A Note on Creating Robust Resistance Surfaces for Computing Functional Landscape Connectivity

Increasingly, conservation scientists are using geographical information systems (GIS) and, in particular, cost-weighted methods to compute metrics of landscape connectivity. Rothley (2005) raised an important technical issue that scientists need to be aware of when using these methods. Costweighted methods are used to compute the connectivity of a surface, a raster, by specifying the cost of traveling across a landscape using a surface of cost-weights. This surface is often called the friction or resistance surface (Knaapen et al. 1992) or its inverse, the permeability surface (Singleton et al. 2002). In GIS literature, this general method has been typically called cost-weighted distance and least-cost path analysis (Eastman 1989, Berry 1993, Douglas 1994, reviewed in Theobald 2005b).