The Sonian Forest: Where beech trees meet bureaucracy
Just a few kilometres south-east of Brussels, beyond the last tram stop and the tidy residential avenues, begins one of Belgium’s most extraordinary natural sites: the Sonian Forest. With its slender, 50-metre-tall trees and sparse undergrowth, this forest is not only one of the country’s most iconic green spaces. It’s also a living symbol of how history, politics and ecology can intertwine in profoundly complex ways.
The story of the Sonian Forest – a 5,000-hectare patchwork of ancient beech stands, gravel paths, damp valleys and sunlit clearings – is one of loss, reinvention and resilience. A relic of the great Western European forest that once stretched from the North Sea to the Alps, the Sonian has been managed, harvested, fragmented and replanted for centuries. Its history follows the contours of Belgium’s own: from medieval monastic estates to French nationalisation, from Austrian forest reforms to industrial exploitation under Dutch rule. In just one century, between the early 1700s and the mid-1800s, more than three-fifths of the forest was cleared.
Yet what remained was gradually reclaimed. The Austrians began replanting with beech in the 18th century, favouring monocultures that now give the forest its striking, orderly appearance. In 2017, five of the Sonian’s core areas were added to the UNESCO World Heritage List for their ancient beech groves—some of the tallest and oldest in the world. But this recognition belies the reality that this forest, despite its grandeur, is under constant pressure.
Divided responsibility
The Sonian Forest lies on the fault lines of Belgian governance. Since the country became a federal state in 1993, responsibility for the forest has been divided between the Flemish, Brussels-Capital and Walloon regions. Each manages its own section according to its own laws, spatial plans and priorities. Brussels sees its part as a vital ecological lung; Flanders views it as a natural and recreational area; Wallonia, with only 6% of the total area, designates its part as a landscape heritage. Overlay this with EU designations – Natura 2000 sites, archaeological zones, nature reserves – and the result is a dizzying web of overlapping classifications and authorities.
Efforts to coordinate management date back to 2008, when the regions agreed on a common vision for the future of the forest. This ‘interregional structural vision’ aimed to restore ecological continuity, promote sustainable recreation and protect biodiversity. A decade later, the Sonian Forest Foundation was set up to harmonise activities across borders and act as a hub for cooperation between public authorities, scientists, communities and private landowners. But even seemingly minor issues – such as whether dogs should be kept on a lead – remain unresolved between the regions. Coordination is active, but slow, and the forest continues to suffer from fragmentation, recreational overuse and urban encroachment.
Human pressure
Nowhere is this tension more evident than in the relationship between the forest and the city that surrounds it. With more than two million visitors a year, the Sonian is a popular escape for walkers, joggers, cyclists and families. But this popularity comes at a cost. Human pressure on the landscape is high, and the ecological impacts of recreation – particularly off-trail movement, unleashed dogs and erosion – are only beginning to be understood.
It’s not just the plants and soil that suffer. The forest’s wildlife is also under stress.
The deer population is declining, despite a ban on hunting. Researchers point to several possible causes: habitat fragmentation, disease, reduced reproduction and roadkill. The forest is criss-crossed by motorways and a major railway line. Every year, cars kill foxes, martens, squirrels and amphibians during their seasonal migrations. Artificial lighting disrupts bat species. Yet these threats – so closely linked to infrastructure and mobility – are barely addressed in the regional management plans.
Mitigation efforts
Some mitigation work has started. New wildlife passages, fences and tunnels have been installed with EU funding. The first eco-passage has been completed in recent years through cooperation between regional authorities, municipalities and environmental agencies. A second was officially opened in February this year. But progress remains modest, and the threats are growing. Urbanisation continues to creep towards the forest’s edges, and climate change looms as an additional stressor.
Nevertheless, there is reason for cautious optimism. In all regions, authorities are increasingly relying on scientific research to inform their decisions. Long-term studies of species behaviour, ecological functioning and recreational impacts are being undertaken. Cross-regional cooperation, although imperfect, is improving. The presence of a dedicated foundation provides at least some continuity in vision and coordination. And public support for forest conservation remains strong.
Preserving pristine wilderness
In the Anthropocene, conservation is no longer about preserving pristine wilderness. It’s about negotiating space for nature within human-dominated landscapes – cities, suburbs, infrastructure corridors and recreational zones. The Sonian Forest, with its convoluted governance, immense ecological value and proximity to a major European capital, is a living case study of what conservation looks like in the 21st century. It is fragmented yet vital, compromised yet beloved, governed by many but in a sense owned by all.
And in the towering silence of its beech groves, it reminds us that even the most managed, urbanised and politicised landscapes still have the power to inspire awe – and to ask difficult questions about how we share space with the more than human world.