Ozone pollution induced-yield loss of major staple crops in China and effects from COVID-19.

Surface ozone (O) pollution showed a continuous increasing trend during the recent decades in China, posing an increasing threat to food security. A wide range of yield reductions have been reported and thus more studies are needed to narrow down the uncertainty resulting from spatiotemporal accuracy of O metrics and extrapolation methods. Based on a high spatial resolution (0.1°) hourly surface O data, here we analyzed the spatiotemporal O pollution patterns and impacts on yield, production and economic losses for wheat, rice, and maize in China during 2005-2020. The accumulated O exposure over a threshold of 40 ppb (AOT40) increased by 10 % during 2005-2019, and a decrease of 5.56 % was observed in 2020 due to the COVID-19 lockdowns. Rising O pollution reduced national level wheat, rice and maize yields by 14.51 % ± 0.43 %, 11.10 % ± 0.6 %, and 3.99 % ± 0.11 %, respectively. A Business-As-Usual projection suggested that the relative yield loss (RYL) would potentially reach 8 %-18 % at the national scale by 2050 if no emission control is implemented. COVID-19 lockdowns in 2020 led to significantly reduced RYL for maize (0.52 %) and rice (2.17 %) but not for wheat (0.11 %), with the largest reduction (1.88 %-9.4 %) in North China Plain, highlighting the potential benefits of emission control. Our findings provided robust evidence that rising O pollution has significantly affected China's crop yields, production and economic losses, underscoring the urgent need to curb O pollution to safeguard food security, particularly in densely populated and industrialized regions.