Computer models suggest elevated CO2 in Earth’s atmosphere could adversely affect global health by reducing nutrient levels in crops, Harvard University researchers report (Nat. Clim. Change 2018, DOI: 10.1038/s41558-018-0253-3). Prior field studies established that elevated CO2 makes certain crop nutrient levels drop, by a mechanism that’s still unknown. Given current emission trajectories, by 2050 the effect could make an additional 175 million people zinc deficient and 122 million protein deficient, the researchers say. Under the same scenario, 1.4 billion children under age five and women of childbearing age will live in high-risk areas for iron deficiency. Lack of zinc, protein, or iron can cause developmental and immune problems, as well as anemia and infant/maternal mortality. When the researchers assigned and added up risk scores for those three nutrients, they found that countries relying on crops such as wheat and rice would be the hardest-hit areas (map shown). The researchers hope their study raises awareness about how rising CO2 could cause harmful health outcomes, and they encourage countries at risk to improve the diversity and quality of their residents’ diet.