The main objective of the present report is a condensed description of the condition of forests in Europe, as it has been assessed by transnational and national surveys of the United Nations Economic Commission for Europe (UN/ECE) and the European Union (EU). The report presents survey results from 35 European countries, referring to about 26 000 sample plots with about 558 000 sample trees. Of 222 million hectares of forests in Europe as reported by the participating countries, around 181 million hectares have been covered by the surveys (3 million less than in 1992). The results of the 1993 survey indicate that forest damage continues to be a problem in Europe, as a significant proportion of the forests shows signs of defoliation and/or discolouration. The transnational survey results for 1993 revealed that 22.6% of the total sample of around 102 800 trees had been defoliated by more than 25% and are thus classified as damaged. The respective value in 1992 was 23.5%, which was 0.9 percent points higher than this year. In 1993 the share of trees with a discolouration of more than 10% was 10.0% of the total tree sample. This change is insignificant (0.1 percent points lower) as compared with the previous year (10.1%). As regards the two main species groups, 20.4% of the total broadleaves were damaged in 1993. This inidcates that the broadleaves are now in a slightly better condition than the conifers, of which 23.9% were damaged. Among the most common species, the most severely affected broadleaved species was Quercus spp. (deciduous) with 27.1% damaged trees, followed by Other broadleaves with 22.7% trees damaged. Among the conifers, Abies spp. and Picea spp. showed the highest percentages of trees classified as damaged (36.7% and 26.5%, respectively). In the subsample of common trees, the proportion damaged increased between 1988 and 1993 in all of the 12 species analyzed. Among the conifers, Picea sitchensis showed the greatest increase, from 4,6% in 1988 to 33.8% in 1993. This was probably due to Elatobium. Amongst broadleaved species, there was a dramatic increase in damage in Quercus suber, from 0.7% in 1988 to 44.0% in 1991, but the share of damaged trees decreased rapidly from 36.2% in 1992 to 9.5% in 1993. Damage in Quercus robur increased remarkably from 12.9% in 1988 to 26.8% in 1993. In both the national and the transnational survey the most important probable causes for the observed defoliation and discolouration were reported to be adverse weather conditions, insects, fungi, air pollution and forest fires. Very little direct impact from known pollution sources was reported, but this does not exclude the possibility of more widespread effects of air pollution. Particularly in the main damage areas of some countries, but also in several other regions, air pollution is considered as of major concern, because the atmospheric concentrations and the depositions of several air pollutants are thought to exceed the critical levels and loads for forest ecosystems. These countries regard air pollution as the most important factor causing forest damage. The majority of the remaining countries consider air pollution as a predisposing factor leading to the weakening of forest ecosystems. The great spatial and temporal variation in the survey results emphasizes the importance of continued monitoring of defoliation and discolouration and additional assessments of various ecological data which may contribute to a better understanding of cause-effect relationships. Therefore, within the cooperation between UN/ECE and EU, in addition to the large scale crown condition assessment, an integrated monitoring system is being established. This intensive monitoring aims at the recognition of factors and processes with special regard to the impact of air pollutants on the more common forest ecosystems. This is accomplished by means of a number of subjectively selected permanent monitoring plots, on which a soil inventory, foliar analyses, deposition measurements and increment studies will be conducted.
