Increasing CO2 threatens human nutrition

Journal name:
Nature
Volume:
510,
Pages:
139–142
Date published:
DOI:
doi:10.1038/nature13179
Received
Accepted
Published online

Dietary deficiencies of zinc and iron are a substantial global public health problem. An estimated two billion people suffer these deficiencies1, causing a loss of 63million life-years annually2, 3. 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.

At a glance

Figures

  1. Percentage change in nutrients at elevated [lsqb]CO2[rsqb] relative to ambient [lsqb]CO2[rsqb].
    Figure 1: Percentage change in nutrients at elevated [CO2] relative to ambient [CO2].

    Numbers in parentheses refer to the number of comparisons in which replicates of a particular cultivar grown at a specific site under one set of growing conditions in one year at elevated [CO2] have been pooled and for which mean nutrient values for these replicates are compared with mean values for identical cultivars under identical growing conditions except grown at ambient [CO2]. In most instances, data from four replicates were pooled for each value, meaning that eight experiments were combined for each comparison (see Table 1 for details of experiments). Error bars represent 95% confidence intervals of the estimates.

  2. Percentage change (with 95% confidence intervals) in nutrients at elevated [lsqb]CO2[rsqb] relative to ambient [lsqb]CO2[rsqb], by cultivar.
    Figure 2: Percentage change (with 95% confidence intervals) in nutrients at elevated [CO2] relative to ambient [CO2], by cultivar.

    a, Zinc; b, iron; c, protein.

Tables

  1. Percentage change in nutrient content at elevated [lsqb]CO2[rsqb] relative to ambient [lsqb]CO2[rsqb]
    Extended Data Table 1: Percentage change in nutrient content at elevated [CO2] relative to ambient [CO2]
  2. Original data combined with previously published FACE data from studies 3, 4, 6 and 7
    Extended Data Table 2: Original data combined with previously published FACE data from studies 3, 4, 6 and 7
  3. Original data combined with previously published FACE and chamber data from studies 1-10
    Extended Data Table 3: Original data combined with previously published FACE and chamber data from studies 1–10
  4. Percentage change in nutrient content at elevated [lsqb]CO2[rsqb] compared with ambient [lsqb]CO2[rsqb] for all nutrients
    Extended Data Table 4: Percentage change in nutrient content at elevated [CO2] compared with ambient [CO2] for all nutrients
  5. Countries whose populations receive at least 60% of dietary iron and/or zinc from C3 grains and legumes
    Extended Data Table 5: Countries whose populations receive at least 60% of dietary iron and/or zinc from C3 grains and legumes
  6. Literature reporting nutrient changes in the edible portion of crops grown at elevated and ambient [lsqb]CO2[rsqb]
    Extended Data Table 6: Literature reporting nutrient changes in the edible portion of crops grown at elevated and ambient [CO2]

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Author information

Affiliations

  1. Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, 02215, USA

    • Samuel S. Myers,
    • Antonella Zanobetti &
    • Joel Schwartz
  2. Harvard University Center for the Environment, Cambridge, Massachusetts 02138, USA

    • Samuel S. Myers
  3. The Department of Geography and Environmental Development, Ben-Gurion University of the Negev, PO Box 653, Beer Sheva, Israel

    • Itai Kloog
  4. Department of Earth and Planetary Science, Harvard University, Cambridge, Massachusetts 02138, USA

    • Peter Huybers
  5. Department of Plant Biology and Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

    • Andrew D. B. Leakey
  6. Department of Plant Sciences, University of California at Davis, Davis, California 95616, USA

    • Arnold J. Bloom &
    • Eli Carlisle
  7. University of Pennsylvania, Department of Biology, Philadelphia, Pennsylvania 19104, USA

    • Lee H. Dietterich
  8. Department of Environment and Primary Industries, Horsham, Victoria 3001, Australia

    • Glenn Fitzgerald
  9. National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki, 305-8604, Japan

    • Toshihiro Hasegawa,
    • Hidemitsu Sakai &
    • Yasuhiro Usui
  10. Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA

    • N. Michele Holbrook
  11. United States Department of Agriculture Agricultural Research Service, Soybean/Maize Germplasm, Pathology, and Genetics Research Unit, Department of Crop Sciences, University of Illinois, Urbana, Illinois 61801, USA

    • Randall L. Nelson
  12. School of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA

    • Michael J. Ottman
  13. United States Department of Agriculture Agricultural Research Service, Aberdeen, Idaho 83210, USA

    • Victor Raboy
  14. The Nature Conservancy, Santa Fe, New Mexico 87544, USA

    • Karla A. Sartor
  15. Department of Agriculture and Food Systems, Melbourne School of Land and Environment, The University of Melbourne, Creswick, Victoria 3363, Australia

    • Saman Seneweera
  16. Department of Forest and Ecosystem Science, Melbourne School of Land and Environment, The University of Melbourne, Creswick, Victoria 3363, Australia

    • Michael Tausz

Contributions

S.S.M. conceived the overall project and drafted the manuscript. A.Z., I.K., J.S. and P.H. performed statistical analyses. P.H. and A.D.B.L. provided substantial input into methods descriptions. A.J.B., E.C. and V.R. analysed grain samples for nutrient content. G.F., T.H., A.D.B.L., R.L.N., M.J.O., H.S., S.S., M.T. and Y.U. conducted FACE experiments and supplied grain for analysis. N.M.H. and P.H. assisted with elements of experimental design. K.A.S. and L.H.D. assisted with data collection and analysis. All authors contributed to manuscript preparation.

Competing financial interests

The authors declare no competing financial interests.

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Comments

  1. Report this comment #63379

    Anand Ramanathan said:

    The article "Increasing CO2 threatens human nutrition", Nature 510, 139?142 (05 June 2014) examines an important research question, but has a misleading title. In our opinion, the misleading title, while it makes the case for reducing carbon emissions, does a disservice to science overall. Journal articles are meant to be objective and cannot have claims that are not accurate, particularly in the title. Misleading claims, particularly in mainstream journals, can feed into the popular perception of scientists being biased, in this case about carbon emissions and climate change.

    The authors generously estimate 2.3 billion people to be at risk of zinc or iron deficiency due to their dependence on C3 grains and legumes. With a full two-thirds of the world's population (including the developed world) not being counted, the phrase "threatens human nutrition" is misleading. Another misrepresentation is terming two micronutrients, zinc and iron as "nutrition", which is a broad term that includes macronutrients such as carbohydrates, fats and proteins as well as micronutrients like calcium, iodine and several vitamins.

    In trying to connect decreased zinc and iron concentrations (from enhanced CO2) and additional disease burden, the authors also fail to ask a natural question for those familiar with free-air CO2 enrichment (FACE) experiments ? Is there an overall increase in plant productivity due to elevated CO2 levels that may offset the reduced nutrient concentration?

    As carbon researchers ourselves who have seen CO2 levels rise firsthand, we are concerned about increased atmospheric CO2. However, while we are all free to write editorials, opinion pieces and blogs, as scientists we must adhere to the science when it comes to journal articles so that the science community as a whole maintains credibility.

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