Global flux-based ozone risk assessment for wheat up to 2100 under different climate scenarios

Abstract. The negative effects of tropospheric ozone (O₃) on vegetation can lead to reduced photosynthesis, accelerated leaf senescence, and other negative outcomes which affect crop yields and biodiversity. This study presents a flux-based assessment of the global impact of O₃ on bread wheat (Triticum aestivum) for the 21^st century, under various climate scenarios (Shared Socioeconomic Pathways, SSPs). A dual-sink big-leaf dry deposition model is employed to estimate the phytotoxic ozone dose (POD) absorbed by wheat through stomata, integrating data from two Earth System Models (ESMs) from the Coupled Model Intercomparison Project 6 (CMIP6). The study explores spatial and temporal variations in O₃ concentrations and the effects of climate variables on stomatal conductance, explaining changes in POD from the present time to the century’s end. The results indicate significant regional disparities in O₃ dose for wheat, particularly under weak O₃ precursor emissions control scenarios. The most vulnerable regions include Northern Europe, East China, and the Southern and Eastern edges of the Tibetan Plateau, where the POD increase by the end of the century is expected to be most pronounced. Conversely, POD decreases worldwide under stringent pollution emission control scenarios. However, in some regions, changes in POD may be driven more by climate variables and their interaction with O₃, rather than by O₃ concentrations alone. Therefore, this study emphasizes the need for effective emission mitigation policies of both O₃ precursors and greenhouse gases to preserve global food security from O₃ damages.