Creating a green network

Among their tasks, the regions and municipalities are responsible for managing green areas. This involves maintaining and restoring existing green areas, creating new ones and managing their distribution throughout the territory to create what is known as a “green network”. Green areas in an urban environment play an essential role in terms of ecology (improvement of urban climate, buffer effect against air pollution, maintenance of biodiversity, hydrologic role), planning (aeration of a very dense fabric of urbanisation), recreation and education. However, monitoring land use is a laborious and painstaking task that makes heavy demands on time and energy. Moreover, the municipalities often lack the kind of detailed and up-todate maps of green areas that they have of the urban network or of built-up areas. This is why the techniques of Earth observation by satellite, and in particular the use of very high resolution images, are so promising in developing applications of use in studying green areas in an urban environment. This applied research was carried out by three scientifi c teams in partnership with a private company seeking to develop products with a high added value. Researchers worked closely with the managing authorities in the fi eld, that are the City of Ghent and the Brussels Institute for Environmental Management, the latter responsible for managing green areas in the Belgian capital.

The first part of the project involved identifying the needs of potential users on the basis of an in-depth and systematic survey. This gave rise to four lines of research. First of all, compiling an inventory of all green areas, whether public or private (most inventories fail to take account of private zones despite their importance to a green network). Subsequently, for each of these identifi ed green areas, compiling details of vegetation zones such as broad-leaved trees, conifers, shrubs, lawns, cultivated areas, etc. Thirdly, detecting changes, whether in terms of the creation or loss of green areas. Finally, making an inventory of the health of individual trees standing in the city streets. On the basis of the Ghent and Brussels pilot projects, the fi rst three lines of research have already produced excellent results in the form of product prototypes complete with automated procedures to facilitate everyday use.