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Rising CO2 levels may cut nutrient levels in crops, study finds

Wheat and rice were lower in zinc, iron and protein at higher levels of CO2

Rising levels of carbon dioxide in the atmosphere may cut the nutritional quality of some of the world’s most important food crops, researchers reported May 7 after conducting experiments simulating conditions expected by mid-century.

The amounts of two important nutrients, zinc and iron, were found to be lower in wheat, rice, soybeans and field peas grown in open-air fields where the scientists created CO2 concentrations at the level they forecast for Earth by roughly 2050, about 550 parts per million.

They grew 40 varieties of six different grains and legumes, also including corn and sorghum, at seven locations on three continents, in Japan, Australia and the United States.

“This is important because almost two 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 researchers said these findings point to one of the most important health threats shown to be 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 public 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 like malaria, pneumonia and diarrhea. Myers said iron deficiency is linked to increases in maternal mortality, anemia, reductions in IQ and reduced work productivity.

Earth’s atmospheric CO2 concentration currently is about 400 parts per million and continues to rise.

The study found that in wheat grown under elevated CO2 conditions there were about nine per cent lower levels of zinc and five per cent lower levels of iron compared to wheat grown under normal conditions. The rice grown with elevated CO2 levels had three per cent less zinc content and five per cent less iron.

In wheat and rice, there also was lower protein content at the elevated carbon dioxide levels, the researchers said.

Leakey said rice, wheat and soybeans made more sugars through photosynthesis at the elevated CO2 levels and produced about 15 per cent more seeds but had decreases in zinc and iron content.

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