Global warming may have ‘devastating’ effects on rice

TAMPA — As carbon dioxide rises due to the burning of fossil fuels, rice will lose some of its protein and vitamin content, putting millions of people at risk of malnutrition, scientists warned on Wednesday.

The change could be particularly dire in Southeast Asia where rice is a major part of the daily diet, said the report in the journal

“We are showing that global warming, climate change and particularly greenhouse gases — carbon dioxide — can have an impact on the nutrient content of plants we eat,” said coauthor Adam Drewnowski, a professor of epidemiology at the University of Washington.

“This can have devastating effects on the rice-consuming countries where about 70% of the calories and most of the nutrients come from rice.”

Protein and vitamin deficiencies can lead to growth-stunting, birth defects, diarrhea, infections and early death.

Countries at most risk include those that consume the most rice and have the lowest gross domestic product (GDP), such as Myanmar, Laos and Cambodia, Mr. Drewnowksi said.

The findings were based on field studies in Japan and China, simulating the amount of CO2 expected in the atmosphere by the second half of this century — 568 to 590 parts per million (ppm). Current levels are just over 400 ppm.

For the experiments, 18 different strains of rice were planted in open fields, surrounded in certain areas by 56- foot wide ( 17- meter) octagons of plastic piping that released extra CO2.

According to study coauthor Kazuhiko Kobayashi, a professor at the University of Tokyo, the experiment is designed to be more accurate than growing in a greenhouse.

“This technique allows us to test the effects of higher carbon dioxide concentrations on plants growing in the same conditions that farmers really will grow them some decades later in this century,” said Mr. Kobayashi.

Researchers found that iron, zinc, protein, and vitamins B1, B2, B5, and B9 — which help the body convert food to energy — were all reduced in the rice grown under higher CO2 conditions.

The reasons for the changes have to do with how higher CO2 affects the plant’s structure and growth, increasing carbohydrate content and reducing protein and minerals, said the study. —