Plants need carbon dioxide to live, but its effects on them are complicated.

As the level of carbon dioxide in the air continues to rise because of human activity, scientists are trying to understand how the plants we eat are being affected.

According to recent studies, rice, wheat, and other staple crops lose nutrients when exposed to levels of carbon dioxide in the atmosphere expected by 2050.

Samuel Myers, principal research scientist at Harvard’s School of Public Health and director of the Harvard-based Planetary Health Alliance and colleagues have conducted studies in which crops are grown bathed in air that simulates the predicted atmospheric conditions expected both by 2050 and by the end of the 21st century. The studies showed declines in protein, iron, and zinc in wheat, and declines in iron and zinc in soybeans and field peas.

The scientists compared nutrient levels in field crops grown in ambient CO2 levels, about 380-390 parts per milliion (ppm) at the time of the work, with those grown in the elevated CO2 levels expected by 2050. The latter level, 545-585ppm, is expected even if substantial curbs on emissions are put in place by the world’s governments. In order to take account of variable growing conditions, the researchers analysed 41 different strains grown in seven locations on three different continents.

Wheat grown in high CO2 levels had 9% less zinc and 5% less iron, as well as 6% less protein, while rice had 3% less iron, 5% less iron and 8% less protein. Maize saw similar falls while soybeans lost similar levels of zinc and iron but, being a legume not a grass, did not see lower protein.

The precise biological and physiological mechanisms that cause nutrient levels to fall when CO2 levels increase are not yet well understood.

See:

“Major crops lose nutrients when grown in elevated carbon dioxide levels,” Harvard School of Public Health, 19 June 2018

“As Carbon Dioxide Levels Rise, Major Crops Are Losing Nutrients,” Merrit Kennedy, NPR, 19 June 2018

“Climate change making food crops less nutritious, research finds,” Damian Carrington, The Guardian, 7 May 2014

“Increasing CO2 threatens human nutrition,” Samuel S. Myers, Antonella Zanobetti, Itai Kloog, Peter Huybers, Andrew D. B. Leakey, Arnold J. Bloom, Eli Carlisle, Lee H. Dietterich, Glenn Fitzgerald, Toshihiro Hasegawa, N. Michele Holbrook, Randall L. Nels, Michael J. Ottman, Victor Raboy, Hidemitsu Sakai, Karla A. Sartor, Joel Schwartz, Saman Seneweera, Michael Tausz & Yasuhiro Usui, Nature, International Journal of Science, 7 May 2014