Air pollution is causing declining condition of trees across Europe

The research, conducted by the European Union and the Economic Commission for Europe of the United Nations (UN/ECE), found a deterioration in the condition of the main tree species across Europe in 1999. The trend is most pronounced for broadleaved trees such as beech and several oak species, as well as maritime pine. On average, defoliation between 1992 and 1999 worsened on approximately 30% of the observation plots.

“The forest has high economic and social values which, in the common interest of our quality of life in Europe, have to be preserved,” said Franz Fischler, European Commissioner for Agriculture, Rural Development and Fisheries. “A sustainable forest management supplies our current demand for wood and other forest products and thereby forms the basis for the wood industry, which employs 2.2 million people throughout the European Union.”

The forest damage is being attributed at present to a complex system of multiple stress factors, according to the report. These include natural stresses, such as drought and insect pests, and man-made stress factors such as ozone and acid rain.

The condition of soils across Europe is also giving cause for concern, say the researchers, with widespread acidification (see related story). Central Europe, where almost all acidified soils are located, is the region with the highest air pollution and the highest defoliation of trees, say the researchers. Aluminium, released by the acidification in soils, was found at levels higher than is considered acceptable for trees on 10 to 15% of plots, and levels of nitrate considered unacceptable for drinking water were found at 18% of the plots.

However, there was an improvement in the condition of trees at 15% of observation plots, with the only tree species to have shown a recovery being Scots pine and Holm oak.

Long-term development of European forests must be seen in a different way for individual tree species and regions, says the report. There is clear improvement for western and central European areas, but a worsening in the Mediterranean region, with a considerable average increase in the defoliation of nearly all tree species during the last five years. In the northern regions there are no clear trends.

Further increased efforts on the collection and evaluation of European forests are required from Member States, the European Commission, and UN/ECE, says Fischler.