Other international initiatives are the Ministerial Conferences for the Protection of Forests in Europe (Strasbourg, 1990, Helsinki, 1993, Lisbon, 1998, Vienna, 2003, Warsaw, 2007), which led to the Pan-European Criteria and Indicators for Sustainable Forest Management, the Montreal Process on Sustainable Development of Temperate and Boreal Forests, and the UN Forum on Forests. They should be related to information on forest quality (e.g. species diversity, including tree and non-tree species, forest degradation, forest fragmentation), on output of and trade in forest products, and be complemented with data on forest management practices and protection measures. They present national averages that may conceal important variations among forests. Interpretability is however limited due to differences in the variables monitored. Historical data often lack comparability or are not available over longer periods. This is unevenly distributed, the ten most forest-rich countries accounting for two-thirds of total forest area.