Learie Miller

The Toronto Region and Conservation Authority (TRCA) has adopted the Terrestrial Natural Heritage Program to address terrestrial biodiversity loss. The program considers terrestrial biodiversity at the landscape, vegetation community and species level. At the landscape level a scoring and ranking system using Geographic Information System (GIS) is used to identify habitat patches, and to evaluate parameters such as habitat size, shape, and matrix influence. This results in the computation of a total score which allows one to evaluate and monitor the status of habitats and (indirectly) species. It is suggested that the methodology to compute total score would be applicable at varying scales such as the municipal, sub-watershed and watershed levels.

In this study, total scores were computed for the Centreville Creek sub-watershed to test the applicability of the methodology to a small area, and compared with results generated for the overall TRCA jurisdiction. The results for Centreville Creek sub-watershed were generally comparable to those obtained for the TRCA jurisdiction, with most of the patches receiving a 'fair' total score based on the classification scheme used for landscape analysis. Given the fact that the area was considered to be in good condition from an ecological perspective, the total scores were (disappointingly) much lower than initially anticipated. The habitat patch scores were adversely affected by their shape scores as many of the patches were irregular in shape and fragmented. Conversely, better results were obtained for large patches, confirming the importance of size in landscape patch analysis. Georeferenced information on flora and fauna superimposed on habitat patch information can provide improved insight as to the species associated with specific patches. Ultimately this information could be used to identify areas that should be prioritized for conservation and restoration efforts.