Reserve Coverage and Requirements in Relation to Partitioning and Generalization of Land Classes: Analyses for Western New South Wales

The extent to which existing conservation reserves cover or represent the different land classes in a region depends on the scale at which those land classes are defined. In a previous review of regional studies we could not separate the influence on reserve coverage from aspects of scale of classification or mapping. In this study we measured the influence of three aspects of scale on the coverage of existing reserves and the area of new reserves required to represent all land classes. The aspects of scale we used were agglomerative (bottom-up) partitioning, divisive (top-down) partitioning, and generalization of the polygons representing discrete map units. The analyses were based on two existing classifications of a large region. One of these was originally produced at two scales of divisive partitioning. We modified the second classification to produce wide differences in the two other aspects of scale. For all aspects of scale the results confirm that existing reserves in the region tend to represent more coarse- than fine-scale classes, but this depends on the criteria used to determine when classes are "represented." For all aspects of scale, larger total areas of new reserves are needed to represent fine-scale rather than coarse-scale land classes. This trend holds regardless of the minimum proportional area of each land class to be represented but varies with the size of the sites considered reserves. The results reinforce the scale-dependence of assessments of reserve coverage and establish the scale-dependence of assessments of reserve requirements. They also indicate that comparisons of coverage and requirements between regions or in the same region through time must be standardized for type and scale of classification.