Assessing the future global impacts of ozone on vegetation

TLDR

Ozone, a major secondary air pollutant, adversely affects crop yields, forest growth, and species composition, with emissions decreasing in North America and Europe but rising in Asia, and global background concentrations increasing, thereby altering plant responses over the coming century. This study evaluates whether current knowledge of ozone impact mechanisms and risk‑assessment tools can adequately assess the consequences of changing global ozone exposure patterns, and stresses the need for more holistic approaches. The authors propose new mechanistic models linking stomatal flux, detoxification, repair, and carbon allocation, and call for integrated frameworks that combine ozone, climate, nutrient, and water effects on plants, species, and ecosystems. Risk assessments that rely solely on external ozone concentration–plant response relationships are insufficient for addressing these emerging challenges.

Abstract

ABSTRACT Ozone is a major secondary air pollutant, the current concentrations of which have been shown to have significant adverse effects on crop yields, forest growth and species composition. In North America and Europe, emissions of ozone precursors are decreasing but in other regions of the world, especially Asia, where much less is known about its impacts, they are increasing rapidly. There is also evidence of an increase in global background ozone concentrations, which will lead to significant changes in global ozone exposure over this century, during which direct and indirect effects of other changes in the global atmosphere will also modify plant responses to ozone. This paper considers how far our current understanding of the mechanisms of ozone impacts, and the tools currently used for ozone risk assessment, are capable of evaluating the consequences of these changing global patterns of exposure to ozone. Risk assessment based on relationships between external concentration and plant response is inadequate for these new challenges. New models linking stomatal flux, and detoxification and repair processes, to carbon assimilation and allocation provide a more mechanistic basis for future risk assessments. However, there are a range of more complex secondary effects of ozone that are not considered in current risk assessment, and there is an urgent need to develop more holistic approaches linking the effects of ozone, climate, and nutrient and water availability, on individual plants, species interactions and ecosystem function.