Ozone pollution will compromise efforts to increase global wheat production

Abstract

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. Using a modelling method that accounts for the effects of soil moisture deficit and meteorological factors on the stomatal uptake of ozone, we 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. United States, France, India, China and Russia). Averaged over 2010-2012, we 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. Crucially, our analysis shows 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. We show that mitigation of air pollution in a changing climate could play a vital role in achieving the above-mentioned UN SDG, while also contributing to other SDGs related to human health and well-being, ecosystems and climate change.

Closing the global ozone yield gap: Quantification and cobenefits for multistress tolerance

“…The EMEP MSC‐W (European Monitoring and Evaluation Programme, Meteorological Synthesising Centre‐West) chemical transport model (version 4.16, Simpson, Bergström, Imhof, & Wind, ; Simpson et al., ) was used to derive daily POD 3 IAM (phytotoxic ozone dose above 3 nmol m −2 s −1 , parameterized for integrated assessment modelling, CLRTAP, ) values for the years 2010 to 2012 per 1° by 1° grid cell as described by Mills, Sharps et al. (). POD 3 IAM is parameterized for a generic crop represented by wheat (CLRTAP, ) and represents the accumulated stomatal uptake of ozone, modelled from the hourly mean values for ozone, temperature, vapour pressure deficit, irradiance and soil moisture (Mills, Sharps et al., ).…”

“…Whilst it is widely recognized that rapid breeding programmes will have a vital role to play in adaptations of crops to climate change (Atlin, Cairns, & Das, ), selection of traits for tolerance of one abiotic stress, tropospheric (ground level) ozone pollution, is currently omitted from such breeding programmes (Ainsworth, ; Frei, ). This is happening even though field experiments from nine countries representing three continents have shown that reducing ozone concentrations back to pre‐industrial levels would give an average wheat yield benefit of 8.4% globally (Pleijel, Broberg, Uddling, & Mills, ), a figure that is matched by modelling based on the stomatal uptake of the pollutant (Mills, Sharps et al., ). Furthermore, an earlier meta‐analysis of crop responses to ozone suggested that current ozone levels in the range 31–50 ppb (nmol/mol, v/v) are reducing the yield of major food crops by 5.3%–19% (Feng & Kobayashi, ).…”

Tropospheric Ozone Assessment Report: Present-day tropospheric ozone distribution and trends relevant to vegetation

“…Avnery et al, 2011;Van Dingenen et al, 2009) or stomatal ozone uptake (e.g. Mills et al, 2018;Mills et al, submitted). For perennial vegetation, there is good representation of data in mid-latitudes of the Northern Hemisphere where grassland and forested areas provide grazing, harvestable biomass and other ecosystem services.…”

Tropospheric ozone pollution reduces the yield of African crops

“…Many crops have been shown to be sensitive to ozone pollution, including staple foods such as rice (Akhtar et al, ), wheat (Wahid, ) and soybean (Betzelberger et al, ). Analysis of compiled data sets from many experiments has shown a wide range in ozone sensitivity between different crops, based on ozone concentration (Mills et al, ; Mills & Harmens, ; Mills, Sharps, Simpson, Pleijel, Broberg, et al, ). Model‐based studies using dose‐response functions from such data sets have indicated potential crop yield reductions due to ozone across wide regions of the world (Avnery, Mauzerall, Liu, & Horowitz, ; Mills, Pleijel, et al, ; Mills, Sharps, Simpson, Pleijel, Broberg, et al, ; Mills, Sharps, Simpson, Pleijel, Frei, et al, ; Van Dingenen et al, ).…”

“…Analysis of compiled data sets from many experiments has shown a wide range in ozone sensitivity between different crops, based on ozone concentration (Mills et al, ; Mills & Harmens, ; Mills, Sharps, Simpson, Pleijel, Broberg, et al, ). Model‐based studies using dose‐response functions from such data sets have indicated potential crop yield reductions due to ozone across wide regions of the world (Avnery, Mauzerall, Liu, & Horowitz, ; Mills, Pleijel, et al, ; Mills, Sharps, Simpson, Pleijel, Broberg, et al, ; Mills, Sharps, Simpson, Pleijel, Frei, et al, ; Van Dingenen et al, ). Experimental investigations have shown impacts of ambient ozone concentrations on a wide range of crop species in Europe and the USA by comparing responses of plants in filtered air to those in non‐filtered air (De Temmerman, Legrand, & Vandermeiren, ; Marzuoli, Finco, Chiesa, & Gerosa, ; Pleijel, Broberg, Uddling, & Mills, ).…”