The introduction of high-performing crop cultivars and crop/soil water management practices that increase the stomatal uptake of carbon dioxide and photosynthesis will be instrumental in realizing the United Nations Sustainable Development Goal (SDG) of achieving food security. To date, however, global assessments of how to increase crop yield have failed to consider the negative effects of tropospheric ozone, a gaseous pollutant that enters the leaf stomatal pores of plants along with carbon dioxide, and is increasing in concentration globally, particularly in rapidly developing countries. Earlier studies have simply estimated that the largest effects are in the areas with the highest ozone concentrations.

Photo of crop irrigation

Humid regions of the globe where Irrigation of crops is used to mitigate the effects of climate change are at greater risk of ozone pollution damage. Image source: Pixabay https://pixabay.com/en/irrigation-agriculture-farming-403371/

The research team used a modelling method that accounts for the effects of soil moisture deficit and meteorological factors on the stomatal uptake of ozone, and show for the first time that ozone impacts on wheat yield are particularly large in humid rain-fed and irrigated areas of major wheat-producing countries (e.g. USA, France, India, China and Russia). Averaged over 2010-2012, they estimate that ozone reduces wheat yields by a mean 9.9% in the northern hemisphere and 6.2% in the southern hemisphere, corresponding to some 85 Tg (million tonnes) of lost grain. Total production losses in developing countries receiving Official Development Assistance are 50% higher than those in developed countries, potentially reducing the possibility of achieving UN SDG2.

A major conclusion from the analysis is that ozone could reduce the potential yield benefits of increasing irrigation usage in response to climate change because added irrigation increases the uptake and subsequent negative effects of the pollutant.

The results show that mitigation of air pollution in a changing climate could play a vital role in achieving the above-mentioned UN SDG, whilst also contributing to other SDGs related to human health  and wellbeing, ecosystems and climate change.