The study provides a detailed overview of the impacts of increased atmospheric carbon dioxide (CO2) concentrations on food security, focusing on nutrient assimilation, plant growth and crop quality. The authors emphasize that while elevated CO2 levels may have some positive effects on plants at the cellular level, such as stimulating C3 plant photosynthesis, which can lead to increases in nitrogen (N2) fixation by up to 73 % and cereal yields by 10–11 %, there are also significant negative consequences for food quality and nutrition.

Global increases in atmospheric CO2 concentrations have already reduced nitrogen content in C3 crops and woody plants by 14 % and 21 %, respectively. in the above order, regardless of the added nitrogen fertilizers. Experiments with 15N isotope labeling showed that after 19 hours under elevated CO2, the concentration of 15N in different parts of the Scirpus olneyi (S. olneyi) plant decreased significantly. In addition, S. olneyi showed reduced assimilation of ammonium ion (NH4+), which led to a decrease in amino acid content in stems (glycine by 25.6 %, serine by 65.0 %) and roots (GABA by 2 %, glutamate by 80 %). Protein content in wheat (by 7.4 %) and mineral nutrient content in rice and maize grains (phosphorus, sulfur, iron, zinc, copper, manganese) also decreased. Overall, mineral concentrations in C3 plants are predicted to decrease by 8 % under elevated CO2, while the content of non-structural carbohydrates (starch and sugars) will increase. These changes may double the incidence of global protein-energy malnutrition and micronutrient deficiencies, especially in Africa. The increase in carbohydrates could contribute to the increase in diabetes. The negative effects on rice, maize and wheat point to increasing global food insecurity with increasing CO2 concentration.

Despite the negative impacts on quality, increased CO2 stimulates growth and photosynthetic activity of C3 plantsMany studies have confirmed increase in dry matter production and grain yield in C3 plants under elevated CO2. For example, spring wheat biomass and grain yield increased by approximately 11 % and 10.4 % under elevated CO2 conditions, respectively. However, the combination of elevated CO2 and high temperature can have negative effects on wheat and rice yields.

The document also deals with the effect of increased CO2 on microbial nitrogen fixation. Elevated CO2 has been found to stimulate nitrogenase activity in associative diazotrophs in the roots of C3 plants such as S. olneyi and increase 15N incorporation. Similarly, it has been found that non-symbiotic nitrogen fixation in soil without plants increases under elevated CO2. In the case of legume CO2 enrichment has been shown to increase nitrogen fixation and stimulate photosynthetic efficiency. Legumes could have an advantage in a changing climate due to their ability alleviate photosynthetic acclimation.

The report discusses in detail reduced intake and assimilation of nitrates (NO3-) and ammonium ions (NH4+) in C3 plants under elevated CO2, leading to a decrease in nitrogen content in tissues. It has been found that elevated CO2 inhibition of nitrate assimilation, a decrease in the activity of nitrate reductase and nitrite reductase, inhibition of leaf protein formation and a decrease in the levels of NO3-, NH4+ and amino acids. At the level of nutrient intake, a connection was found between the absorption of mineral nutrients and transpiration. Reduced transpiration due to reduced stomatal conductance under elevated CO2 may affect nutrient uptake. Studies have shown that inhibition of 15N assimilation in S. olneyi under elevated CO2 occurs at the initial step of mineral nitrogen conversion to amino acids via the GS-GOGAT pathway. Reduced 15N concentration in tissues resulted in a significant decrease in amino acid levels.

The report also highlights changes in mineral nutrient concentrations (ionomics) under elevated CO2. A decrease in the content of macronutrients (sodium, calcium, magnesium, phosphorus, sulfur) and micronutrients (iron, zinc, manganese) in wheat, rice and maize grains has been found. These changes have negative consequences for human nutrition and healthThe mechanisms of mineral depletion are not fully understood, but are thought to be related to reduced transpiration and possible by regulating ion transporters in the roots.

The authors propose exploiting the positive effects of high CO2 for plant growth to reduce global warming and restore the health of the planet. They propose breeding crops with naturally higher nutrient content (biofortification) a mandatory tree planting, especially economically important N2-fixing trees, shrubs and grasses. Promoting consumption legumes could reduce methane production from livestock. The project The Great Green Wall of Africa is an example of an initiative that uses increased CO2 to promote vegetation growth and carbon sequestration.

At the end of the study, it points out paradoxical impact of increased CO2 to nitrogen, which stimulates nitrogen fixation but at the same time reduces its uptake and assimilation. It is emphasized risk to global food security and nutrition due to a reduction in protein and mineral nutrient content in major cereals, which could lead to increased malnutrition and micronutrient deficiencies. Further research into the physiological, molecular, metabolic and ecological responses of C3 plants to elevated CO2, as well as the use of AI in breeding, is needed to address these issues. Spring

The study is published in Engineering .

Glossary of key terms

• Nutrient assimilation: The process by which plants take up and incorporate inorganic nutrients (such as nitrogen and minerals) into organic compounds needed for growth and development.
• Diazotrophy: The ability of microorganisms to fix atmospheric nitrogen (N2) and convert it into ammonia (NH3), a form of nitrogen available to plants.
• Nitrogen fixation (N2 fixation): The conversion of atmospheric nitrogen into nitrogen compounds that can be used by plants and other organisms. It can be biological (by microorganisms) or industrial (Haber-Bosch process).
• Photosynthesis: The process by which plants use light energy to convert carbon dioxide and water into organic compounds (sugars) and oxygen.
• GS-GOGAT: The main metabolic pathway in plants for ammonia assimilation, involving the enzymes glutamine synthetase (GS) and glutamate synthase (GOGAT).
• Ionomics: The study of the overall ionic composition of cells, tissues, or entire organisms, including mineral nutrients and trace elements.
• Non-structural carbohydrates: Storage carbohydrates in plants, mainly starch and soluble sugars, which serve as a source of energy.
• Nutritional quality: The content and availability of essential nutrients (such as protein, vitamins, and minerals) in foods.
• Ventilatory conductivity: The degree to which stomata on the leaf surface are open, which affects gas exchange (CO2 and O2) and water transpiration.
• C3 plants: Plants that form a three-carbon compound (3-phosphoglycerate) as the first product of photosynthesis. Examples include rice, wheat, and soybeans.
• C4 plants: Plants that have a specialized mechanism for concentrating CO2 around the enzyme Rubisco and form a four-carbon compound as the first product of photosynthesis include corn and sorghum.
• Rhizobiomes: Soil bacteria that form a symbiotic relationship with the roots of legumes, in which they fix atmospheric nitrogen.
• Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase): A key enzyme in the process of photosynthesis that catalyzes the fixation of carbon dioxide.
• Transpiration: The process of evaporation of water from plants, mainly through stomata on leaves.