Habitat suitability modelling for calcareous grassland restoration on the South Downs, United Kingdom.

The South Downs Area of Outstanding Natural Beauty, UK, is an internationally and nationally important landscape, which contains a significant proportion (28%) of the southeast of England's 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 steeper slopes. The re-creation and restoration of these species rich grasslands has become a central aim of national and regional conservation organisations, however, the methods and mechanism by which restoration sites could be identified has not been clarified. The purpose of this work was to study the landscape characteristics of the calcareous grassland systems, and by use of GIS-based modelling approaches identify those sites on the downland most suited to the re-establishment and expansion of calcareous grasslands. Using a weighted scoring approach, 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 sites for targeted restoration. The approach models the relationship between specific grassland communities and topographic variables, 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.