Food Quality Declining Thanks To Rising Levels Of Atmospheric Carbon Dioxide
April 7, 2014

Increased CO2 Levels Will Cause Food Quality To Decline

redOrbit Staff & Wire Reports - Your Universe Online

Research published Sunday in the journal Nature Climate Change has demonstrated for the first time that the increasing amount of carbon dioxide in the Earth’s atmosphere could have an adverse effect on the planet’s food supply.

Professor Arnold J. Bloom of the University of California-Davis Department of Plant Sciences and his colleagues conducted a wheat field test study that determined that the nutritional quality of food-producing crops could suffer as climate change grows more intense.

“Food quality is declining under the rising levels of atmospheric carbon dioxide that we are experiencing,” Bloom said in a statement. “Several explanations for this decline have been put forward, but this is the first study to demonstrate that elevated carbon dioxide inhibits the conversion of nitrate into protein in a field-grown crop.”

The reason for this is because of the key role that that nitrogen assimilation plays in a plant’s growth and productivity. Nitrogen processing is especially vital to food crops, since they use the elements to produce the proteins that play such an important role in human nutrition.

While prior laboratory studies had already discovered that elevated atmospheric CO2 levels would inhibit nitrate assimilation in the leaves of grain and non-legume plants, this new study is the first to verify that this phenomenon also inhibits nitrogen processing in field-grown plants, according to the authors.

In order to observe how wheat, which accounts for roughly 25 percent of all protein in the global human diet, responds to various levels of atmospheric carbon dioxide, Bloom and his associates examined samples of the crop that had been grown in 1996 and 1997 at the Maricopa Agricultural Center in Arizona.

CO2-enriched air had been released into the fields at that time, which created an elevated level of the greenhouse gas similar to what is expected to be the norm within the next few decades. They also had control crops in which the wheat was grown in normal air that had not been treated with additional carbon dioxide.

“Leaf material harvested from the various wheat tests plots was immediately placed on ice, and then was oven dried and stored in vacuum-sealed containers to minimize changes over time in various nitrogen compounds,” according to Pat Bailey of UC Davis' News Service. “A fast-forward through more than a decade found Bloom and the current research team able to conduct chemical analyses that were not available at the time the experimental wheat plants were harvested.”

In their study, Bloom’s team documented that the three different nitrate assimilation measurements they had taken demonstrated that the elevated CO2 levels in the air had inhibited nitrate assimilation into protein in the field-grown wheat. He said that the findings were consistent with previous laboratory research.

According to the professor, there are “several physiological mechanisms responsible for carbon dioxide's inhibition of nitrate assimilation in leaves.” Furthermore, he said that other studies have shown that wheat, rice and barley grains experience an approximately eight percent decline in protein concentrations when exposed to higher CO2 levels.

“When this decline is factored into the respective portion of dietary protein that humans derive from these various crops, it becomes clear that the overall amount of protein available for human consumption may drop by about 3 percent as atmospheric carbon dioxide reaches the levels anticipated to occur during the next few decades,” said Bloom, whose research was funded by the National Science Foundation and the USDA’s National Institute of Food and Agriculture.

This decline in food quality could be at least partially compensated for with heavy nitrogen fertilization, although the researchers point out that this would have a negative impact on the crops as well. It would increase agricultural costs and would lead to an increased amount of nitrate leaking into groundwater and higher emissions of another greenhouse gas, nitrous oxide, Bloom noted.