Exploring the Impacts of Elevated CO2 on Food Security: Nutrient Assimilation, Plant Growth, and Crop Quality

Despite its negative impacts on plant functioning, climate change benefits plants at the cellular level. For example, the stimulation of C3 photosynthesis by elevated CO 2 can increase N 2 fixation by 73% and grain yield by 10%–11%. The global elevated atmospheric CO 2 concentration has already decreased the nitrogen content in C3 crop species and C3 woody vegetation by 14% and 21%, respectively, regardless of added nitrogen fertilizer . 15 N-feeding experiments have shown that, after 19 h under elevated CO 2 , the 15 N concentration in the stems, roots plus rhizomes, and whole plants of Scirpus olneyi ( S . olneyi ) decreased by 51%, 63%, and 74%, respectively. Moreover, S. olneyi showed reduced NH 4 + assimilation under elevated CO 2 , which decreased the amino acid contents in the stems by 25.6% for glycine and 65.0% for serine , and that in the roots plus rhizomes by 2% for gamma-aminobutyric acid (GABA) and 80% for glutamate. Wheat grain protein has also been found to decrease by 7.4% under elevated CO 2 due to reductions in threonine , valine , iso-leucine, leucine , and phenylalanine . The mineral nutrient contents in grains of rice and maize were similarly found to decrease under high CO 2 by 1.0% and 7.1% for phosphorus, 7.8% and 2.1% for sulfur, 5.2% and 5.8% for iron, 3.3% and 5.2% for zinc, 10.6% and 9.9% for copper, and 7.5% and 4.2% for manganese, respectively. In general, mineral concentrations in C3 plants are predicted to decrease by 8% under elevated CO 2 , while total non-structural carbohydrates (mainly starch and sugars) are expected to increase. These decreases in grain protein, amino acids, and mineral nutrients could double the incidence of global protein-calorie malnutrition and micronutrient deficiency—especially in Africa, where agricultural soils are inherently low in nutrient elements. Additionally, the increase in total non-structural carbohydrates (mainly starch and sugars) in cereal crops could elevate diabetes incidence due to heavy reliance on starchy diets. The negative effects of elevated CO 2 on rice, maize, and wheat—the world’s three major staple crops—suggest an increase in global food insecurity with rising atmospheric CO 2 concentration.