Grains – Championed by crunchy hippie types, loathed by low-carb dieters, beloved by beer drinkers, and depended on by billions in the developing world. Regardless of your opinion of them, there’s no denying the colossal impact the cultivation and consumption of grain has had on the human race. According to researchers at Harvard, life in grain city is about to hit the skids: Due to rising levels of CO2, concentrations of iron in zinc in grains will drop such that the world will lose 63 million life years annually from malnutrition by 2050.

“This study is the first to resolve the question of whether rising CO₂ concentrations – which have been increasing steadily since the Industrial Revolution – threaten human nutrition,” said Samuel Myers, research scientist in the Department of Environmental Health at the Harvard School of Public Health.

The resolution is (obviously) “yes.”

The team was comprehensive in their analysis, and used free air carbon dioxide enrichment testing (FACE) rather than laboratory assessments. They tested nutrient concentrations in edible portions of wheat, rice, maize, sorghum, soybeans and field peas from Japan, Australia, and the U.S. All grain samples were grown in sites with a CO2 range of 546 to 586 parts per million (ppm).

The results found that wheat, rice, soybeans and field peas (grains and legumes that use the C3 carbon fixation) were most affected, registering significant drops in the concentrations of zinc, iron, and protein. Other grains, using the C4 carbon fixation, appeared to be less affected. Myers and his colleagues estimate that 2 billion-3 billion people around the world receive 70 percent or more of their dietary zinc and/or iron from C₃ crops, particularly in the developing world, where deficiency of zinc and iron is already a major health concern.

Based on substantial variability in zinc and iron levels across rice cultivars, the researchers believe that there may be an opportunity to breed strains of rice less affected by the rising levels of CO2.

“Humanity is conducting a global experiment by rapidly altering the environmental conditions on the only habitable planet we know. As this experiment unfolds, there will undoubtedly be many surprises. Finding out that rising CO₂ threatens human nutrition is one such surprise,” said Myers.