The Impacts of Tropospheric Ozone Pollution on Crop Yield: Mechanisms, Quantification and Options for Mitigation

The purpose of this publication is to document the current knowledge of the damaging effects of tropospheric (ground-level) ozone pollution on food crops around the world and to discuss ways of mitigating these effects. The document makes the case for the inclusion of ozone in future crop yield predictions and recommends that management practices being developed to cope with climate change should take the effects of ozone into account. It is one of two guidance documents commissioned by the Expert Team on Agrometeorological Sciences as a contribution to the Standing Committee on Services for Agriculture of the WMO Commission for Weather, Climate, Hydrological, Marine and Related Environmental Services and Applications (SERCOM). The documents describe the impacts of the two forms of air pollution that are of greatest concern for crop yield at the global scale. The present document looks at the impact of tropospheric ozone; the other focuses on particulate matter and discusses the current knowledge of the combined effects of both pollutants.

This synthesis of current knowledge concludes, with a high level of confidence, that:

• There is robust evidence from field surveys, ozone exposure experiments and modelling that current concentrations of ozone are having a negative impact on crop yields in many of the world’s major agricultural areas;
• Ozone pollution is a “hidden” cause of reduced yield quantity and quality that is not usually accounted for in assessments of current and future food security or included in crop management plans;
• Ozone concentrations are rising and are predicted to continue to rise in many developing countries where security of food supplies is needed most.