Although air quality in Europe has improved, trees are still under stress. Air pollution and depositions, especially of sulphur, have been reduced; however, past depositions accumulated in soils may lead to higher levels of nitrogen, sulphate and soil acidity, making forests more vulnerable to environmental stress and changing climatic conditions. Tree crown condition has stabilized, but defoliation levels are still high in most regions, indicating that trees have a reduced potential to withstand adverse environmental impacts. Further reductions in emissions are needed to improve ecosystem health and vitality. Forests in Europe have suffered severe storm damages, and forest fires continue to be a major challenge. Since 1999, there has been extensive storm damage in Europe almost annually. Hundreds of thousands of hectares of forest are burnt annually. While the number of forest fires increased, the area burnt did not increase in the period 2000-2005, mainly due to more effective fire suppression in many countries.
