Composite spatial indexing of regional habitat importance

Indexing and mapping of co-occurrence for multiple species is central to many analyses of conservation needs, ecosystem health, and community composition. Species richness is often used because of its simplicity and interpretability, but a variety of ecologically based weighting schemes for species have been developed for special purposes such as determining biotic integrity. This work is concerned with indexing a balance between common and uncommon species for preliminary assessments of conservation needs. A Regional Habitat Importance Index is constructed in a manner that provides joint ordering of species and landscapes. The index lends emphasis to species having a scarcity of habitat over a region, low representation in conservation areas, and shortage of opportunity for expanding protection. Application of the index is illustrated for mammals and birds in the context of GAP Analysis for the state of Pennsylvania, USA.