How climate afects the nutrition of rice
HUMAN-CAUSED greenhouse gas emissions threaten to make rice less nutritious, scientists said in a study released mid-may, raising a worrying possibility about the staple food item of billions of people.
Rice, the scientists found, contains lower levels of key vitamins when grown amid high concentrations of carbon dioxide, the most common of the greenhouse gases driving climate change.
“If we do nothing, there are potentially profound negative impacts on human health,” said Kristie Ebi, a public health researcher at the University of Washington in Seattle and one of the authors of the study, which also involved researchers at institutions in China, Japan, Australia and the US Agriculture Department.
The study, conducted in Japan and China, examined 18 rice varieties in which the plants were subjected to atmospheric carbon dioxide concentrations of 568 to 590 parts per million.
Current concentrations are about 410 parts per million, but they are growing at about 2 parts per million every year — and could reach the study’s levels later this century.
Rice accounts for “approximately 25 per cent of all global calories,” according to the study, which was published in the journal Science Advances. It was led by Chunwu Zhu of the Chinese Academy of Sciences.
The study found that at the high concentrations, the crop’s content of the vitamins B1, B2, B5 and B9 all declined, by as much as 30 per cent for B9 (folate). The research also confirmed previously discovered declines in protein, iron and zinc.
“There have been studies over the past hundred years on the importance of these B vitamins,” Ebi said.
“One that declines with higher CO2 concentrations is folate, whose deficiency in pregnant women can result in children with various birth anomalies. So they are critically important, for our health.”
The study research also suggesting that another major global staple crop, wheat, could see lower yields as the planet warms.
The consequences for wheat are tied to rising temperatures, but with rice, the immediate issue appears to be the growing concentrations of carbon dioxide in the atmosphere.
Plants pull carbon from the air and grow, and they will pull more of it as concentrations rise. The problem is that other aspects of their metabolism may not keep pace, meaning that they would draw in less nutrients from soils as they grow, and proportionately more carbon.
It is the change in this makeup of the plant itself that could, in turn, translate into changes in its nutritional content for those who consume it.
“CO2 is plant food in the sense that it makes plants grow more,” said Lewis Ziska, another study author with the Department of Agriculture.
“But often when plants grow more, it does not necessarily mean you get the same quality of plant.”
The study also fits an increasingly common theme in climate findings, that the poor and disadvantaged globally would be hit hardest by these changes, and would be least able to adjust or diversify their diets in order to obtain nutrients in other ways.
Harvesting rice after devastating floods and landslides submerged paddies across Vietnam last year.