Ozone lowers wheat yield by 9%

High levels of ground-level ozone are a threat to crop production and concentrations will likely continue to increase in the coming decades.

By modelling the stomatal uptake of ozone on a global scale, Mills and coauthors found that ozone reduced wheat yield by 9.4% from 2010-2012. This corresponds to 85 Tg of lost grain per year, or losses of $24.2 billion dollars. Losses in developing countries were 50% higher than those in developed countries. This is particularly devastating because (i) developing countries rely largely on home-grown wheat and (ii) the demand for wheat is increasing at twice the rate in developing than developed countries.

Previous studies have simply estimated that the largest effects of ozone will occur in the areas with the highest ozone concentrations. In this study, the authors used a modelling method that accounted for the effects of soil moisture deficit and meteorological factors on the stomatal uptake of ozone. They found that ozone impacts on wheat yield were particularly large in humid rain-fed and irrigated areas where stomatal uptake of ozone is often maximized. This is of particular importance because irrigation will likely expand as countries experience increasing drought due to climate change.

The authors suggest that ozone impacts on yield might be mitigated by both (i) exploiting the genetic variation in ozone resistance in wheat cultivars in breeding programs, and (ii) developing management strategies that protect against ozone damage. Ultimately, though, the largest benefit would accrue from reducing emissions of ozone precursors, with co-benefits for the production of other staple food crops known to be sensitive to ozone as well as for human health, ecosystems and climate.