Crop

Changing climate could worsen foods’ nutrition

Arizona wheat field
CROP FUTURES Experiments using circles of white pipes blowing extra carbon dioxide over crops suggest that certain nutrients may dwindle in crops grown in a carbon-enhanced future atmosphere. Here, researchers in Arizona measure the growth of wheat.

A dinner plate piled high with food from plants might not deliver the same nutrition toward the end of this century as it does today. Climate change could shrink the mineral and protein content of wheat, rice and other staple crops, mounting evidence suggests.

Selenium, a trace element essential for human health, already falls short in diets of one in seven people worldwide. Studies link low selenium with such troubles as weak immune systems and cognitive decline. And in severely selenium-starved spots in China, children’s bones don’t grow to normal size or shape. This vital element could become sparser in soils of major agricultural regions as the climate changes, an international research group announced online February 21 in Proceedings of the National Academy of Sciences.

Likewise, zinc and iron deficiencies could grow as micronutrients dwindle in major crops worldwide, Harvard University colleagues Samuel Myers and Peter Huybers and collaborators warned in a paper published online January 6 in the Annual Review of Public Health. Futuristic field experiments on wheat and other major crops predict that more people will slip into nutritional deficits late in this century because of dips in protein content, Myers reported February 16 at the Climate and Health Meeting held in Atlanta.

“If we’d sat down 10 years ago and tried to think what the effects of anthropogenic carbon dioxide emissions might be on human health, none of us would have anticipated that one effect would be to make our food less nutritious,” Myers said. “But we can’t fundamentally disrupt and reconfigure most of the natural systems around our planet without encountering unintended consequences.”

Figuring out those unintended nutrient consequences isn’t easy. For selenium, scientists have only a rough idea of the element’s global movements. It’s unclear what proportions erode out of rocks or waft onto land from sea, says biogeochemist Lenny Winkel of ETH Zurich and the Swiss aquatic research group Eawag in Dübendorf. She was the principal investigator for the selenium in soils project in the new Proceedings paper. As far as she knows, it presents the first global look at selenium concentrations in soils and what basic factors influence what’s there. This scale, she says, was “a bit bold.”

Starting with more than 33,000 data points from other sources, Winkel and colleagues pieced together a map of selenium concentrations in soils across much of the globe. Climate popped out as one of the more important predictors of selenium content in soil, a link that hadn’t shown up in small studies. Places where climate turns land arid generally have lower selenium, but soil character matters, too. Places with high organic carbon, as in a woodland rich with fallen leaves, as well as places with abundant clay, tend to do better at retaining selenium.

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Selenium slump

Soil concentrations of the element selenium, essential for human life, could change by the end of the 21st century, according to computer simulations based on an intermediate scenario for climate change (a scenario that the Intergovernmental Panel on Climate Change labels RCP6.0). The analysis identified what influences soil selenium now — including precipitation and concentrations of organic carbon in soil — and predicted future concentrations based on those influences.

G.D. Jones et al/PNAS 2017

By the end of the century, about two-thirds of heavily cultivated agricultural land would probably lose selenium under an intermediate scenario of climate change, Winkel and colleagues conclude. With a projected average end-century warming of 2.2 degrees Celsius compared with 1986 to 2005, selenium drops in breadbasket regions in the study by an average of 8.7 percent. Only 19 percent of croplands seem likely to gain selenium.

The new map “is worrisome,” says plant physiologist Philip White of the James Hutton Institute in Invergowrie, Scotland. White, who studies agricultural plants,…

How to grow toxin-free corn

transgenic corn infected with fungus
GRAIN TRAINING Genetically altered corn infected with Aspergillus fungus (shown) may be able to prevent the fungus from releasing carcinogenic toxins.

Corn genetically engineered to make ninjalike molecules can launch an attack on invading fungi, stopping the production of carcinogenic toxins.

These specialized RNA molecules lie in wait until they detect Aspergillus, a mold that can turn grains and beans into health hazards. Then the molecules pounce, stopping the mold from producing a key protein responsible for making aflatoxins, researchers report March 10 in Science Advances. With aflatoxins and other fungal toxins affecting up to 25 percent of crops worldwide, the finding could help boost global food safety, the researchers conclude.

“If there’s no protein, no toxin,” says study coauthor Monica Schmidt, a plant geneticist at the University of Arizona in Tucson.

Schmidt and colleagues used a technique called RNA interference, which takes advantage of a natural defense mechanism organisms use to protect against viruses. The researchers modified corn to make it produce short pieces of RNA that match up to sections of an RNA in the fungus made from the aflC gene. That gene encodes the first step of a biochemical pathway that the fungus uses to make the toxins. When the corn’s modified RNAs match up with those of the fungus, that triggers Aspergillus to chop up its own RNA, preventing a key protein, and thus the toxin, from being made.

Then, the team infected both…