The atmospheric concentration of carbon dioxide (CO₂) has risen dramatically from approximately 280 parts per million (ppm) before industrialization to its current level of 410 ppm, with projections suggesting it may exceed 550 ppm within the next 30 years. This rapid increase in CO₂ levels, alongside other climate change impacts, poses significant risks to food security worldwide, particularly in regions like Sub-Saharan Africa (SSA), which are already vulnerable due to their reliance on staple crops such as maize, rice, and wheat. In SSA, where food systems are fragile and populations are heavily dependent on these crops for daily nutrition, even modest reductions in nutrient quality can have profound implications for public health. As CO₂ levels rise, its impact on crop nutrient content, particularly in key staples, threatens to worsen existing malnutrition and food insecurity in the region.

Elevated atmospheric CO₂ levels have a direct effect on plant growth, especially in C3 plants, which include many staple crops like wheat, rice, and soybeans. These plants benefit from increased CO₂, often leading to higher yields, as observed in free-air CO₂ enrichment (FACE) experiments. However, this potential increase in yield is counterbalanced by a reduction in the nutritional quality of these crops. Studies indicate that rising CO₂ reduces concentrations of essential nutrients, such as protein, zinc, and iron—nutrients critical for human health, especially in regions where grain-based diets predominate. In SSA, where nutrient deficiencies are already widespread, this loss of essential nutrients in staple crops exacerbates both hidden hunger and broader public health challenges.

The physiological response to elevated CO₂ varies between C3 and C4 plants, further complicating the issue. While C3 plants generally show increased growth and yield under elevated CO₂ conditions, C4 crops such as maize are less responsive, as their carbon fixation pathways are already adapted to higher CO₂ environments. This disparity means that while C3 crops may benefit from enhanced yields, the nutritional benefits from these crops will likely diminish. For SSA, where maize is a staple crop, this shift in nutrient dynamics could aggravate existing challenges related to food security and nutrition, particularly as the region's growing population faces an increasing burden from these climate-induced changes.

Long-term projections also highlight the alarming global scale of the issue. Modelling estimates suggest that by 2050, between 122 and 148 million additional people may be at risk of protein deficiency, while 138 to 175 million individuals could face new risks of zinc deficiency due to declining nutrient concentrations in crops. These deficiencies will disproportionately affect developing nations, particularly SSA, where the majority of the population already faces significant nutritional challenges. In SSA, where 80 % of the global cases of nutrient deficiency are concentrated, the rising CO₂ levels will only intensify the region's struggle with malnutrition and food insecurity. Vulnerable groups such as children, pregnant women, and the elderly are particularly at risk, as micronutrient deficiencies can have devastating long-term effects on health, cognitive development, and productivity.