Agenda 21 recommends collecting, consolidating and exchanging existing information and establishing baseline information on aspects relevant to this area, including: consolidating information on forest conditions and site-influencing imissions and emissions; consolidating and updating land-use and forest inventory and management information for management and land-use planning of wood and non-wood resources, including data on shifting cultivation and other agents of forest destruction.
According to a 1999 report, the EU member states, as well as most other European countries, have been systematically monitoring the state of their forests since 1986. They have been doing this in two ways. They have been monitoring the condition of the trees in some 5,700 observation plots, each 16 km by 16 km. These plots are located in all 15 EU countries and 16 other countries, and the total number of trees they contain is over 127,000. Thanks to this extensive monitoring, it is possible to make a general assessment of crown condition - that is to say, the condition of those parts of the trees which are covered by either leaves or needles. In addition, 860 of the observation plots are subject to intensive monitoring. Detailed studies are made of the substances, whether chemical or biological, which attack trees, in order to determine the causes of the diseases they are suffering from.