Dietary Transitions Can Overcome the Nutritional Threat of Increasing CO2

Abstract:

Elevated atmospheric CO₂ (eCO₂) threatens global food security by affecting the nutritional quality of food crops, especially C3 plants (e.g., wheat and rice). At the same time, historical and projected dietary shifts towards higher nutrient intake could buffer these impacts. However, whether increases in nutrient availability from dietary shifts could outweigh nutrient losses from rising CO₂ while also addressing persistent undernourishment remains unclear. To evaluate if dietary changes can mitigate the effect of eCO₂, we first estimate historical changes in the supply of protein, iron, and zinc for 172 countries and 76 food items, finding that 19.5%, 23.6%, and 9.5% of the world’s population currently fall below the Recommended Dietary Allowance (RDA) for protein, iron, and zinc, respectively. Although the historical nutrient availability of many countries is higher than current levels, we find that approximately 60% of the world’s population would not be able to offset the effects of eCO₂ by reverting to past diets. We then examine changes in nutrient supply under income-based, planetary health (i.e., EAT-Lancet), and healthy (i.e., Mediterranean, vegetarian) dietary projections to 2050 and compare these to the effects of eCO₂. The fraction of people experiencing undernutrition decreases by 10.8%, 15.3%, and 18.9% (2.1 p.p., 3.6 p.p., and 1.8 p.p.), when moving from current to 2050 income-based diet; when also considering the effect of eCO₂, this fraction increases to 18.9%, 8.9%, and 22.2% for protein, iron, and zinc, respectively. Compared with other healthy diets (i.e., Mediterranean, vegetarian), the EAT-Lancet diet would experience smaller nutrition losses due to eCO₂ at the same calorie intake level of 2500 kcal/capita/day. Together these findings demonstrate that dietary transitions will likely play a larger role in improving nutritional outcomes but that future diets may still be vulnerable to the effects of eCO₂ depending on their composition.