The Sonian City is the area including and surrounding the Sonian Forest in Belgium. It is located at the south-eastern periphery of the country's capital city, Brussels, and its territory spans across three regions (the Brussels Capital Region, Flanders, and Wallonia). While the Sonian Forest (FR Forêt de Soignes, NL Zoniënwoud) is a forest widely studied and with defined boundaries, the Sonian City is an operational concept to be developed and researched within the Clearing House project. It consists of the Sonian Forest, at its core (i.e., 4,383 hectares of non-urbanised land, protected by several decrees as Natura 2000, Forest and natural reserve and regional planning tools), and the neighbouring areas where the forest ecosystem stretches toward and intertwines with the urban areas.
State of the Urban Forest
Understanding the state of the urban forest in the area, requires a combined analysis of both the state of the forest and of the state of the city. The forest ecosystem is dominated by the beechwood (“Kathedraal beukenhout - Hêtraie cathédrale - Beechwood Cathedral”) hosting an exceptional fauna and flora. Since the largest part of the forest has never been cleared, it has preserved a relief and soils that have not been modified by agriculture for more than 10,000 years. The Sonian Forest is characterised by micro and macro ecosystemic linkages whose continuity is strongly influenced by the surrounding developed land. An in-depth study of the ecological structure of the forest has brought to light the main threats to the forest, which include the mobility infrastructure and cuts through the forest breaking its ecological structure, and the recreative pressure.
The embeddedness of the Sonian forest in the urban fabric, implies that it is not sufficient to look into how urbanisation represents a pressure onto the forest but look into how the forest stretches into the city: in this context, virtually all urban trees and urban green spaces (and not only the remnants of the millenary forest) become the dots to be linked to draw the portray of the Sonian city. Research based on remote sensing show that vegetation covers 54% of the regional territory, making Brussels a rather green city. At the same time, important inequalities are present throughout the regional territory: this number drops to 30% in the first belt (premiere couronne), and even to 10% in the city centre. In addition, it should be noted that a large share of these green areas was inaccessible to the public (private gardens or estates, spaces associated with roads, railway embankments, housing complexes, etc.). A 2009 inventory calculates that only 19% of the regional territory could be considered as green public space, which means a regional average of 28 m2/habitant. Crucial challenges include the provision of high-quality green space, its fair distribution throughout the territory, and its ecological connectivity.
Governance, planning and policy landscape
The territory of the Sonian City spans different administrative boundaries. Relevant authorities include the local governments of 11 municipalities: the provincial governments of the Flemish Brabant and the Walloon Brabant, and the regional governments of the Brussels Capital Region, Flanders and Wallonia. The federal government and the Language Communities have certain competences in this territory, but only play a rather indirect role. This administrative fragmentation implies that the planning approach is not uniform throughout the territory, but follows the borders of the three regions, resulting in three separate planning frameworks.
As far as the core area is concerned, one of the most important policy instruments is the "Natura 2000" network, in which the 'core' part of the forest and some neighbouring green areas are registered. This is a European network of natural or semi-natural sites important for both the fauna and flora that live there. Unlike many nature reserves, Natura 2000 areas are not "closed" reserves: human activities are still allowed as long as they do not compromise the "objectives for nature" in the area. Building on it, every region also has a management plan for the portion of forest under their jurisdiction. To foster cooperation between the different regions, also the Structural plan for the Sonian Forest has been drawn up and a platform of permanent cooperation was established in the form of the Sonian Forest Foundation. For the city/forest areas surrounding this forest core, the landscape of policies and regulations impacting UFBS is much more fragmented. Some provisions are included in more general policy and planning tools (i.e. not immediately targeting the environment), at the regional, provincial and communal level. There are also some policy tools targeting environmental issues.
Participation citizen science & contestation
Albeit not new, the concept of participatory governance, as an institutionalised process of citizen involvement in policy making is in its infancy. While different policies on the environment and support for citizen initiatives have been developed, these seem to be still at the trial-and-error stage in terms of how they interact and collaborate with new forms of citizen engagement. Today, it is mainly at the communal level that the new forms of participatory governance take place, with many communes having a deputy mayor charged with participation and different initiatives. In relation to UFNBS, a number of projects are worth attention such as the "Renforcement du Réseau Ecologique Bruxellois", which includes efforts to define the nature development strategies of selected neighbourhood via participatory processes. Citizen science, as a specific form of participation, is becoming increasingly popular. In the last years there has been a wealth of projects initiated – or supported – by public authorities: e.g. the portal observations.be, which allows citizens to encode observations about local flora and fauna; or the Wood Wide Web, consisting of a crowdsourced crossmedia inventory of remarkable trees across the regional territory. In addition to "projects" and institutionally-backed activities to enhance ecological connectivity, in the area there are numerous cases where citizens have also mobilised to protect tree ecosystems in Brussels from land speculations and urban development plans. This was also in conflict with the authorities.
