A GIS database of the 1300 active mineral sites (defined as those where working is actively taking place) in England was created by collecting data from 98 Mineral Planning Authorities during 2005. This information on extent of active planning permission, end-use of the site and whether extraction intercepted the water table, supplemented data licensed from the British Geological Survey (BGS).
Four other sets of data were used in the model:
• Soilscapes data licensed from NSRI
• BAP habitat inventories downloaded from English Nature and the RSPB's Heathland Extent and Potential dataset
• Land-use within a 1 km buffer of each of the 1,300 sites: semi-natural habitat digitised from aerial photographs
• Joint Character Areas (JCA) downloaded from English Nature.
Habitat creation experts built up a matrix of ecological parameters defining conditions under which each of 17 priority BAP habitats would be physically possible. The model was built in ArcGIS 9.1 around this matrix of mineral type, soil type, hydrological conditions and broad bio-geographic zones (using JCAs). First, the model used the parameters to find sites where each habitat was physically possible. Some sites had the potential to support more than one priority BAP habitat type. There is therefore some overlap between the areas of habitat that can be created. The model then went on to prioritise sites, based on proximity to existing patches of the same habitat, as shown below:
• Priority 1: mineral site adjacent to existing fragment of the semi-natural habitat
• Priority 2: mineral site within 1 km of existing fragment of the semi-natural habitat
• Priority 3: mineral site within 5 km of existing fragment of the semi-natural habitat
• Physically possible: mineral sites with suitable conditions within broad biogeographic zone of the semi-natural habitat.