As carbon dioxide levels rise, grains and legumes will become significantly less nutritious than they are today. Researchers from eight institutions in Australia, Israel, Japan and the United States found that these crops will have significantly reduced zinc and iron concentrations at the elevated levels of atmospheric CO
2 anticipated by around 2050. The researchers reported their findings in the journal
Nature (see
abstract). The researchers looked at multiple varieties of wheat, rice, field peas, soybeans, maize and sorghum grown in fields with atmospheric carbon dioxide levels like those expected in the middle of this century; atmospheric CO
2 concentrations are currently approaching 400 parts per million and are expected to rise to 550 ppm by 2050.
The results showed a significant decrease in the concentrations of zinc, iron, and protein in the grains of
C3 cereals. For example, zinc, iron, and protein concentrations in wheat grains grown at the experimental sites were reduced by 9.3%, 5.1% and 6.3% respectively, compared with wheat grown at ambient CO
2. Zinc and iron were also significantly reduced in legumes; protein was not.
C4 crops appeared to be less affected by higher CO
2, which is consistent with underlying plant physiology, as C4 plants concentrate CO
2 inside the cell for photosynthesis so they might be expected to be less sensitive to extracellular (atmospheric) changes in CO
2 concentration.
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Sources: Harvard School of Public Health and University of Illinois at Urbana-Champaign