The Sonian City and the Sonian Forest are located in the south-eastern part of a metropolitan area of about 2.5 - 3 million inhabitant, gravitating around Brussels. The morphology of the agglomeration is determined by the historical development which proceeds in concentric circles, from Brussels city centre to the first and second ring roads and then to the suburbs, characterised by urbanisation around small, closely spaced cores. From a social, demographic and economic perspective, the area is characterised by a strong duality between the urban core and the periphery, which again follows different paths in the Flemish and in the Walloon parts of the zone. In terms of population density, the centre of gravity of the metropolitan areas is located in the very heart of Brussels. High values are also achieved in areas of secondary cities. Overall, the densities are lower in Wallonia, as opposed to the Flemish part of the area characterised by scattered housing. The same duality is observed in socio-economic terms. Brussels Capital region presents an average income that is lower than in the other regions (14.372 euros per capita, vs 18.331 euros at the national level), and almost a third of the residents live below the at-risk-of-poverty line. The rest of the metropolitan area scores better than the Belgian average, with the provinces of Flemish Brabant and of Wallon Brabant presenting the highest average income in the country (21.963 and 21.576 euros per person, respectively). The area around the Sonian forest, stands out in the map as one of the most affluent of the area. The population is highly qualified with a very high average taxable income, the housing market is the most expensive, there is little unemployment and little share of blue-collar workers.
Major challenges & knowledge gaps
One of the biggest problems for the enhancement and maintenance of the urban forest and its ecological connectivity is the virtually never stopping land development, which reducing the sheer number of green areas of all kinds, but also inasmuch as it is done with little consideration of the translocal ecological landscape, critically hampering ecological connectivity. A crucial dilemma is sometimes referred to: that is on whether it is preferable to densify the urban core, thereby reducing green spaces and connectivity there where is already scarce; or in the periphery, encroaching on existing open spaces and natural areas. The latter is a particularly relevant challenge at the edges of the Sonian forest, where return to land development can be extremely high. Another important question, however, precedes this dilemma, and concerns whether urban development is necessary at all considering the current demographic trends, and the fact that all too often opportunities are missed in terms of "re-greening" large quasi-public spaces (e.g. squares, sport facilities...). A critical component of urbanisation-related challenges to ecological connectivity concerns the development of mobility infrastructures. Roads (and to a lesser extent railroad) represent a source of fragmentation and destruction of tree ecosystems, especially -but not only- in the core part of the forest.
Overall, the current legislation seems to be insufficient to protect, and in any case to foster ecological connectivity, because of a virtual absence of juridical value for the regional ecological network. Existing urban planning regulation are often breached, also because of the little monitoring efforts, derogated on, and modified to allow for new developments. There is virtually no regulation to preserve greenfield, with the only one concerning the preservation of large ponds. Issue related to the governance and the management of existing tree spaces in the city are related to the maintenance costs of trees on public land, but also the training of staff, which includes little (or no) attention to biodiversity and eco-connectivity questions. Often the necessary expertise is simply missing at the relevant decision-making level. In addition, the good governance of a complex and articulated field such as the protection and enhancement of ecological connectivity is also hampered by the institutional fragmentation and the lack of cooperation between different levels of governance and policy sectors.
Lack of knowledge about UFNBS does not seem to a challenge as such. Consultation among local stakeholders made emerge a rather widespread consensus that already a lot of knowledge is available for the area, and that the emphasis should be placed in identifying venues for translating that knowledge into policy action (e.g. knowledge-based policy tools, inventories of relevant academic literature, inventories of existing laws and regulations, methods for effective awareness raising ... ), and to bridge the gap between expertise on urban planning and biodiversity conservations expertise. An interesting aspect concerns the cartography of the area. The institutional fragmentation implies that most maps are limited by the regional boundaries, making it difficult to frame and even to conceive the Sonian City as a geographic entity, and thus as an object of policy intervention. In this context, designing maps and conducting geographic analysis that deconstruct and reconstruct ecosystemic, functional and administrative boundaries can be helpful to "think" the Sonian City, activate the existing knowledge, and then to devise adequate intervention.