Rising carbon dioxide levels are seriously damaging the nutritional value of the world’s most important crops — and it’s only going to get worse, a new study reveals.

The protein content of rice, wheat, barley and potatoes declined between 6 percent and 14 percent under increased CO2 concentrations, putting the world’s most vulnerable populations at greater risk of suffering from severe protein deficiencies, according to the study published in Environmental Health Perspectives.

“These findings are surprising,” Samuel Myers, lead author of the study, told NexusMedia. “If we sat down together 15 years ago and tried to anticipate the human health impacts of anthropogenic CO2 emissions, we would not have predicted that our food would become less nutritious.”

At least 18 countries are at risk of losing over 5 percent of their dietary protein by 2050 if CO2 levels continue to rise. That would place another 150 million people on top of the “hundreds of millions of people who already suffer protein deficiency, whose deficiencies will be exacerbated,” Myers said.

Iron deficiency — already the most widespread nutritional deficiency in the world — is also predicted to become a much larger issue. More than 1 billion women of childbearing age and 354 million children under the age of 5 are estimated to lose 4 percent of their dietary iron from rising CO2 levels, according to a companion study published in GeoHealth. The majority of these at-risk populations live in South Asia and North Africa.

“These findings highlight a major issue of equity,” Myers said. “The people who will be responsible for most of the [increasing] CO2 emissions … are nearly mirror images of the people who will suffer. The wealthier world will emit the CO2 that puts the poorest people with the least diverse diets in harm’s way.”