Climate change caused by greenhouse gas emissions is directly affecting the world’s food crops through changes to rainfall, but rising atmospheric carbon dioxide (CO2) levels also change crop quality at the cellular level — with far-reaching consequences for human and animal health.
New research published in Engineering reveals the complex trade-off tied to elevated CO2 concentrations. For most plants — including staples like rice, corn and wheat — higher CO2 levels enhance photosynthesis, boosting growth rates.
But this comes at a cost: elevated CO2 reduces nitrogen, weakening the plant’s ability to produce protein and amino acids and lowering nutritional content.
The report says the global elevated atmospheric CO2 concentration has already decreased the nitrogen content in some crop and woody vegetation species: “…by 14% and 21%, respectively, regardless of added nitrogen fertilizer.
“The mineral nutrient contents in grains of rice and maize were similarly found to decrease under high CO2 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.”
The international team of researchers found wheat grain protein decreased by 7.4% under “elevated” CO2 levels (410ppm, 2019 levels) due to significant reductions in essential amino acids.
Decreases in grain protein, amino acids, and mineral nutrients will have serious consequences, particularly for vulnerable communities, warns Professor Felix Dakora, lead researcher and plant biologist from the Chinese Academy of Agricultural Sciences and the Chemistry Department at Tshwane University of Technology in Pretoria, South Africa.
“The broader implications of reduced amino acid and mineral content in staple crops like rice, maize, and wheat will [include] the inevitable global increase in physiological disorders such as protein-calorie malnutrition and micronutrient deficiency, especially in poorer rural communities of the world,” Dakora says.
“Regions like Africa, where soils are already nutrient-deficient, should expect a doubling in the rate of protein-calorie malnutrition and micronutrient deficiency.”
The problem extends beyond human diets – lower nutrient content in plants impacts the entire food chain.
“Pastures and forage that are low in mineral concentrations, when fed to livestock, will produce meat, milk, or eggs that are also low in nutrients,” Dakora says
“Similarly, grains of cereals and legumes that are poor in nutrients can only lead to nutritionally low-quality foods with consequences for increased rates of diabetes, protein-calorie malnutrition, and micronutrient deficiency.”
To counter rising CO2 levels, the research team highlights the importance of “nature-based solutions” to climate change, such as the Great Green Wall of Africa— a project aiming to restore 100 million hectares of degraded land across the continent. However, more research is needed to fully understand the mechanisms behind these changes in plant biology.
“We need more detailed studies on the effect of climate change on the fundamental biology of crop plant species,” Dakora says.
“We need to revise our research strategies to include the role of soil microbes in plant development under rising atmospheric carbon dioxide. Soil microbes, through the small molecules they produce, can save plant life and improve nutrient availability to crop plants. Genetic modifications can also help”.
More about crops and CO2
The broader consequences of elevated CO2 on plants remain poorly understood, Dr Lewis Ziska told Cosmos. Ziska is an associate professor of Environmental Health Sciences at Columbia University Mailman School of Public Health and was not involved in the research.
“You should think about it not just in terms of nutrition –– how will CO2 affect plant chemistry in ways that will affect plant-based medicines? How will it affect our ‘war on drugs’? How will this change affect the nutritional content of plants that pandas eat? How will the global food chain be affected?
“All life is made possible by plants. We are affecting their chemistry, and we don’t have a clue as to the consequences.”
