Ozone in the Mediterranean region: evidence of injury to vegetation.

Abstract Over the last 25 yr, the Mediterranean basin has become heavily industrialized, and as a consequence, reports of air pollution damage to forested areas in southern European countries have increased since the late 1970s. Among pollutants, ozone appears to be one of the most potentially dangerous, both because the meteorological conditions present in the Mediterranean region are particularly favourable to its formation and persistence, and because it is the most ubiquitous. The available evidence strongly suggests that ozone occurs at sufficient concentrations to cause injury to sensitive plant species, including trees. Foliar injury caused by ambient ozone exposures has been clearly identified on native herbs, shrubs and tree species within several areas in southern Europe. However, ozone uptake and response are modulated by environmental factors such as drought. Recent studies suggest a complex interaction between high radiation, drought and ozone response in Mediterranean tree species such as Aleppo pine (Pinus halepensis). More data are required before a full evaluation of the impact of ozone on Mediterranean forests can be achieved. Furthermore, additional research is needed to better understand and characterize the response of the Mediterranean ecosystems.