"These results indicate that the role of rising Carbon dioxide on reducing rice quality may represent a fundamental, but underappreciated, human health effect associated with anthropogenic climate change", the authors, led by Chunwu Zhu of the Chinese Academy of Sciences, wrote in the paper.
According to new research from an global team of scientists, the increasing levels of carbon dioxide in the atmosphere may cause a decrease in the nutritional value of rice.
In the current study, researchers in Japan and China grew and analysed 18 different varieties of rice in fields and found that protein, iron and zinc levels all fell significantly in higher Carbon dioxide environments. This includes a series of vitamins, proteins, zinc, but also iron. Experts interested in the effects of human-caused changes on agriculture crops like rice have typically focused their studies on effects on agricultural production.
Professor Furbank - based at the Australian National University - said researchers should now study and breed varieties that will yield quality - not just quantity in high Carbon dioxide environments.
The findings revealed average declines in vitamins B1, B2, B5 and B9, vitamins essential to helping the body convert food into energy, under a scenario of carbon concentration the scientists expect by the end of this century.
Also, they reported an average 10.3 percent reduction in protein, 8 percent reduction in iron and 5.1 percent reduction in zinc, when compared with rice grown under current carbon concentrations.
The researchers reported no change in levels of Vitamin B6 or calcium, while Vitamin E levels increased for most strains.
It's relatively hard to calculate the exact effect of low rice nutritional value.
The idea that rising carbon dioxide levels are nothing but a positive for global crops is "pure nonsense", Myers said.
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". Scientists are still evaluating exactly how much of a problem these nutrient declines might turn out to be.
Previous studies have linked soaring levels of Carbon dioxide in the atmosphere to reduced protein and increased carbohydrates in crops such as barley, potatoes, rice and wheat - something "math biologist" Irakli Loladze dubbed the "junk-food effect".
The result: an additional 150 million people globally may be at risk of protein deficiency by 2050. The greatest impact and risk of such a result, say the authors, will be to countries consuming the most rice with the lowest GDP.
In the meantime, Ziska hopes to investigate how crop nutrient contents may have already changed in previous decades, in response to historical greenhouse gases emissions.
"Trying to understand those complexities and trying to understand those interactions is one of the things we think is very important", he said.