Structure and composition of the forest

The beech cathedral

The beech cathedral takes up approximately 70 percent of the Sonian Forest. This makes the forest vulnerable. In an unvarying landscape like such as this one, fewer types of plants and animals can be found. Even in the soil, the number of useful insects and organisms is limited. In addition, more and more scientific studies show that climate change also has implications for the Sonian Forest. The ever-drier and -warmer summers are detrimental to the beech, except in the deep valleys.

Therefore, the three regions have decided in the future to reduce the portion of the forest that is devoted to beeches. At the same time, they want to preserve the characteristic landscape of the beech cathedral in certain parts of the forest.

Trees of all ages

A Sonian Forest with a greater variety of trees and of different ages—that should soon be the forest’s new look, with young and adult trees growing close together. The result: a varied and light-infused forest, where many animals and plants feel at home.

Lanes and notable trees

The stately rows of trees along the lanes are an important distinguishing feature of the Sonian Forest. We must preserve and restore this heritage. The many rare and unusual trees here also deserve this protection. Currently, Bruxelles Environnement and the Association for the Protection of the Trees in the Sonian Forestare  charting out the most notable trees.  A hundred have been identified and marked.

Parks and open areas

Throughout the course of history, parts of the Sonian Forest have been transformed into parks, arboreta or race tracks: theBois de la Cambre, the Solvay Park, thepark of Tervuren, the hippodromes of Watermael-Boitsfort and Groenendaal . These sites make the Sonian Forest rich in landscapes and habitats. Here you will find water gardens, unusual trees, grasslands and lawns, much different than the forest itself but no less valuable.


Along the perimeters of the forest, between these half-open areas and the Sonian Forest, live a great number of exceptional plants and animals which do not appear in the core of the forest. Moreover, these parks receive a great proportion of the visitors and in doing so form a natural buffer.