1. To establish, on the basis of common methods, a periodic inventory of damage caused to forests, in particular by atmospheric pollution. 2. To establish or extend, in a co-ordinated and harmonious way, the network of observation plots required to draw up that inventory. 3. To conduct intensive, continuous surveillance of forestry ecosystems. 4. To establish or extend, in a co-ordinated and harmonious way, a network of permanent observation plots required for such intensive, continuous surveillance.