The Heat Is Online

Excess CO2 sucks nutrients out of plants

Rising carbon dioxide levels are making food less nutritious – and it could cause a malnutrition crisis, June 12, 2018


  • High carbon dioxide levels have been shown to reduce rice's nutritional content.

  • Rice is a staple for about two billion people, providing many with over 50% of their daily nutrition.


The huge amount of carbon dioxide we are producing and pumping into the Earth's atmosphere is causing much more damage than previously thought: the rising CO2 levels are responsible not just for global warming but also have a massive impact on the global food system, a new study has shown.


The study, published in the journal Science Advances, shows that an increase in carbon dioxide can significantly reduce the level of micronutrients in certain plants. In the study, researchers studied the effects of the gas on rice — and the results were worrying.


Rice is a staple food source for over two billion people


Rice has been found to contain significantly less protein, iron, zinc and B vitamins after exposure to the level of carbon dioxide our atmosphere is expected to harbour by the end of the century. With several billion people on Earth already suffering from malnutrition, the repercussions of this would be devastating.

"Rice is a staple food source for about two billion people — and the poorest of the population obtain over 50% of their daily nutrition in the form of rice," wrote Lewis Ziska, one of the authors of the study."Anything affecting the nutritional quality of rice will have serious effects."

The researchers point out that previous studies focused mainly on how climate change would change the cultivation of crops. "The quality of the plants and their nutrient content are just as important," says Ziska.

Rice will contain less nutrients and vitamins

In the course of their study, Ziska and his colleagues exposed rice fields planted for research purposes in China and Japan to increased carbon dioxide levels. In doing so, they used values that, according to experts, will appear worldwide in this century as a result of humans.

The majority of the 18 test rice varieties contained significantly less protein, zinc and iron than the rice cultivated today. The researchers found that the content of Vitamins B1, B2, B5 and B9 has decreased dramatically in all varieties. However, the rice contained more Vitamin E.

For people in wealthy countries who are fortunate enough to eat a varied and healthy diet, the problem is initially not so great

"However, in a country like Bangladesh, where rice accounts for about 70% of the daily consumed kilocalories of the population, there are hardly any alternatives to meet their nutrient requirements," wrote Kristie L. Ebi of the University of Washington, who was also involved in the study.

Increased carbon dioxide concentrations change plant compositions

The scientists emphasise that every living being could potentially be affected. The effects on bees and other living organisms, which only have access to a limited number of food sources, have not yet been looked into sufficiently.

Last year another study showed that wheat, another crucial crop, could yield less and less the warmer the planet gets. The negative consequences for wheat are related to rising temperatures, but rice's nutritional quality is directly affected by increasing carbon dioxide levels in the atmosphere.

Plants absorb carbon dioxide — a starting material for photosynthesis — and grow. If the concentration increases, more of it is automatically absorbed by the plants. The problem is that the increased concentration changes the chemical composition of the plant — the nutrient content decreases, while the carbon dioxide content increases.

"Carbon dioxide ensures plants grow strong," wrote Ziska. "That doesn't mean, however, that the quality of the plant is improved."

Other plants could also be affected

There's an urgent need to carry out further studies and to find out why the amount of carbon dioxide in the atmosphere is affecting the nutrient content of plants. It's possible that it's down to the fact that plants grow too quickly with raised levels of carbon dioxide, according to Ziska.

In addition, the scientist emphasises, other crops also need to be investigated. "Many important foods such as wheat and potatoes could also be affected."