Least-cost corridors classified as well-connected (≤15km) based on cost-weighted distance - A landscape connectivity analysis for the coastal marten (Martes caurina humboldtensis)

This dataset contains an alternative representation of the least-cost corridors produced by our habitat connectivity model for the coastal marten, where a Maximum Cost-Weighted Corridor Distance parameter of 15km has been set (i.e. corridors with a cost-weighted distance greater than 15km have been excluded). This single parameter change was the only difference between the output from this model run, and the output from our Primary Model. This dataset was used in our report to make maps depicting corridors that are well-connected (≤15km), moderately-connected (≤45km), or poorly connected (>45km; i.e. all remaining corridors in the Primary Model that didn't fall into the first two categories) based on cost-weighted distance. To construct these figures, you need two or three of the aforementioned datasets layered on top of one another. See Figures 14, A6.3, and A6.4 in the report for symbology examples.

After developing the coastal marten landscape resistance surface (i.e. movement model) and mapping habitat cores, we used Linkage Mapper to identify Least-Cost Paths (LCPs) between cores and to map broader mosaicked corridors around these single-pixel width paths. Linkage Mapper proceeds through several steps to complete these tasks (McRae and Kavanagh 2016). First, it identifies and lists which habitat cores are nearest neighbors using both the Euclidean distance (the “as-the-crow-flies” straight-line distance between nearest points on the edges of a pair of cores regardless of the character of the intervening landscape) and the cost-weighted distance (CWD). Second, it creates a “stick map” using straight-line linkages to connect core area pairs that are candidates for corridor mapping. Third, it locates the LCPs through the resistance surface between these pairs of cores and calculates their cost-weighted distance. This LCP is a single 30m pixel wide. A single pixel’s cost-weighted distance is the cell’s resistance value multiplied by the size of the cell, and the cost-weighted distance of an LCP is the sum of the cost-weighted distances of the pixels it runs through.

Finally, Linkage Mapper creates least-cost corridors, which are wider swathes surrounding the LCPs that have only slightly higher movement costs and are more biologically realistic for conservation planning. It does this by calculating for each pixel on the landscape how much more costly a pathway passing through it between two cores would be than the LCP. Pixels closest to the LCP tend to be relatively close to it in CWD value, with the potential contribution of pixels to connectivity tending to decrease further away from the LCP. Linkage Mapper then creates a composite linkage map by assigning each pixel its minimum value relative to the nearest LCP (WHCWG 2010). Thus, the final map is a mosaic of normalized least-cost corridors around the LCPs. These corridors will vary in width depending on the resistance values surrounding the LCP.

We opted not to set a maximum Euclidean or cost-weighted distance for least-cost corridors between habitat cores in our primary model, but we did impose a 15km Maximum Cost-Weighted Corridor Distance parameter for this alternative model run. 

This is an abbreviated and incomplete description of the dataset.  Please refer to the spatial metadata for a more thorough description of the methods used to produce this dataset, and a discussion of any assumptions or caveats that should be taken into consideration.

Tags: coastal-marten, connectivity-modeling, general-biology-at-risk-biota-te-species, general-biology-species-mammals, general-landscapes-landscape-dynamics, general-landscapes-landscape-ecology, general-management-habitat-management-habitat-models, general-management-landscape-management-landscape-connectivity, gnarly-landscape-utilities, humboldt-coastal-marten, humboldt-marten, least-cost-path-analysis, linkage-mapper, martes-caurina-humboldtensis, pacific-marten
Organization: Department of the Interior