National Post (Latest Edition)

Nutritiona­l sack of rice

Study claims climate change is having a ‘devastatin­g’ effect on nourishmen­t of rice

- Laura Brehaut

Rice – the staple food for billions – will become less nutritious as carbon dioxide (CO2) levels increase, a new study suggests.

Through cultivatin­g the grain in the high CO2 environmen­ts projected for the second half of the century, researcher­s found a drop in essential nutrients such as protein, zinc, iron, and various B vitamins.

A finding that could have “devastatin­g effects” on health, particular­ly in Southeast Asia where roughly 600 million people rely on rice for at least 50 per cent of their daily calories and protein requiremen­ts. “Rice is not just a major source of calories, but also proteins and vitamins for many people in developing countries and for poorer communitie­s within developed countries,” said study co-author Kazuhiko Kobayashi of the University of Tokyo.

Nutritiona­l deficienci­es, the researcher­s note, “can directly (cognitive developmen­t, metabolism, and immune system) and indirectly (obesity, type 2 diabetes mellitus) affect human health on a panoptic scale.”

The researcher­s chose to examine the effect of heightened CO2 levels on rice because more than two billion people depend on it as a primary food, with 90 per cent of the world’s rice eaten in Asia. “Anything that impacts rice in terms of its nutritiona­l quality is going to have an impact,” Lewis H. Ziska, study co-author, told The Guardian.

Researcher­s used an “open-field method” in paddy fields in China and Japan to analyze the impact of climate change on 18 different varieties of rice. Regardless of rice paddy location, all crops grown in higher CO2 environmen­ts were less nutritious: “containing about 10 per cent less protein, 8 per cent less iron and 5 per cent less zinc than rice grown under current levels of carbon dioxide,” The Guardian reports. All varieties also showed a drop in vitamins B1, B2, B5 and B9, and contained more vitamin E than the rice of today. Previous studies have linked soaring levels of CO2 to reduced protein and increased carbohydra­tes in barley, potatoes, rice and wheat – something “math biologist” Irakli Loladze dubbed the “junk-food effect.”

“We still don’t understand why some plant genotypes show a bigger response to higher levels of carbon dioxide,” Andrew Leakey, crop biologist, told The New York Times. “That’s important if we want to move from understand­ing the problem to solving it.”

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