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Abstract
An attempt to understand the problems associated with coastal ecosystems and landscape units for conservation management requires, in the first instance, a well defined/documented map, a resource information system, and change detection techniques. Also, accurate habitat maps are essential pre-requisites to an improved and effective conservation-management programmes. Conventional surveying techniques and in situ measurements clearly have an important role in producing such maps, but they are time-consuming, manpower-intensive and, hence, expensive - particularly in the context of long-term monitoring programmes. For this reason, attention has increasingly been focussed on the use of airborne and satellite remote sensing data, combined with the spatial analytical capabilities of modern Geographical Information System (GIS) technology.

This paper presents an attempt to quantify vegetation and landscape changes in a coastal dune system (Kenfig National Nature Reserve, south Wales, UK) using GIS and airborne remote sensing. 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, Liparis 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.

Introduction
In the general context of coastlines, issues of biodiversity and nature conservation are perhaps most pronounced for dune systems, which form approximately 20% of the area occupied by world's coastal landforms and which are especially rich in species of plants and animals. These features not only make them areas of special research interest, but have also led to some of them being categorized as Protected Areas. The over-stabilization of coastal dunes - often as much a problem as erosion - leads to loss of biodiversity.

An attempt to understand the problems associated with dunal landscape and vegetation succession (and hence loss of biodiversity) for conservation management requires, in the first instance, a well defined/documented map, a resource information system, and change detection techniques. Also, accurate vegetation and habitat maps are essential pre-requisites to an improved understanding of the problems associated with conservation and management programmes. They can form the basis of, and spatial dimension to, resource information systems and change detection techniques. Conventional surveying techniques and in situ measurements clearly have an important role in producing such maps, but they are time-consuming, manpower-intensive and, hence, expensive - particularly in the context of long-term monitoring programmes. For this reason, attention has increasingly been focussed on the use of airborne and satellite remote sensing data, combined with the spatial analytical capabilities of modern Geographical Information System (GIS) technology.

Hartog et. al. (1992), for example, combined aerial photography and GIS to derive transition matrices in a study of the succession of dune vegetation structure resulting from changes in the level of ground-water in the Amsterdam Waterworks dunes. They present ideas as to how these data could be used to analyse spatial patterns on the dune surface and to model landscape succession. Similarly, Davis et al. (1994) provide an account of the use of remotely-sensed images (Landsat-TM data and aerial photographs) and GIS technology to characterise vegetation communities in southwestern California. The authors demonstrate how a vector-based GIS, combined with remotely-sensed data, can be used to produce improved landscape-ecological maps compared to those generated using traditional mapping and manual cartographic procedures.

This paper presents an attempt to measure the path of habitat and vegetation transition in the Kenfig coastal dune system and NNR (National Nature Reserve, south Wales, UK) using remote sensing (sequential aerial photography) and GIS. The loss of 'slack' habitats associated with the continuing stabilization of this dune system has been a major cause for concern among the reserve mangers. These habitats support a range of plant species, including the rare fen orchid, Liparis loeselii, and other hydrophytes. A decrease in their areal extent implies a reduction in biodiversity. Landscape transition ccurring at Kenfig need to be quantified before proceeding to formulate and implement any management plans. Also, identification of the landscape units undergoing change will improve our understanding of the interactions between the geomorphological and biological agents and processes.

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