A United Nations study says the health of Europe's forests is deteriorating, after years of steady recovery. The Geneva-based U.N. Economic Commission for Europe says air pollution is a major cause of the damage.
Forests cover about one third of Europe. They are valued for their timber, recreation, and environmental benefits.
But, the U.N. study says Europe's forests are in trouble. It says about 20 percent of 135,000 trees that were assessed this year were damaged, a significant deterioration from previous years.
A German government forestry expert, Thomas Haussman, says the forest damage is caused by climate, soil condition, pests, and to a large extent, air pollution, especially nitrogen pollution. "If present nitrogen pollution rates continue, half of the plots investigated may see the diversity of their forest vegetation diminish," he said. "And, these plots will have an increased vulnerability to drought stress, frost, pest; and diseases is to be feared. Also, an effect on tree roots is to be feared on one-third of those plots investigated."
The study by the Economic Commission for Europe says the main sources of nitrogen pollution are industries, traffic and agriculture. It says international action is needed to cut levels of nitrogen pollution, similar to international cooperation that has reduced levels of sulfur pollution, or acid rain.
Mr. Haussman says healthy forests offer economic and environmental benefits that should not be underestimated.
For instance, he says forests provide little help in the face of extreme weather, such as the floods in parts of Europe this year. But, he says, under more normal circumstances, forests can help protect mountain villages against avalanches and damage from flooding.