Ozone

Major results for ozone are:

• There is evidence of widespread ozone damage to vegetation in Europe.  Ambient levels of ozone cause visible leaf damage, reduce crop yield, affect crop quality and reduce the biomass of sensitive plant species.  (Evidence report)

• Vegetation at sites with the highest ozone concentration may not have the highest uptake of ozone because of the modifying effects of climatic conditions (such as temperature, humidity, soil dryness) on stomatal conductance. Therefore, a stomatal flux-based approach was developed to establish ozone critical levels for vegetation.  This flux-based approach is better at predicting areas at risk of ozone damage.  The flux-based method can take into account the modifying affect of the future climate.  (Evidence report)

• Ozone critical levels for vegetation are regularly exceeded across Europe.

• Policies only aiming at protecting human health will not protect vegetation from adverse effects of ozone in the northern third of the European area.   (Annual report 2007/8)

• At current climatic conditions, a reduction of 75% of the generic ozone flux to crop species will result in more than 90% of EMEP grid squares, currently showing evidence of ozone damage to vegetation, being within the ‘damage unlikely’ category. (Annual report 2008/9)

• Ozone-induced yield losses for 23 crops (mainly arable) in 47 countries in Europe were estimated to be €6.7 billion per year for year 2000 ozone concentrations.  (Holland et al., 2006)

• Several plant communities of (semi-)natural vegetation were identified as potentially ozone-sensitive after calculating the percentage of ozone-sensitive species within each community. (Mills et al., 2007b)

• Evidence suggests that ozone and nitrogen can have both synergistic and antagonistic effects on species and ecosystem processes; they may interact in unpredictable ways to affect plant communities.  (Annual report 2005/6; Annual report 2008/9)