The impact of ground-level ozone (O3) on vegetation is largely under-investigated at global scale despite worldwide large areas are exposed to high surface O3 levels and concentrations are expected to increase in the next future. To explore future potential impacts of O3 on vegetation, we compared historical and projected O3 concentrations simulated by six global atmospheric chemistry transport models on the basis of three representative concentration pathways emission scenarios (i.e. RCP 2.6, 4.5, 8.5). To assess changes in the potential O3 threat to vegetation, we used the AOT40 metric. Results point out a significant overrun of AOT40 in comparison with the recommendations of UNECE for the protection of vegetation. In fact, many areas of the northern hemisphere show that AOT40-based critical levels will be exceeded by a factor of at least 10 under RCP8.5. Changes in surface O3 by 2100 range from about + 4-5 ppb worldwide in RCP8.5 scenario to reductions of about 2-10 ppb in the RCP2.6 scenario. The risk of O3 injury for vegetation decreased by 61% and 47% under RCP2.6 and RCP4.5, respectively and increased by 70% under RCP8.5. Key biodiversity areas in South and North Asia, central Africa and Northern America were identified as being at risk from high O3 concentrations. To better evaluate the regional exposure of ecosystems to O3 pollution, we recommend the use of improved chemistry-climate modelling system, fully coupled with dynamic vegetation models. We thank the project MOTTLES “Monitoring ozone injury for setting new critical levels” (LIFE15 ENV/IT/000183) for financial support.
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