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Looking into the past and future of Flanders’ ancient woodlands

In the majestic Flandres Woods of Brabant, sustainable forest management plays a crucial role in balancing ecological, societal, and economic priorities. Unfortunately, this is becoming more challenging as climate change increases the occurrence of windstorms, drought, pests and diseases.

And there is a lot at stake: the woodlands are of high conservation value due to being home to important species such as the honey buzzard and the middle-spotted woodpecker, while also providing a source of wood and recreational sites for the public

The mission of the Horizon Europe project INFORMA in the area is to propose management options that cater for different needs, expectations and pressures in future climate scenarios. Read on to find more about our case study in Belgium!

Among the most beautiful and oldest forests in Belgium, the Woods of Brabant (Brabantse Wouden) are characterised by more than 10,000 hectares of Atlantic and Subatlantic forest, abundant in oak and beech trees, with an admixture of maples and pines. The larger areas of Meerdaal, Halle and Sonian forests alternate with smaller forest patches, open fields, and urban areas, creating a mosaic in the landscape.

The forests are partly under strict protection (about 600 ha of strict reserves plus smaller set-aside patches), while other sections are managed for multiple purposes. In the managed areas, small-scale close-to-nature management is the rule, but there are also patches with more intensive management, mostly to foster the conversion of conifer to broadleaved forest. The management aims to ensure that the woods retain their beauty, ecological functionality, and wood production capacity in times of climate change. In order to do so, management practices are adapting to account for more frequent windstorms, drought, pests, and diseases.

All forests in the Woods of Brabant have a high natural value: They are ancient woodland sites with rich fauna and flora. The term “ancient woodlands” refers to the fact that they have been permanently forested, at least since their oldest topographic map of 1770, but most probably since the early Middle Age, a reason why they are all included in the Natura 2000 network of European protected areas.

As currently the woodlands are located within a highly urbanised landscape, recreation plays an important role in these forests, receiving over 2 million visitors per year. Management planning and infrastructure therefore need to cater for this high recreational pressure.

Satellite view of the Woods of Brabant. In white, from left to right: Hallerbos, Sonian, and Meerdaal-Heverlee forests, surrounded by dense urban infrastructure and intensive agriculture in their immediate surroundings. Source: Google Maps.

Forest management history and practice

The forests of Hallerbos, Meerdaal, and Sonian Forest are all public forests, managed by the regional forest management service. They are shaped by many centuries of intensive but sustainable forest management, interspaced with periods of instability and plundering.

The Hallerbos and Meerdaal forests were traditionally managed as mixed coppice-with-standards forests, dominated by oak. The Meerdaal forest was gradually transformed into a high forest over the last century (characterised by large, tall mature trees with a closed canopy). It consists mainly of oak and beech, with many of the old oaks still preserved and reaching the age of 200-250 years. Hallerbos was heavily impacted by fellings during the First World War and completely replanted with stands of beech and oak in the 1920s. On sandy outcrops, stands of pine and larch were planted in both forests.

The Sonian forest has a long tradition as a high forest, mainly of beech. The forest has been renowned for its high-quality beech trees. Over the last 150 years, managers have been reluctant to perform final harvesting due to visitor protests and political pressure. This explains the high density of old and impressive trees. While the even-aged structure was long considered a problem from a silvicultural point of view, the old beech stands are now seen as recreational and ecological assets of the forest.

Over the last decades, these forests were mainly managed through selective high thinnings, a type of thinning to open up the forest canopy. Final harvest was mainly done in small group cuttings. In the conifer stands, some larger final fellings were performed. Also, some larger fellings were done in beech stands both in the Meerdaal and Sonian forests, in both cases because of the conversion of the stands to other dominant tree species (e.g. oak and lime) in order to enhance the diversification of the forest.

A forest stand in Tranendal, Hallerbos. When bluebells are flowering, large numbers of visitors from far and wide come to see this natural spectacle. Source: hallerbos.be

Challenges for conservation and recreation

Counting among the richest and most valuable oak and beech forests in Flanders, the Woods of Brabant harbour a rich typical fauna and flora of Atlantic beech and oak forests. The sites are important habitats for species such as the honey buzzard, woodpeckers as well as bats. Also, the stag beetle has some of its last populations in Flanders on the edges of these forests.

Apart from the legal protection under the Natura 2000 network, there is also a strong commitment to nature conservation in the local management planning. Strict reserves and smaller set-asides have been designated to protect a representative network of the oldest stands in the forest, and within the managed stands, efforts are made to conserve habitat trees, old trees, and increase the amount of deadwood. This already resulted in the return of species like the middle-spotted woodpecker. Furthermore. the reserves within the Sonian Forest form part of the UNESCO World Natural Heritage Site “Ancient and Primeval Beech Forests of the Carpathians and other parts of Europe”.

Important challenges to the conservation efforts are the strong fragmentation of the forests, surrounded by intensive agriculture and infrastructure (e.g. roads, railways, and built-up areas), and related atmospheric deposition. These depositions have diminished over the last decades, resulting in a slow but gradual recovery of the natural vegetation.

Another challenge for forest managers is pressure from the public. These forests have very high numbers of visitors, coming from the nearby cities. They need to be accommodated, and streamlined, by providing parking areas, hiking, and biking trails etc. This public also became more empowered and informed, leading to sometimes criticism of the management of the forest, even up to challenging certain harvests in court. To prevent conflicts with the public, forest management avoids interventions with strong ‘visual’ impact, such as large final fellings and organises public hearings and excursions to explain the management approach.

INFORMA contributions to the management of the Woods of Brabant

INFORMA’s research activities in the area are led by two institutions: the Research Institute Nature and Forest (INBO) and KU Leuven.

INFORMA’s activities will contribute to the sustainable management of the forests in several ways. First of all, we aim to gain a better understanding about the differences between managed and unmanaged forest stands in terms of carbon sequestration, biodiversity conservation and other ecosystem services. Second, we provide new modeling to monitor and predict the ecosystem services flow to be expected from these forests in times of climate change. And third, we will develop new cost-efficient monitoring tools to monitor and possibly certify the carbon sequestration in these forests, as an important contribution to climate change mitigation.

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