Step 7: Define and Map Habitat Cores, Corridors and Islands

The main objective of this step is to structure an assessment of landscape connectivity and identify habitat networks common to both existing and proposed conditions so that comparisons can be made during the alternatives analysis phase.

The key objectives include:

  1. To identify the baseline habitat network components; Cores, Corridors , and Islands
  2. To describe or depict the level of connectivity through each habitat network.
  3. To assign a functional score to these features

Using the definitions adopted for the project-specific habitat assessment, the habitat networks are divided into respective cores, corridors and islands. The identification of cores, corridors and islands is directed by the target species and the assumptions which guide the user’s delineation of these features should be documented and accompany any maps or figures.

The functional assessment of cores, corridors and islands is more subjective. The assumptions which guide the user’s delineation of these features, particularly any qualitative scoring of these features, should be explained and accompanied by maps or figures. There are many methods for qualitatively scoring network components, though some  simple metrics are presented here which relate back to basic fragmentation factors: size, shape, and location/configuration (ELI 2006).

Federal and state wildlife agencies may have their own preferred metrics that can be incorporated in to the process. Examples of scoring methods can be reviewed at the following sites:

go to Step 8: Develop GIS Maps of Habitat Linkages