Among crop species, rice is the primary food source for more than 2 billion people, and previous studies have found that projected increases in atmospheric CO2 can result in an ionomic imbalance for most plant species whereby carbon increases disproportionally to soil-based nutrients.
This imbalance, in turn, may have significant consequences for human nutrition including protein and micronutrients.
Therefore, researchers from China and Japan conducted used multiyear and multilocation experiments for 18 genetically diverse rice lines, including Japonica, Indica, and hybrids currently grown throughout Asia.
When grown under field conditions at anticipated CO2 levels, protein content releative to CO2 declined by 10.3% for all rice types.
Significant reductions in iron and zinc were also observed, of 8% and 5.1% respectively.
“As of 2013, approximately 600 million individuals, primarily in South East Asia — the countries of Bangladesh, Cambodia, Indonesia, Lao People’s Democratic Republic, Madagascar, Myanmar, and Vietnam — consume more than 50% of their per capita dietary energy and/or protein directly from rice,”wrote the researchers.
“The data shown here provide the first integrated assessment of [CO2]-induced changes in nutritional quality (protein, minerals, and vitamins) for many of the most widely grown rice lines; as such, they indicate that, for key dietary parameters, the [CO2] likely to occur this century will add to nutritional deficits for a large segment of the global population.”
While the researchers added it was difficult to provide exact estimates of the nutritional deficits and associated health consequences likely to incur among rice-dependent populations, they maintained “CO2-induced reductions in these qualities and associated risks of undernutrition or malnutrition are likely to transcend the entire food chain, from harvest to consumption, especially for the poorest people within a country or region.”
In terms of solutions, the researchers argued that cultivar selection, either through traditional breeding or genetic modification, could provide nutritionally superior rice with additional CO2.
They also said fortification should be further assessed, and that consumers needed to be made aware of the situation that was likely to unfold over the coming decades.
“Carbon dioxide (CO2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries”
Authors: Chunwu Zhu, et al