A Nature Letter this week shows that increasing levels of atmospheric CO2 (a greenhouse gas) will cause a decline in the nutritional value of plants important for feeding the globe. The study looked at C3 and C4 plants, which use different biochemical methods to process carbon from CO2. C3 plants were more sensitive to higher CO2 concentrations than C4 plants. C3 plants include many common grains and legumes and more than 95 percent of plant species on earth (rice, wheat, oranges, grapes, potatoes…). C4 plants include corn and sugar cane and represent the second most prevalent form of photosynthetic plants. There is actually a push to make genetically modified rice that will be a C4 plant, which would make it more resistant to increasing CO2 levels (C4 rice).
“Dietary deficiencies of zinc and iron are a substantial global public health problem. An estimated two billion people suffer these deficiencies1, causing a loss of 63 million life-years annually2, 3. Most of these people depend on C3 grains and legumes as their primary dietary source of zinc and iron. Here we report that C3 grains and legumes have lower concentrations of zinc and iron when grown under field conditions at the elevated atmospheric CO2 concentration predicted for the middle of this century. C3 crops other than legumes also have lower concentrations of protein, whereas C4 crops seem to be less affected. Differences between cultivars of a single crop suggest that breeding for decreased sensitivity to atmospheric CO2 concentration could partly address these new challenges to global health.”