Heathlands are important habitats of the Atlantic region of Europe. In the past several million ha's were available. Today only some 350 000 ha remain, of which about 13 000 ha in Flanders Many of the heathland areas are fragmented. In many studies on heathlands only attention is paid to internal effects, e.g. the effects of nitrogen deposition, restoration of heathland communities, seed banks under heathland or former heath land. On the impact of the surrounding landscape, dispersal or spatial characteristics few research results are available. This work aims at assessing the impact of these spatial aspects (incl. former development) on the biodiversity (mainly plant species) of heathlands.