A new study highlights a lesser-known but serious consequence of the climate crisis for hundreds of millions of people around the world—major nutritional deficiencies that are likely to hit impoverished populations the hardest, as carbon dioxide emissions seriously affect the quality of food crops.

The study, completed by scientists at the Harvard T.H. Chan School of Public Health and published in the journal Nature Climate Change, found that in just three decades, crops being grown around the world will lose many of their nutritional benefits, thanks to the carbon that’s expected to have entered the atmosphere by 2050.

Samuel S. Myers, a co-author of the study, explained in an op-ed in The Hill:

While crops in some parts of the world are likely to be decimated by the climate crisis, as drought, heatwaves, and extreme weather events become more common, even places where food continues to grow will not be spared from the wide-reaching effects of carbon emissions.

“As concentrations of CO2 approach 550 parts per million by midcentury, hundreds of millions of people are likely to become newly susceptible to chronic deficiencies of protein and zinc. And billions more are likely to suffer from a worsening of their existing nutrient deficiencies,” wrote Myers.

“In the most tragic of ironies, the poorest, who have been least responsible for elevating CO2 levels, will be most vulnerable to these nutrient losses because their diets are less diverse and generally contain lower levels of iron, zinc, and protein.”      —Samuel S. Myers, planetary health scientist

With crops growing on a planet with higher-than-ever concentrations of carbon in its atmosphere, about 175 million people—two percent of the Earth’s population—will by 2050 be eating food that doesn’t provide enough zinc to keep them healthy. 122 million are expected to become protein deficient, and 1.4 million children and women of childbearing age will be at greater risk for iron deficits.