Human nutrition may be threatened in many parts of the world by future elevated atmospheric carbon dioxide (CO₂) concentrations, reports a paper published online this week in Nature Climate Change.

Unless we undertake drastic mitigation efforts, atmospheric CO₂ concentrations are expected to exceed 550 ppm in the next 30-80 years. This increase is expected to reduce the iron, protein and zinc content of many staple crops by 3-17%. These diminished dietary nutrients could lead to negative health outcomes.

Matthew Smith and Samuel Myers examine the impact of elevated CO₂ levels on iron, protein and zinc sufficiency among the populations of 151 countries using an age- and sex-stratified model of availability for 225 different foods.

The authors find that increased CO₂ concentrations could cause an additional 175 million people to be zinc deficient and 122 million to be protein deficient by 2050. Furthermore, 1.4 billion women of childbearing age and children under 5 are currently living in countries with over 20% anaemia prevalence and stand to lose over 4% of their dietary iron intake.

Without a perceptible increase in hunger to motivate efforts to compensate these changes, the prevalence and severity of nutritional deficiency could be increased across the globe. Regions where this will be of particular concern include Africa, South and Southeast Asia, and the Middle East.