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In the present study, existing records were used. (For Gairloch, see 
McVean and Ratcliffe, 1962 and Birks, 1973. For Merseyside, see 
South West Lancashire Data Bank, Sefton District). 
Vertical Structure 
This information can be deduced from knowledge of the habitat type, e.g. 
woodland contains four vertical layers, comprising ground, field, shrub 
and tree layers. 
Local Scarcity 
Owing to the lack of records, scarcity of habitat type can only be estimated 
locally, over the study area. The total extent of each habitat type was 
calculated and the inverse was taken, to represent an index of Local 
Scarcity for each habitat. 
Inter- and Intra-Habitat Diversity 
  
Inter-habitat diversity was easily obtained by counting the number of 
habitats in each grid square. Intra-habitat diversity, representing a 
variety of terrain features such as rock outcrops, coast length, streams 
and hedgerows, could be interpreted and measured from aerial photographs. 
Relative relief was derived from Ordnance Survey, 1:10.000 map contours.