Each run of the ‘Linkage Pathways’ tool from the Linkage Mapper toolbox required a new folder, containing only the resistance GRID and the core habitat shapefile. After manually inputting these two inputs, the main steps of the tool are as follows (McRae & Kavanagh, 2011):
- Identify Adjacent (neighbouring) Core Areas
- Construct a Network of Core Areas
- We chose ‘Connect ALL Core Areas’ as our Network Adjacency Method, as opposed to Euclidean or Cost-Weighted methods
- Calculate Cost-Weighted Distances and Least-Cost Paths
- We unchecked ‘Drop corridors that Intersect Core Areas’
- Prune Network (Optional)
- We did not check this option
- Calculate, Normalize, and Mosaic Corridors
- We also chose to truncate corridors to 200km
The outputs of the tool include vectors as well as raster maps of the corridors. Initially, we worked with only four of the core habitat areas until we had perfected our resistance raster and use of the tool. Using the tool for our entire project area with all core areas resulted in 28 individual corridors and a run time of 4 minutes and 22 seconds. Learning to use the Linkage Mapper tool took a lot of trial and error, but its outputs are truly more elaborate than ArcGIS Pro’s ‘Corridors’ tool (which only produces vector line least-cost paths, Step 3 of this tool) (Figure 6) and we highly recommend it for future projects.
Figure 6. (a) Least-cost paths between core habitat areas, mapped as line vectors. Resistance raster below. (b) Normalized and mosaicked corridors of the Vancouver Island wolf between core habitat areas, with lighter-coloured corridor cells indicating each cell’s relative value of connectivity.