I wish I had better news for you, but a new study shows that climate change is making our food less healthy. The study, which was recently published in Nature, finds that increased CO2 levels will lesson certain critical nutrients in our food. Heightened levels of atmospheric carbon will make key staple crops wheat, rice, peas, and soybeans less nutritious.
The team, led by Samuel Myers, a research scientist at Harvard’s Department of Environmental Health, grew 40 varieties of six different grains and legumes in plots in the US, Japan, and Australia. They subjected one set to air enriched with CO2 at concentrations ranging from 546 and 586 parts per million—levels expected to be reached in around four decades; the other set got ambient air at today’s CO2 level, which recently crossed the 400 parts per million threshold.
The results: a “significant decrease in the concentrations of zinc, iron, and protein” for wheat and rice, a Harvard press release on the study reports. For legumes like soybeans and peas, protein didn’t change much, but zinc and iron levels dropped. For wheat, the treated crops saw zinc, iron, and protein fall by 9.3 percent, 5.1 percent, and 6.3 percent, respectively. “This study is the first to resolve the question of whether rising CO2 concentrations — which have been increasing steadily since the Industrial Revolution — threaten human nutrition,” said Samuel Myers. According to the Harvard press release, the “reduction in these nutrients represents the most significant health threat ever shown to be associated with climate change.”
Considering that around 2 billion people are already deficient in zinc and iron, causing an estimated loss of 63 million life-years annually, these findings are a major concern. Symptoms of zinc deficiency include stunted growth, appetite loss, impaired immune function, hair loss, diarrhea, delayed sexual maturation, impotence, hypogonadism (for males), and eye and skin lesions; while iron deficiency brings on fatigue, shortness of breath, dizziness, and headache. Myers and his colleagues estimate that currently 2 billion–3 billion people around the world receive 70 percent or more of their dietary zinc and/or iron from these crops, particularly in the developing world, where deficiency of zinc and iron is already a major health concern.
Stephen Long, an agronomist at the University of Illinois at Urbana-Champaign who did not participate in the study, reminds us that “Rising global CO2 increases yield and decreases water use by crops, and this is often presented as one positive of atmospheric change, but the Nature study’s “significant” finding suggests that higher-CO2 environments will mean less nutritional crops, so that “increased quantity is at the expense of quality.” CO2 enrichment experiments at Long’s university have also shown that rising CO2 levels lower crops’ resistance to pests. By exposing the plants to levels of CO2 similar to those used in the Harvard-led study, says Long, crop damage from three major crop pests doubled. Naturally this raises the concern that even more chemicals will need to be used on our crops in the future as CO2 levels continue to rise.
Myers and his colleagues suggest there should be a global effort to develop new breeds of wheat, rice, peas and soybeans that show resistance to higher CO2 levels. While the various cultivars of wheat, peas and soybeans in their study all suffered similar nutrient losses in response to higher CO2, rice offered a ray of hope: Its cultivars varied wildly in their response. “So there may be some basis for breeding rice and potentially other strains that are less sensitive to this effect,” says Myers. Here’s to hoping this doesn’t turn into an excuse to develop more GMOs. Perhaps we should focus on lowering that CO2 instead.
“Humanity is conducting a global experiment by rapidly altering the environmental conditions on the only habitable planet we know. As this experiment unfolds, there will undoubtedly be many surprises. Finding out that rising CO2 threatens human nutrition is one such surprise,” Myers said.