Comparative analysis of harmonized forest area estimates for European countries

Harmonized forest area information provides an important basis for environmental modelling and policy-making at both national and international levels. Traditionally, this information has been provided by national forest inventory statistics but is now increasingly complemented with remote sensing tools. Reliability and harmonization of both sources are important aspects to ensure comparability and to enable the development of international forest scenarios. Initiatives with the purpose of harmonization of forest area for both sources are currently on going. Nevertheless, all forest area estimates contain uncertainties, which must be quantified and included in the error budget. This is a prerequisite for combining and comparing data. The purpose of this study is to compare, taking into account uncertainties, forest area estimates for year 2000 derived from four different harmonized satellite-based maps, covering Europe with recognized official forest statistics. It was found that the major cause of disagreements between official statistics and map-derived forest area originates from the general issue of accounting for land cover instead of land use. Consequently, CORINE land cover results had the best accordance with official statistics due to its focus on land use. The other maps overestimated the forest area in mountainous countries and showed underestimation in countries with large forest area or open forest formations.