A new study published on 27 August in Nature Climate Change has shown that elevated carbon dioxide (CO2) levels in the atmosphere are affecting the nutrient content of staple crops, such as rice, wheat, and maize, in the 151 countries that were assessed (1). Humans obtain the majority of required nutrients ― including dietary protein, iron, and zinc ― from plants. However, researchers from Harvard T.H. Chan School of Public Health have now shown that higher levels of CO2 in the atmosphere are resulting in less nutritious crop yields.
The study was built upon previous analyses of CO2-related nutritional deficiencies but this time, to improve their previous estimates on the impact of CO2, the researchers looked at a larger number of foods across more countries. They used detailed age- and sex-specific food supply datasets and defined a unified set of assumptions across nutrients in 225 different foods in order to gain more precise estimates of the individual demographic impacts.
Based on the analysis, it is estimated that concentrations of protein, iron, and zinc of certain crops would be 3 to 17% lower when crops are grown in environments at which CO2 concentrations are 550 parts per million (ppm) compared to crops grown under current atmospheric conditions, in which CO2 levels are just above 400 ppm. The 400 ppm level was surpassed in 2016 and current climate change models are predicting concentrations of nearly 940 ppm by the end of the century.
This is of particular significance since CO2 concentrations are expected to reach 550 ppm by 2050 due to human influence ― how we heat our homes, what we eat, how we move around, and what we purchase ― and this is having an even larger impact on health owing to the reduction in nutrients in important crops. According to the paper, elevated CO2 levels could potentially cause an additional 175 million people to become zinc deficient and 122 million people to become protein deficient by 2050.
Furthermore, two billion people currently live with nutritional deficiencies and would likely see their conditions worsen as a result of less nutritious crops. The findings also suggest that the 1.4 billion women of childbearing age and children under 5 in countries with greater than a 20% incidence of anaemia would lose more than 4% of their dietary iron. The study also suggests the populations that will be most significantly affected in the future are India, followed by South Asia, Southeast Asia, Africa, and the Middle East.
The study highlights the sheer extent of climate change effects on the environment and how rising CO2 levels will impact aspects of human, in particular, there is a growing global health burden associated with CO2-related nutritional shifts in crops.
(1) Smith, M.R. and Myers, S.S. Impact of anthropogenic CO2 emissions on global human nutrition. Nature Climate Change (2018) DOI: 10.1038/s41558-018-0253-3