News and views on wildlife corridors, linkages, and connectivity
on Apr 11 2011
Brad McRae and Darren Kavanagh from The Nature Conservancy's Washington chapter recently released Linkage Mapper, a GIS tool designed to support regional wildlife habitat connectivity analyses. Linkage Mapper is an ArcGIS toolbox developed for the Washington Connected Landscapes Project, and is available for free to use on similar projects.
Linkage Mapper is a GIS tool designed to support regional wildlife habitat connectivity analyses. It consists of several Python scripts, packaged as an ArcGIS toolbox, that automate mapping of wildlife habitat corridors. We developed these scripts for the Washington Wildlife Habitat Connectivity Working Group’s (WHCWG) 2010 statewide connectivity analysis, and are making them public for use in other wildlife connectivity assessments.
Linkage Mapper uses GIS maps of core habitat areas and resistances to identify and map linkages between core areas. Each cell in a resistance map is attributed with a value reflecting the energetic cost, difficulty, or mortality risk of moving across that cell. Resistance values are typically determined by cell characteristics, such as land cover or housing density, combined with species-specific landscape resistance models. As animals move away from specific core areas, cost-weighted distance analyses produce maps of total movement resistance accumulated.
The scripts use ArcGIS and Numpy (numerical Python) functions to identify adjacent (neighboring) core areas and create maps of least-cost corridors between them. The scripts then normalize and mosaic the individual corridor maps to create a single composite corridor map. The result shows the relative value of each grid cell in providing connectivity between core areas, allowing users to identify which routes encounter more or fewer features that facilitate or impede movement between core areas.