Tropospheric ozone is the most important single air pollutant of importance to forests in eastern United States. Both broadleaf and needled trees may suffer premature foliar senescence following even low ozone exposure years. Genetic sensitivity within species is likewise prevalent.

Calcium avaiability to forests has been shown to be reduced by acidic deposition in several ways including: increased leaching from foliage, increased leaching from soils, and decreased availability from poorly buffered soils when aluminium is mobilized. Studies documented that acidic deposition has altered the growth and vigour of red spruce during the past three decades by changing calcium availability.

Experimental research on the physiology of tree seedlings under simulated climate and doubled carbon dioxide can rarely be extrapolated to grown forests. Climatological research has demonstrated a warming trend in the north and a cooling trend in the south of China. However, the changing climate has not caused the death of forests. Projecting the impact of climate change on forest distribution and growth using current GCMs seems to be the only method available.

Enhanced forest growth in combination with relatively high Nitrogen deposition may result in further pedologic and nutritional changes and an even greater destabilisation of forest ecosystems.

The national forest inventory of Switzerland is a large-scale assessment of the condition and changes in Swiss forests. Some of the most important advantages of the NFI are its permanence, the long-term and flexible inventory design, the high data-quality and the compatibility with the damage inventory.