Ecological management of the Sussex South Downs : applications of GIS and landscape ecology.
The South Downs Area of Outstanding Natural Beauty is a nationally important
conservation area, which contains a significant proportion (28%) of the South East
calcareous grassland resource. The traditional calcareous grassland habitats
characteristic of the Downland landscape have suffered significant losses since the
Second World War, and the remaining sites are small, fragmented and confined to the
more marginal areas, often the steeper slopes. The recreation and regeneration of these
species-rich grasslands has become an important aim of regional conservation
organisations, but the methods and mechanisms by which restoration sites could be
identified has not been clarified. The work reported here aims, by the integration of
landscape ecology and Geographical Information Systems, to develop a sound
methodological approach for the targeting of sites for restoration and regeneration of
calcareous grassland on the South Downs.
The study examines temporal land use dynamics of the Downland and the
predominant land conversion sequences are identified. Land management changes
between 1971 and 1991 are assessed, and sites of unimproved grassland and those
sites considered more marginal to modem intensive farming approaches are identified.
The structure of the Downs landscape is investigated at the landscape, habitat and
community level using fine-scale spatial data. Particular emphasis is placed upon the
remaining calcareous resource and the extent of habitat loss and fragmentation is
quantified. Analysis at the community level shows a clear relationship between
community richness and habitat area. The analysis identifies key attributes of
calcareous grassland sites and provides a baseline from which to formulate restoration
targets and objectives.
Finally, using fuzzy logic, a GIS-based Habitat Suitability Model is developed for use
as a tool to support strategic landscape evaluation and to provide a method of
identifying areas of search and site selection for targeted restoration. The approach
models the relationships between specific grassland communities and landscape
position, and is applied to the South Downs landscape in order to predict the nature of
grassland communities likely to result from restoration efforts at specific sites.