The present report is a description of the forest condition in Europe, based on te results of transnational and national surveys of the United Nations Economic Commission for Europe (UN/ECE) and the European Union (EU). National survey results from 32 European countries, referring to 29 739 sample plots with 648 425 sample trees are presented. The plots cover about 152.6 million hectares of forests. 29 of these countries have also submitted results of the 16 x 16 km grid (transnational survey). The results of the 1994 survey indicate that forest damage continues to be a serious problem in Europe, as a substantial proportion of the forests was defoliated and/or discoloured. Improvements and worsenings were found throughout the various climatic regions, however, forest condition in Europe has generally deteriorated. The transnational survey results for 1994 revealed that 26.4 % of the total sample of around 102 300 trees were defoliated by more than 25 % and were thus classified as damaged. This means and increase by 3.8 percent points compared to the respective value of 22.6 % in 1993. The total tree samples of 1993 and 1994 can be compared, but detailed analysis should be corrected for changes in the total sample. In 1994, 12.1 % of the total tree sample showed a discolouration of more than 10 %. This is 2.1 % higher than in 1993. As regards the two main species groups, 24.3 % of the total broadleaves and 28.0 % of the total conifers were found damaged in 1994. This indicates that the broadleaves are still in a slightly better condition. Among the most common species, the most severely affected broadleaved species group was Quercus spp. (deciduous), of which 32.4 % trees were damaged, followed by Other broadleaves with 27.5 % trees damaged. Abies spp. and Picea spp. were the most affected of the common coniferous species with 32.9 % and 30.2 %, respectively. In order to be able to trace the development of forest condition over several years without distortion due to differences in the samples, special tree and plot samples which were common to certain survey years were analyzed. Such common samples were determined for the periods 1993-1994 and 1988-1994. The share of damaged Common Sample Trees (CSTs) of 1993-1994 increased within that period from 23.1 % to 26.2 %. Of the individual regions, the largest increase (from 16.2 % to 21.9 %) occurred in in the Mediterranean (higher) region, particularly in Quercus suber, Quercus ilex and Eucalyptus spp., and was mainly attributed to heat and drought. However, the latter species showed the lowest damage in the mediterranean regions. A similarly high increase in damage trees (from 27.2 % to 32.6 %) was found for the Continental region, where Abies alba and Quercus spp. in Romania were particularly affected and damage was mainly attributed to drought and local air pollution. In the Sub-atlantic region, the respective increase (from 39.3 % to 43.8 %) war partly due to summer drought, subsequent insect attack and local air pollution in Pinus sylvestris, Picea abies, Fagus sylvatica and Quercus spp. in the main damage areas of Germany, the Czech Republic, Poland and the Slovak Republic. In the subsample of the common trees of the surveys from 1988 to 1994, the development of the defoliation of 12 species was analyzed. With the exception of Abies alba, the proportion of damaged trees increased in all species during this period. Among the conifers, although Picea sitchensis still indicates the greatest increase from 2.3 % in 1988 to 20.3 % in 1994 there has been some improvement from 1993 to 1994. This increase is thought to be mainly caused by attacks of Elatobium abietum (green spruce aphid). A similarly alarming deterioration appeared in Pinus halepensis, the damaged share of which increased from 5.2 % in 1988 to 22.1 % in 1994. In contrast, the respective proportion of Abies alba diminished slightly from 25.8 % to 23.9 %. Abies alba had its largest share of trees defoliated, namely 30.1 %, in 1993. Concerning Quercus robur, a little improvement occurred in 1994, however, its damaged share increased remarkably from 13.0 % in 1988 to 24.9 % in 1994. In 1994, adverse weather conditions, particularly drought and heat, as well as insects, fungi, game, action of man, air pollution and forest fires were the most important probable causes for the observed defoliation and discolouration, as reported both in the national and the transnational surveys. There were only a few reports on known pollution sources to have direct impact on forest condition. However, there might be more widespread effects of air pollution, which could not be found in the assessment. According to the results of the national surveys, 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 exceed the critical levels and loads for forest ecosystems. These countries, in which a high level of air pollution has been detected, regard air pollution as the most important factor causing forest damage. The majority of the remaining countries consider air pollution as a predisposing, accompanying and locally triggering factor for the weakening of forest ecosystems. The survey results reveal a large spatial and temporal variation. It is therefore necessary to continue the monitoring on Level I and to foster synoptical evaluations of its results together with other large-scale ecological parameters in order to verifiy effects caused by long-range transboundary air pollution. It is planned to evaluate the complete Level I dataset in the future. In addition to the Level I monitoring, for the recognition of factors and processes with special regard to the impact of air pollutants on the more common forest ecosystems an intensive monitoring (Level II) has been designed and is under implementation. This was accomplished by means of a number of selected permanent monitoring plots, on which besides crown condition assessment also a soil inventory, foliar analyses, increment studies, deposition measurements and meteorological studies are being conducted. The report also outlines possible future development in programme monitoring activities and in assessment and reporting of the results.
