People in eighteen countries may lose more than 5% of their dietary protein by 2050, if carbon dioxide levels continue to grow as projected. This is because increased carbon dioxide levels in the atmosphere will lead to a decline in nutritional value of rice, wheat and other staple crops.

While researchers have previously pointed to the link between rising carbon dioxide and falling nutritional content of staple crops, scientists from the Harvard TH Chan School of Public Health in the United States have now quantified the decline. They estimate that roughly 150 million people may be placed at risk of protein deficiency because of elevated levels of carbon dioxide in addition to those who are already not getting enough protein.

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Globally, 76% of the population gets most of their daily protein from plants. The research team set out to estimate their current and future risk of protein deficiency by combining data from experiments in which crops were exposed to high carbon dioxide concentrations with global dietary information from the United Nations and measures of income inequality and demographics.

The study published in the journal Environmental Health Perspectives shows that elevated carbon dioxide concentrations lead to decreased protein of 7.6% in rice, 7.8% in wheat, 14.1% in barley, and 6.4% in potatoes. According to the results, the loss of protein will hit countries in Sub Saharan Africa and South Asia, including India, where millions of people already suffer from protein deficiency and where rice and wheat a large part of daily diets. The researchers found that India may lose 5.3% of protein from a standard diet, possible putting 53 million people at new risk of protein deficiency.

The researchers say that their findings highlight the need for countries that are most at risk to actively monitor their populations’ nutritional needs and for them to curb human-caused carbon dioxide emissions.