AERIAL PHOTOGRAPHY AND GIS TO QUANTIFY HABITAT SUCCESSION IN ECOLOGICALLY SIGNIFICANT COASTAL DUNES OF SOUTH WALES, UKS. SanjeeviAbstract This paper presents an attempt to measure the path of habitat and vegetation succession in a coastal dune system (Kenfig National Nature Reserve, south Wales, UK) using remote sensing and GIS. The loss of 'slack' habitats associated with the continuing stabilization of this dune system is a major cause for concern. These habitats support a range of plant species, including the rare fen orchid, Liporis loeselii, and other hydrophytes. A decrease in their areal extent implies a reduction in biodiversity. To quantify the overall rate and spatial dimension of these changes, a series of aerial photographs dating from 1962 to 1994 were digitally scanned and analysed in an image processing system. The resultant maps, transferred to a vector-based GIS, were used to derive a transition matrix for the dune system over this period of time. The results indicate that there has been a marked reduction in the total area of bare sand (19.6% of the dune system in 1962, but only 1.48% 1994) and a decline in both the areal extent and the number of dune slacks. Analysis of the habitat maps and hydrological data within the GIS analysis suggests that even dry slacks have the potential for further 'greening' and to support invasive species. In terms of habitat management, however, there is still scope to restore many of the slacks to their original state. It is estimated that at least 24% of the area occupied by partially and moderately vegetated slacks could be rehabilitated.
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