Atmospheric carbon dioxide (CO2) levels by 2050 could cause popular crops to lose a great deal of their nutrients, such as zinc and iron.
About two billion people in the world people suffer from zinc and iron deficiencies , causing about 63 million deaths per year, a Harvard School of Public Health news release reported.
"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," Samuel Myers, research scientist in the Department of Environmental Health at HSPH and the study's lead author said in the news release.
Crops grown in greenhouses with elevated CO2 levels were found to be less nutritious than those that were not, but the study showing this was met with skepticism because it used artificial growing conditions.
More recent studies employed free air carbon dioxide enrichment (FACE), which allowed the plants to be grown outdoors.
The research team looked at 41 genotypes of grains and legumes in a site where the CO2 levels were between 546 and 586 parts per million. The grains and legumes were in the C3 and C4 functional groups for carbon fixation.
The team tested the nutrient concentrations in "wheat and rice (C3 grains), maize and sorghum (C4 grains) and soybeans and field peas (C3 legumes)," the news release reported.
The team found a significant decrease in the iron, zinc, and protein levels in C3 grains. The crops grown at the FACE sites saw a 9.3 percent reduction in zinc, a 5.1 percent reduction in iron, and a 6.3 percent reduction in protein. In the legumes at the FACE sites iron and zinc levels were reduced, but not protein.
The researchers estimated about three billion people in the world get 70 percent of their daily zinc and iron from C3 crops. C4 crops are not believed to be as strongly affected by CO2 levels.
"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," Myers said.
