The world already has a hard time properly allocating crucial nutrients to its 7.125 billion residents — and a new study published in The Lancet Wednesday suggests that global warming is only going to increase that challenge.
According to the World Health Organization, zinc deficiency currently impacts a little more than thirty percent of humans across the globe. An important mineral found in shellfish, red meat, seeds, legumes, and cereal grains, zinc helps the immune system function properly, aids in the creation of proteins and DNA, and plays a crucial role in development and growth in infants. A lack of zinc in the diet can cause diarrhea, exacerbate malaria and pneumonia, and lead to death. In fact, zinc deficiency is estimated to cause more than 450,000 deaths in children under the age of five each year, accounting for 4.4 percent of global childhood deaths.
New research, led by Samuel Myers, a senior research scientist at Harvard University’s T.H. Chan School of Public Health, suggests that increasing levels of carbon dioxide in the earth’s atmosphere will only make global zinc deficiency worse, putting some 138 million people at risk of malnutrition by the year 2050.
The researchers arrived at that conclusion through a meta-analysis of a variety of different data sets. They first looked at zinc consumption in 188 countries under ambient CO2 concentrations, based on data from the U.N.’s Food and Agriculture Organization. Then, they looked at data from previous experiments that grew crops under varying CO2 concentrations to see how their nutrient makeup was impacted — those experiments showed reduced levels of key nutrients, including zinc, when crops like wheat, barley, rice, and soy are grown in high concentrations of CO2.
The researchers then looked at how much zinc humans need to be healthy, and what sources people in different countries tend to get their zinc from. Finally, they compared that information — how many people need a threshold amount of zinc from various crops — to how those crops might look grown under higher concentrations of carbon dioxide. In the end, they found that some 138 million people were likely to be at risk of zinc deficiency by 2050, with Africa and South Asia bearing the brunt of the changes (nearly 48 million of the estimated malnourished would live in India alone).
It’s known that the consequences associated with climate change will most heavily impact the poor, but this study widens those consequences beyond sea-level rise and natural disaster response. When climate change impacts the nutrients of crops, it’s the world’s poor that are most likely to become malnourished. Those in wealthy countries can supplement their nutrients with animal products, but those in poor countries are often more dependent on plant-based nutrients.
“It’s very clear that there’s this weird inversion where the wealthiest people are putting the most carbon dioxide in the atmosphere, and the poorest people are experiencing the most vulnerability to this effect,” Myers told the Washington Post.
In their analysis, Myers and his colleagues didn’t account for changing global diets in the face of climate change. It’s possible, the study allows, that as global CO2 concentrations increase, global diets could shift in a way that exacerbates nutrient deficiency, as agricultural production struggles to keep up with population growth, water scarcity, and land degradation.
The study also didn’t take into account population growth, meaning that the 138 million people that Myers and the other researchers estimate could face nutrition shortages is almost certainly an underestimate.
“We all know that there are going to be something like another two to three billion people sharing the planet with us by 2050,” Myers told the Washington Post. “And so if you just scale the effect, it would be much higher numbers [of affected people].”