Since the last glacial period, the present Belgian forests evolved from a cold steppe vegetation to a closed temperate forest with climate-induced changes in its tree species composition.
Large parts of the forests have been influenced by human activities since 2,700 BC. In the 16th century, the forests were mainly managed for timber production. Deforestation from logging in the first half of the 19th Century reduced the forest area by half. Today, the forest area of Belgium does not even reach 23% of the country's national territory. A large part of the remaining area is hereby taken up by settlements.
The five Belgian World Heritage Beech Forests are all located within the boundaries of the Sonian Forest in Flanders, in the Brussels-Capital Region, and in Wallonia. These Forest Reserves are the only examples of Atlantic Beech Forest in Western Europe in the entire Natural World Natural Heritage series.
They provide a substantial area for natural processes near Brussels and can serve as a model area for the protection of primeval forests. The soils have remained unaffected since the last ice age. Due to its large number of impressive old-growth individual beech trees and entire beech stands, the Sonian Forest is unique in Western Europe. It harbours an impressive number of relict species, mainly beetles that live in dead wood and that characterise the long continuity of the beech forest and its natural structures.