Impact of anthropogenic CO2 emissions on global human nutrition


Atmospheric CO2 is on pace to surpass 550 ppm in the next 30–80 years. Many food crops grown under 550 ppm have protein, iron and zinc contents that are reduced by 3–17% compared with current conditions. We analysed the impact of elevated CO2 concentrations on the sufficiency of dietary intake of iron, zinc and protein for the populations of 151 countries using a model of per-capita food availability stratified by age and sex, assuming constant diets and excluding other climate impacts on food production. We estimate that elevated CO2 could cause an additional 175 million people to be zinc deficient and an additional 122 million people to be protein deficient (assuming 2050 population and CO2 projections). For iron, 1.4 billion women of childbearing age and children under 5 are in countries with greater than 20% anaemia prevalence and would lose >4% of dietary iron. Regions at highest risk—South and Southeast Asia, Africa, and the Middle East—require extra precautions to sustain an already tenuous advance towards improved public health.

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Fig. 1: Historical trends in CO2 emissions and atmospheric concentrations compared with model forecasts to 2100.
Fig. 2: Risk of inadequate nutrient intake from elevated atmospheric CO2 concentrations of 550 ppm.
Fig. 3: Correlations between iron, zinc and protein density of plant- and animal-sourced foods.
Fig. 4: Consumption of animal and vegetal foods by income category for the highest-risk countries.


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This work was supported by Weston Foods US, Inc. (grant no. 207390 to M.R.S.) and by the Wellcome Trust ‘Our Planet, Our Health’ programme (grant no. 106924 to S.S.M.).

Author information




M.R.S. contributed to the study design, data acquisition, review and interpretation of the results, execution of the analysis and writing of the manuscript. S.S.M. contributed to the study design, review and interpretation of the results, and editing of the manuscript.

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Correspondence to Matthew R. Smith.

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Supplementary information

Table S1

Composite table of the zinc and phytate values used, in units of mg per 100 g of edible portion of each food. Entries from each individual table are given, and the composite values with their original sources are in the far right columns. Full reference information is available in the Methods

Table S2

Food groupings used to estimate the response of elevated CO2 on nutrient content across broader categories

Table S3

Percentage declines in nutritional content of each food (with 95% confidence intervals)

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Smith, M.R., Myers, S.S. Impact of anthropogenic CO2 emissions on global human nutrition. Nature Clim Change 8, 834–839 (2018).

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