Surface ozone impacts on major crop production in China from 2010 to 2017

Abstract. Exposure to elevated surface ozone is damaging to crops. In this study, we performed an analysis of temporal and spatial distributions of relative yield losses (RYLs) attributable to surface ozone for major crops in China from 2010 to 2017, by applying the AOT40 metrics (hourly ozone concentration over a threshold of 40 ppbv during the growing season) simulated by chemical transport model. The major crops in China include wheat, rice (including double early & late rice, and single rice), maize (including north and south maize) and soybean. The aggregated production and associated economic losses in China and major provinces were evaluated by combing annual crop production yields with crop purchase prices. We estimated that, from our model simulations, the national annual average AOT40 in China increased from 21.98 ppm h in 2010 to 23.85 ppm h 2017, with a peak value of 35.69 ppm h in 2014. There exists significant spatial heterogeneity for the AOT40 and RYLs across the four crops due to the different growing seasons for each crop. We estimated that national mean RYLs were 11.45 %–19.74 % for wheat, 7.59 %–9.29 % for rice, 0.07 %–3.35 % for maize, and 0.87 %–2.74 % for soybean during 2010 to 2017. The associated ozone-induced annual average crop yield losses were estimated 13.81–36.51 million metric tons (Mt) for wheat, 16.89–20.03 million Mt for rice, 4.59–8.17 million Mt for maize, and 0.27–0.34 million Mt for soybean, which accounted for annual average economic loss of $9.55 billion, $8.53 billion, $2.23 billion, and $0.22 billion individually over the 8 years. Our results provide first, long-term quantitative estimation of crops yield losses and their economic cost from surface ozone exposure in China before and after the China Clean Air Act, and improve the understanding of the spatial sensitivity of Chinese crops to ozone impacts.