This map package contains four resistance surfaces, one which is the same surface at two different resolutions (30m and 90m). The resistance surfaces were used in Linkage Mapper and Omniscape to model naturalness connectivity in Southwest Washington. Naturalness resistance values from all the inputs can be found in the report methodology.
We made three different resistance surfaces, using the data inputs, found here, for testing in sensitivity analyses. For the first, we started with a conventional methodology for creating resistance surfaces (Using Gnarly Landscape Utilities), and then combined this result with nuanced layers about road impacts and building density impacts. These nuanced layers have continuous numerical values for resistance, as opposed to the conventional, small number of discrete values. This methodology is overviewed in the report, and yields the Basic Resistance surface. We then utilized data about the location and quality of wildlife crossings under Interstate 5. This is the Standard Resistance Surface. We then incorporated protected area status. For example, those areas that were Wilderness (i.e. GAP status 1) were given a lower resistance to those areas that were private land, all else being equal. This yielded the Resistance Surface with Protected Area Benefits. This method is summarized in a figure in the supplementary information, and detailed herein.
Creation of Landscape Resistance Basemap:Used Gnarly Tools Resistance Calculator (McRae et al. 2013) to create a base landscape resistance layer. Inputs into Gnarly Tools Resistance Calculator:Input raster layers: Land Use, Roads, Transmission lines with buffer, Natural Gas Pipeline, Trails, Wind Turbines with buffer, NHD Flowlines, Railroads with bufferResistance scores based off Columbia Plateau values for landscape integrity, found in Appendix C of the Washington Connected Landscapes Project: Analysis of the Columbia Plateau Ecoregion document (WHCWG 2012), with modifications. See full spreadsheet for values and notes about the modifications (This could eventually be Appendix A, but for now is unformatted and is linked here).Expanded roads by 1 to avoid “kitty-corner” issues.Combined inputs using MAXDid not check box to add 1 to resistance since none of our values were 0.
Step 2 Resistance Surface: Resistance Basemap and Road Buffer GradientsThe Resistance Basemap was overlaid with the Road Buffer Gradients, we used cell statistics to take the max value from each raster.Basic Resistance Surface without I5 Crossings: Step 2 Resistance Surface and Building Footprint Impact GradientsThe Basic Resistance Surface was created by overlaying the Step 2 Resistance Surface and the Building Footprint Impact Gradients using cell statistics to take the max value from each raster.
Standard Resistance Surface: Basic Resistance Surface with Interstate 5 CrossingsThe Standard Resistance Surface was created using cell statistics to take the minimum value of the Basic Resistance Surface and the Interstate 5 Crossings Overlay layer. This overlay was done last to prevent any of the max overlays from overwriting the lower resistance value of the crossing locations. (Geoprocessing tip: The final overlay layer has values of 2,000 for all cells in the study area that are not within the crossings, and each crossing has its own resistance values. The value of 2,000 was used since it is larger than all of the resistance values so it won’t overwrite any other values when combined with the Basic Resistance Surface. )
Resistance With Protected Area Benefits: The Standard Resistance Layer multiplied by Protected Area Type.
“Version 2.0” (i.e. v190215.1)
We used the new resistance surface that has 1 as the lowest value. We made two reclassified rasters of the protected areas database, PA Product, and PA Sum, to be combined with the resistance surface using a product, and a sum, respectively. Product disproportionately affects high resistance cells when combined with the resistance surface, and Sum disproportionately affects the low resistance cells. These were both used and combined.
We multiplied the Standard Resistance layer by the PA_Product raster layer, then added the PA_Sum layer. Hence, an original resistance cell valued at 1 on Gap Status 1 land stayed a value of 1, and in unprotected land became a value of 12. And, a cell valued at 1000 stayed at 1000 in Gap Status 1 lands (if such a place exists), and became 2010 in unprotected lands. This became the “Resistance with Protected Area Benefits” layer (v190215_1).
