The rising level of carbon dioxide in the atmosphere means that crops are becoming less nutritious, and that change could lead to higher rates of malnutrition that predispose people to various diseases.
That conclusion comes from an analysis published Tuesday?in the journal PLOS Medicine, which also examined how the risk could be alleviated. In the end, cutting emissions, and not public health initiatives, may be the best response, according to the paper's authors.
Research has already shown that crops like wheat and rice produce lower levels of essential nutrients when exposed to higher levels of carbon dioxide, thanks to experiments that artificially increased CO2 concentrations in agricultural fields. While plants grew bigger, they also had lower concentrations of?minerals like iron and zinc.
Fewer nutrients in crops means fewer nutrients in food. People who don't get enough of the right nutrients are more likely to get sick. For instance, kids who don't get enough zinc are more likely to contract diseases like malaria, pneumonia and diarrhea.
But how many more people would get sick, and what could be done to keep that from happening?
To answer this question, the researchers took the data we already know about carbon dioxide and crop nutrients and extended it to future CO2 concentrations. Atmospheric carbon dioxide concentrations are expected to rise from 400 parts per million to 550 ppm?by 2050.
Assuming people keep eating the same things, the researchers were able to predict how many more people would become nutrient-deficient as a result of their less nutritious diets. From there, the researchers then inferred changes in disease rates.
The results suggest that rising CO2will cost the world roughly 125 million disability-adjusted life years?- which are roughly equivalent to a year of healthy life - because of higher rates of disease between now and 2050.
Most of the people affected would be in areas prone to malnutrition in Southeast Asia and Africa. Developed regions, such as Europe and North America, are unlikely to be heavily affected.
Next, the researchers simulated what would happen if countries took steps to mitigate the threat, such as reducing CO2 emissions in line with the Paris Agreement on climate, or passing out zinc pills to affected populations.
The researchers found that roughly half of the added disease burden could be avoided if CO2 levels were cut to levels stipulated by the Paris Agreement - 480 ppm. But public health initiatives, like iron distribution or malaria mitigation, would only reduce the problem by a 20 percent.
Diets have changed dramatically?in places like China, where more people are eating meat, a better source of iron than most plant-based foods. Additionally, Myers notes that some crop varieties appear resistant to the CO2-associated decrease in nutrition, and those varieties could provide the foundation for agricultural production in an increasingly CO2-rich atmosphere.
The burden of addressing nutrient deficiency is not likely to fall on the people most responsible for the change. In the end, the study highlights how the habits of affluent countries trickle down to affect the world's poor.
It's the wealthy people in the world who are emitting lots of carbon dioxide, Myers says. "Wealthy consumption patterns are putting the poorest, most vulnerable people in harm's way."