Elevated atmospheric CO2 concentrations and climate change will affect our food's quality and quantity
Authors: Kristie L Ebi, Irakli Loladze
Journal: The Lancet Planetary Health (2019)

Greenhouse gas emissions are affecting the quantity and quality of our food in two ways. First, they are driving anthropogenic climate change, which decreases yields of major cereal crops in some regions. Increased temperatures, changes in precipitation patterns, increased ozone concentrations, and more frequent and extreme heatwaves, floods, and droughts can reduce crop yields, particularly in the tropics, with risks increasing with additional warming depending on the region.1Porter JR Xie L Challiinor AJ et al.Food security and food production systems.in: Field CB Barros VR Dokken DJ Climate change 2014: impacts, adaptation, and vulnerability. Part A: global and sectoral aspects. Contribution of working group II to the fifth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge and New York, NY2014: 485-533Google Scholar Lower crop yields increase stunting and wasting, particularly in low-income and middle-income countries.1Porter JR Xie L Challiinor AJ et al.Food security and food production systems.in: Field CB Barros VR Dokken DJ Climate change 2014: impacts, adaptation, and vulnerability. Part A: global and sectoral aspects. Contribution of working group II to the fifth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge and New York, NY2014: 485-533Google Scholar Second, increased concentrations of carbon dioxide (CO2)—by directly affecting plants—worsen the nutritional quality of food by decreasing protein and mineral concentrations by 5–15%, and B vitamins by up to a 30%.2Loladze I Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition.eLife. 2014; 3e02245Crossref PubMed Scopus (256) Google Scholar, 3Myers SS Zanobetti A Kloog I et al.Increasing CO2 threatens human nutrition.Nature. 2014; 510: 139-142Crossref PubMed Scopus (753) Google Scholar, 4Zhu C Kobayashi K Loladze I et al.Carbon dioxide (CO2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries.Sci Adv. 2018; 4eaaq1012Crossref PubMed Scopus (185) Google Scholar Higher CO2 concentrations increase photosynthesis in C3 plants (eg, wheat, rice, potatoes, barley), which can increase crop yields. But those increases come at the cost of lower nutritional quality as plants accumulate more carbohydrates and less minerals (eg, iron and zinc), which can negatively affect human nutrition.5Loladze I Rising atmospheric CO2 and human nutrition: toward globally imbalanced plant stoichiometry?.Trends Ecol Evol. 2002; 17: 457-461Summary Full Text Full Text PDF Scopus (290) Google Scholar Thus, accurately quantifying the effect of increasing CO2 concentrations on human nutrition requires accounting for changes in the quantity and quality of crop harvests and diets and economic parameters (eg, food prices). Decreases in the nutritional quality of crops related to CO2 will exacerbate current challenges. As of 2017, 821 million people globally are food insecure, with 22% of children (151 million) stunted and 7·5% (over 50 million) wasted.6Food and Agriculture Organization of the United NationsInternational Fund for Agricultural DevelopmentUNICEFWorld Food ProgrammeWHOThe state of food security and nutrition in the world. Building climate resilience for food security and nutrition. Food and Agriculture Organization of the United Nations, Rome2018: 202Google Scholar Micronutrient deficiencies cause a much larger burden of disease than food insecurity, with approximately 2 billion people having deficiencies in iron, zinc, and other micronutrients in 2003.6Food and Agriculture Organization of the United NationsInternational Fund for Agricultural DevelopmentUNICEFWorld Food ProgrammeWHOThe state of food security and nutrition in the world. Building climate resilience for food security and nutrition. Food and Agriculture Organization of the United Nations, Rome2018: 202Google Scholar These deficiencies adversely affect cognitive development, metabolism, obesity, diabetes, and other health outcomes, potentially affecting health and welfare across the life course. In The Lancet Planetary Health, Robert Beach and colleagues7Beach RH Sulser TB Crimmins A et al.Combining the effects of increased atmospheric carbon dioxide on protein, iron, and zinc availability and projected climate change on global diets: a modelling study.Lancet Planet Health. 2019; 3: e307-e317Summary Full Text Full Text PDF PubMed Scopus (62) Google Scholar accounted for projected climate change and fertilisation effects of CO2 on crop yields and projected CO2 effects on the concentrations of iron, zinc, and protein in crops between 2010 and 2050. Using a global economic model of the agricultural sector, they show that technological changes, market responses, and the fertilisation effects of CO2 on yields are projected to increase the global availability of dietary protein, iron, and zinc. The authors then used two independently derived datasets of the effects of increasing CO2 on crop quality: a subset of data restricted to edible tissues from Loladze (2014);2Loladze I Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition.eLife. 2014; 3e02245Crossref PubMed Scopus (256) Google Scholar and data supporting Myers et al (2014)3Myers SS Zanobetti A Kloog I et al.Increasing CO2 threatens human nutrition.Nature. 