Ozone impacts on vegetation

Currently the concentrations of ozone in the atmosphere across Europe are regularly exceeding levels that are predicted to result in adverse effects on vegetation (e.g. crop yield losses, visible leaf injury).

The ICP Vegetation programme, managed by the UK Centre for Ecology & Hydrology (UKCEH), coordinates research on the harmful effects of ozone pollution on European vegetation. New critical ozone levels, specific to vegetation and growing conditions, have been included in UN transboundary air pollution policies.

Levels of ozone pollution in the air can adversely affect large areas of European vegetation, causing, for example, leaf damage and reduced root growth, crop yields and tolerance of drought.

The ICP Vegetation programme is investigating the impacts of air pollutants on vegetation.  It forms part of the United Nations Economic Commission for Europe Convention (UNECE) on Long-Range Transboundary Air Pollution (LRTAP).

The programme involves scientists in 33 European countries plus the USA and Canada. It is coordinated from the UK by UKCEH at Bangor.

Knowing the ozone concentration in the air provides only a partial picture of its potential for damage. The gas’s impact varies according to the vegetation type - some species are more sensitive than others. Different amounts of ozone are taken up by different species through the pores in the leaf surface (stomata) under different climatic and soil conditions.

Through the ICP Vegetation programme, scientists have undertaken a comprehensive assessment of ozone’s impacts on crops and natural ecosystems across Europe. Maps of stomatal flux were found to be better at predicting the occurrence of ozone damage to vegetation seen in the field than maps that were based on ozone concentration. Worryingly, the data gathered has confirmed that ozone levels in the air are harming vegetation across most of Europe: Ozone injury has been detected at every site in the pan-European network including in the UK.

You can read more about the experimental facilities here. 

Following two international workshops in 2009-10 chaired by Dr Gina Mills of UKCEH, new critical levels for ozone were set. These levels were presented to the UN LRTAP Convention and have been incorporated into UN policy on transboundary air pollution. This has a direct impact on food security of the UK. As a result the critical levels for ozone were revised with the introduction of 10 policy-relevant indicators based on the biologically relevant ozone flux to the leaf. The programme will assess the economic losses caused by ozone effects on crop yield in the UK.

It is anticipated that the data analysis being conducted for this report will result in new climate-relevant critical levels. In addition, UKCEH undertake knowledge exchange activities to raise awareness of the problem directly with UK farmers.