High levels of carbon dioxide could be making rice less nutritious

Rice is the culinary foundation for much of the world and provides 25 percent of the total calories consumed globally. According to research in Science Advances Critical, nutrients found in rice which include protein, B vitamins, iron and zinc are poised to decline. “It is the primary food available for the poorest people in the world, particularly for those in Asia,” said Lewis Ziska, co-author of the new study.

Ziska and his colleagues studied 18 rice strains grown around the world using a technique called Free-Air Carbon dioxide Enrichment (FACE). The rice was grown at sites in China and Japan using an open-field method within standard rice fields. Plants were subjected to atmospheric carbon dioxide concentrations of 568 to 590 parts per million. Current concentrations are 410 parts per million – and growing each year at about 2 parts per million.

After harvesting the rice, researchers found an average of 10.3 percent reduction in protein across all the tested varieties and one cultivar showed a 20 percent drop in protein. Iron content fell an average of 8 percent, while the average decline in zinc was 5.1 percent, with some strains experiencing a 15 percent fall. Vitamin B1, B2, B5 and B9 concentrations also fell as CO2 levels rose.  

The research aligns with a common theme in climate findings, which is that poor and marginalized communities around the world would be most affected by the reduction of nutrients. It also shows that these individuals would find it difficult to adjust and diversify their diets to obtain nutrients that they would be lacking. Approximately 600 million people in countries including Bangladesh, Cambodia and Indonesia get more than half of their daily calories and protein directly from rice.

The finding has serious public health implications, especially as CO2 emissions are projected to increase in the coming decades. This may push the international community to adopt more effective initiatives to lower our global production of CO2.

However, not all varieties of rice responded the same way. Future research may examine the possibility of finding varieties of rice that can remain nutritious despite the change in the atmosphere – a project that is critical to maintaining standards of global public health.

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