Friday, May 30, 2014

More carbon dioxide might reduce crops' nutrients

A new study led by Harvard School of Public Health found that crops that traditionally provide people with much of their dietary zinc and iron will contain less of those nutrients in the coming years, particularly by 2050, due to a predicted rise in atmospheric carbon dioxide. About two billion people deal with zinc and iron deficiencies, "resulting in a loss of 63 million life years annually from malnutrition," Harvard reports. The study was published May 7 in the journal Nature

The researchers studied data from 41 genotypes of grains and legumes from seven locations that used free-air carbon-dioxide enrichment technology, which lets plants grow in fields with increased levels of CO2. Then they tested edible parts of wheat, rice, maize, sorghum, soybeans and field peas. The results showed that "Zinc, iron and protein concentrations in wheat . . . were reduced by 9.3 percent, 5.1 percent and 6.3 percent respectively, compared with what grown at ambient CO2. Zinc and iron were also significantly reduced in legumes; protein was not," Harvard reports.

The researchers estimated that 2 to 3 billion people get at least 70 percent of their dietary zinc and/or iron from C3 crops, such as wheat, rice, soybeans and field peas; this is especially common in the developing world in places where zinc and iron deficiency are already problems. One result that surprised the researchers was that zinc and iron concentrations were not consistent throughout the rice. "That finding suggests that there could be an opportunity to bread reduced sensitivity to the effect of elevated CO2 into crop cultivars in the future," Harvard reports.

Samuel Myers, a research scientist in Harvard's Department of Environmental Health and the study's lead author, said that growing genotypes with less sensitivity to CO2, bio-fortifying crops with iron and zinc, and providing nutritional supplements for people affected by deficiencies, are all potential ways to help. "Humanity is conducting a global experiment by rapidly altering the environmental conditions on the only habitable planet we know. As this experiment unfolds, there will undoubtedly be many surprises," Myers said. "Finding out that rising CO2 threatens human nutrition is one such surprise." (Read more)

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