD, GLENN - Department Of Environment And Primary Industries; HASEGAWA, TOSHIHIRO - National Institute For Agro-Environmental Sciences; HOLBROOK, N - Harvard University; Nelson, Randall; OTTMAN, MICHAEL - University Of Arizona; Raboy, Victor; SAKAI, HIDEMITSU - National Institute For Agro-Environmental Sciences; SARTOR, KARLA - Nature Conservancy; SCHWARTZ, JOEL - Harvard School Of Public Health; SENEWEERA, SAMAN - University Of Melbourne; TAUSZ, MICHAEL - University Of Melbourne; USUI, YASUHIRO - National Institute For Agro-Environmental Sciences

Submitted to: Nature
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2014
Publication Date: 6/5/2014
Publication URL: http://handle.nal.usda.gov/10113/60214
Citation: Myers, S.S., Zanobetti, A., Kloog, I., Huybers, P., Leakey, A., Bloom, A.J., Carlisle, E., Dietterich, L.H., Fitzgerald, G., Hasegawa, T., Holbrook, N.M., Nelson, R.L., Ottman, M.J., Raboy, V., Sakai, H., Sartor, K.A., Schwartz, J., Seneweera, S., Tausz, M., Usui, Y. 2014. Increasing CO2 threatens human nutrition. Nature. 150:139. DOI:10.1038/nature13179.

Interpretive Summary: Dietary deficiencies of zinc and iron are a major 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 upon grains and legumes as their primary dietary source of zinc and iron. Our research analyzed 540 pairs of crop samples grown at contemporary and elevated atmospheric CO2 from six different experiments involving six food crops. We tested the nutrient concentrations of the edible portions of rice (18 varieties), wheat (8 varieties), maize (2 varieties), soybeans (7 varieties), field peas (4 varieties) and sorghum (1 variety). In all six experiments, the elevated CO2 was in the range of 550-584 ppm. Each crop sample grown at elevated CO2 was paired with an identical cultivar grown under the same conditions but at contemporary CO2 levels. We found that elevated CO2 was associated with significant decreases in the concentrations of zinc and iron in some grasses and all legumes. For example, in wheat grains grown at elevated CO2 compared with contemporary CO2, zinc decreased 9.6% and iron decreased 5.2%. We also found that elevated CO2 was associated with lower protein in some grasses with a 6.5% decrease in wheat grains and a 7.9% decrease in rice grains. Response differences between cultivars suggest breeding crops for reduced sensitivity to elevations in atmospheric CO2. Such breeding efforts may partly address the new challenges to global health that these findings highlight. This research will be of interest to crop breeders, physiologist and all those interested in the effects of climate change.

Technical Abstract: Dietary deficiencies of zinc and iron are a major 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 upon grains and legumes as their primary dietary source of zinc and iron. This manuscript reports findings from the analysis of 540 pairs of crop samples grown at contemporary and elevated [CO2] from six different FACE experiments involving six food crops. We tested the nutrient concentrations of the edible portions of rice (Oryza sativa, 18 cultivars), wheat (Triticum aestivum, 8 cultivars), maize (Zea mays, 2 cultivars), soybeans (Glycine max, 7 cultivars), field peas (Pisum sativum, 4 cultivars) and sorghum (Sorghum bicolor, 1 cultivar). In all six experiments, the elevated [CO2] was in the range of 550-584 ppm. Each crop sample grown at elevated [CO2] was paired with an identical cultivar grown under the same conditions but at contemporary [CO2]. Our main outcomes were fractional changes in concentrations of the nutrients between samples grown at elevated and contemporary [CO2] levels, estimated using a linear mixed effects statistical model. We found that elevated [CO2] was associated with significant decreases in the concentrations of zinc and iron in all C3 grasses and legumes. For example, in wheat grains grown at elevated [CO2] compared with contemporary [CO2], zinc decreased 9.6% and iron decreased 5.2%. We also found that elevated [CO2] was associated with lower protein in C3 grasses with a 6.5% decrease in wheat grains and a 7.9% (95% CI: -8.9, -6.9) decrease in rice grains. Elevated [CO2] showed no significant effect on protein in C3 legumes or C4 crops. Response differences between cultivars suggest breeding crops for reduced sensitivity to elevations in atmospheric [CO2]. Such breeding efforts may partly address the new challenges to global health that these findings highlight.