Accessible Habitat: the amount of habitat that can be reached without crossing a linear barrier

Hypothetical landscapes illustrating accessible habitat. In A, all habitat (dark grey) is accessible by some species from a focal sampling point (small black circle) without crossing a linear barrier such as a road (thick black line). In B, C and D accessible habitat (dark grey) is less than total habitat (light grey + dark grey).  Distance to the nearest road is the same in landscapes B, C and D, but accessible habitat is lower in landscapes C and D. Road density is higher in landscape D than in landscape C but accessible habitat remains the same in both landscapes.
Eigenbrod et al.pdf A .pdf file of the paper describing the accessible habitat concept:”Accessible habitat: an improved measure of the effects of habitat loss and roads on wildlife populations’ Felix Eigenbrod, Stephen J. Hecnar, and Lenore Fahrig. (2008) Landscape Ecology 23 : 159-168.

The original publication can be found at

Instructions (MS Word) A detailed description of the accessible habitat tool and instructions for its use. A .zip file containing the ArcGIS tools (one for ArcGIS 9.0/9.1; one for ArcGIS 9.2) for calculating accessible habitat, the Python code for these tools, documentation, and the accessible habitat paper.

The Accessible Habitat 9.1 tool works for ArcGIS 9.0, ArcGIS 9.1. The Accessible Habitat Tool 9.2 works for ArcGIS 9.2, and may also run on newer versions of ArcGIS. Please contact the author ( if you have any problems with the tool.