2014; 510: 139-142Crossref PubMed Scopus (753) Google Scholar with the wheat portion from Fernando (2013).8Fernando ND Wheat grain quality dynamics under elevated atmospheric CO2 concentration in Mediterranean climate conditions. The University of Melbourne, 2013Google Scholar All the data were restricted to nitrogen (as a proxy for protein), iron, and zinc. The authors combined these datasets with economic projections of shifts in global diets, crop production, food prices, and income to project decreases in global availability of protein, iron, and zinc of 2·5–4·1% by midcentury, compared with estimates that ignore the effects of increased CO2 on crop quality. These decreases are expected to slow progress in achieving reductions in global nutrient deficiencies, disproportionately affecting countries that already have high levels of nutritional deficieny. Other modeling estimates also project negative effects of increasing atmospheric CO2 concentrations on human nutrition by mid-century. Weyant and colleagues9Weyant C Brandeau ML Burke M Lobell DB Bendavid E Basu S Anticipated burden and mitigation of carbon-dioxide-induced nutritional deficiencies and related diseases: a simulation modeling study.PLoS Med. 2018; 15e1002586Crossref PubMed Scopus (29) Google Scholar accounted for climate change and dietary patterns to project that CO2-induced reductions in the concentrations of zinc and iron in crops alone could induce 125·8 million disability-adjusted life-years globally, with southeast Asian and sub-Saharan African countries being most affected. Smith and Myers10Smith MR Myers SS Impact of anthropogenic CO2 emissions on global human nutrition.Nat Clim Chang. 2018; 8: 834-839Crossref Scopus (183) Google Scholar assumed no changes in diets but accounted for decreases in nutrient content of crops to project that an additional 175 million people could become zinc deficient and an additional 122 million people could become protein deficient. Zhu and colleagues4Zhu C Kobayashi K Loladze I et al.Carbon dioxide (CO2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries.Sci Adv. 2018; 4eaaq1012Crossref PubMed Scopus (185) Google Scholar estimate that 600 million people will be at risk later this century in countries with the highest levels of rice consumption and the lowest overall gross domestic product per capita. Modeling efforts need to be expanded from focusing on iron and zinc to include other minerals essential for human nutrition, including calcium and magnesium, which also decrease in plants exposed to higher CO2 concentrations.2Loladze I Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition.eLife. 2014; 3e02245Crossref PubMed Scopus (256) Google Scholar The inclusion of these micronutrients is needed to quantify the total possible effect of increasing CO2 concentrations on human health. For example, about 3·5 billion people are at risk of dietary calcium deficiency, without considering the potential effects of increasing CO2 concentrations.11Kumssa DB Joy EJM Ander EL et al.Dietary calcium and zinc deficiency risks are decreasing but remain prevalent.Sci Rep. 2015; 510974Crossref PubMed Scopus (240) Google Scholar The magnitude of the health risks will be amplified when one considers the potential effects of increased concentrations of CO2 on livestock, which contribute more than 15% of the global human protein supply. To quantify the trajectory of nutritional stress in cattle from reduction of nitrogen availability in grasslands caused by increasing CO2 concentrations, Craine and colleagues12Craine JM Elmore A Angerer JP Long-term declines in nutritional quality for North American cattle.Environ Res Lett. 2017; 12044019Crossref Scopus (25) Google Scholar examined dietary quality over 22 years for US cattle, standardising for several factors, including forage quality, and showed that cattle have been increasingly protein-stressed, probably decreasing weight gain in cattle. The replacement costs of decreased protein provision were estimated to be the equivalent of US$1·9 billion annually. Increasing research indicates that undernutrition will be the greatest health risk of increasing CO2 concentrations and climate change. Solutions urgently need to be found to ensure the achievement of Sustainable Development Goal 2 on food security. IL's data, which were used by Beach and colleagues, are open access; he commented on the initial analyses by Beach and colleagues to ensure appropriate weighting and interpolating the results to various carbon dioxide concentrations, but had no further role in development of the manuscript. KLE declares no competing interests. Combining the effects of increased atmospheric carbon dioxide on protein, iron, and zinc availability and projected climate change on global diets: a modelling studyThis approach is an improvement in estimating future global food security by simultaneously projecting climate change effects on crop productivity and changes in nutrient content under increased concentrations of CO2, which accounts for a much larger effect on nutrient availability than CO2 fertilisation. Regardless of the scenario used to project future consumption patterns, the net effect of increasing concentrations of atmospheric CO2 will slow progress in decreasing global nutrient deficiencies. 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