WASHINGTON – Rising levels of carbon dioxide in the atmosphere may cut the nutritional quality of some of the world’s most important food crops, researchers have reported after conducting experiments simulating conditions expected by midcentury.
The amounts of two important nutrients, zinc and iron, were found to be lower in wheat, rice, soybeans and peas grown in open-air fields where the scientists created concentrations of carbon dioxide at the level they forecast for Earth by roughly 2050, about 550 parts per million.
They grew 40 varieties of six grains and legumes, also including corn and sorghum, at seven locations in Japan, Australia and the United States.
“This is important because almost 2 billion people globally receive most of these two nutrients [zinc and iron] by eating crops,” said University of Illinois plant biology professor Andrew Leakey, one of the researchers.
The collaboration included researchers from the National Institute for Agro-Environmental Sciences in Ibaraki Prefecture.
The researchers said these findings point to one of the most important health threats linked to climate change.
Dr. Samuel Myers of the Harvard School of Public Health, who led the study, published in the journal Nature, said there already is a significant health problem in parts of the world due to inadequate intake of zinc and iron.
Myers noted that inadequate zinc intake affects the immune system and makes people more vulnerable to premature death from maladies such as malaria, pneumonia and diarrhea. Myers said iron deficiency is linked to increases in maternal mortality, anemia, reductions in IQ and reduced work productivity.
Scientists have sought to gauge the impact of climate change on humankind in the coming decades, including the effects of rising levels of carbon dioxide due to the burning of fossil fuels.
The study found that in wheat grown under elevated levels of carbon dioxide, levels of zinc were about 9 percent lower and iron was 5 percent lower compared to wheat grown under normal conditions. The rice grown with elevated levels of carbon dioxide had 3 percent less zinc content and 5 percent less iron. In wheat and rice, there also was lower protein content.
Nutrients in sorghum and corn remained stable at higher carbon-dioxide levels because these crops use a kind of photosynthesis that concentrates carbon dioxide in their leaves.
The scientists simulated higher levels of carbon dioxide using a system that pumps out, monitors and adjusts carbon dioxide in the air to simulate future conditions.
Except for the level of carbon dioxide, the crops were grown in identical conditions to crops grown outside the ring. The scientists then compared nutrient content in the two sets of crops.
Leakey said more work is needed on why higher levels of carbon dioxide drive down the nutrients.