The goal of a suitability model is to identify the best locations for the thing you are modeling—in your case, the best bobcat patches. To maintain genetic diversity and to allow for movement between the different populations, the patches need to be connected with the best network of wildlife corridors.
In this lesson you will identify the best five patches for the bobcat which will be derived from the final suitability surface created in Lesson 3: Weighting and combining data and you will then connect the patches with the optimum network of wildlife corridors.
This lesson is divided into four sections:
- Opening and editing the ModelBuilder model
- Using the Locate Regions tool to identify regions
- Using the Raster Calculator tool to combine regions into one layer
- Using the Cost Connectivity tool to connect regions with an optimum network
ArcGIS Spatial Analyst is required for this analysis and you must ensure that it is enabled. See Enabling the Spatial Analyst extension.
This lesson continues on the data that you downloaded in lesson 1. If you have not downloaded the data, see the first section in Lesson 1: Exploring and deriving data.
Opening and editing the ModelBuilder model
- If the Suitability Modeling map document was closed after lesson 3, reopen it by double-clicking the SuitabilityModeling.aprx file in the SuitabilityModeling folder.
- Open the SuitabilityModel that you began building in lessons 1, 2, and 3 by right-clicking the model and clicking Edit.
Using the Locate Regions tool to identify regions
The Locate Regions tool will be used to identify the optimal arrangement of habitat patches from the suitability surface.
- Open ArcGIS toolboxes on the ModelBuilder tab by clicking the Tools icon in the taskbar at the top of the map document.
- Click Toolboxes at the top of the Geoprocessing pane. Browse to the Locate Regions tool by clicking the Spatial Analyst Tools toolbox and the Overlay toolset within it.
- Drag the Locate Regions tool into the SuitabilityModel model and place it to the right of the FinalSuitability layer.
- Click the Map tab to view the map document. An existing region will be considered when the new regions are located. From the Project pane, drag the ExistingRegion layer (in the Data.gdb geodatabase) into the Contents pane. Display the ExistingRegion layer on top of the FinalSuitability layer.
- After you have viewed the existing region's location relative to the study area, click on the SuitabilityModel tab. Drag the ExistingRegion layer into the SuitabilityModel model and place it above the FinalSuitability layer.
- Double-click the Locate Regions tool icon in the SuitabilityModel model to open the tool's dialog box. Enter the suitability surface by choosing FinalSuitability:2 from the Input raster parameter drop-down list. Type NewRegions in the Output raster parameter. This file is automatically saved into the Output.gdb geodatabase. To summarize the parameters of the Locate Regions tool, specify the parameters as follows:
- Input raster: FinalSuitability:2
- Total area: 50
- Area units: Square miles
- Output raster: NewRegions
- Number of regions: 5
- Region shape: Circle
- Shape/Utility tradeoff (%): 50
- Evaluation method: Highest average value
- Region minimum area: 5
- Region maximum area: 14
- Minimum distance between regions: 4
- Maximum distance between regions: 13
- Distance units: Miles
- Input raster of feature of existing regions: ExistingRegion:2
ExistingRegion:2 is the ModelBuilder model variable for the ExistingRegion layer and will appear as ExistingRegion:1 in the dialog box.
- Click OK to apply the changes and close the Locate Regions tool's dialog box.
- Right-click the Locate Regions tool and click Run to execute the tool.
- Right-click the output NewRegions layer (green) and click Add To Display to add the output NewRegions layer to the map document.
- Click the Map tab to view the map document. Change the symbology of the NewRegions layer by clicking the Symbology icon on the Appearance tab on the taskbar.
- Choose a Unique Values symbology for the Value field. Choose a varied color scheme from the Color scheme drop-down list to make each region a unique color. Change the color of the 0 (zero) value to No color by clicking the colored square in the Symbol column next to the value 0. Choose No color from the pane that opens.
- In the Contents pane, drag the ExistingRegion layer above the NewRegions layer to view the new regions relative to the existing region.
Using the Raster Calculator tool to combine regions into one layer
Before the new and existing regions can be connected by an optimum, least-cost network, they need to be put into a single layer. In this section, you will use the Raster Calculator tool to merge the ExistingRegion layer with the NewRegions layer to create a single layer of all the regions—all the patches that will be available to the bobcats.
The ExistingRegion layer has a value of 1 for cells in the existing region and NoData everywhere else. If you add the existing regions to the new regions, any locations that are assigned NoData in ExistingRegion will receive NoData in the merged output. Since you want to union the two datasets, you need to change the NoData cell locations in ExistingRegion to 0. Then the two rasters can be successfully added together.
- To reclassify the NoData values in the ExistingRegion layer, open the Geoprocessing pane on the ModelBuilder tab by clicking the Tools icon in the taskbar at the top of the map document.
- Browse to the Reclassify tool by clicking the Spatial Analyst Tools toolbox and then click the Reclass toolset within it.
- Drag the Reclassify tool into the SuitabilityModel model and place it to the right of the ExistingRegion layer.
- Double-click the Reclassify tool icon in the SuitabilityModel model to open the tool's dialog box. Choose ExistingRegion:2 from the Input raster parameter drop-down list (ExistingRegion:2 is the ModelBuilder model variable for the ExistingRegion layer and will appear as ExistingRegion:1 in the dialog box). Type ExistingRegion_new in the Output raster parameter to name the output raster of reclassified values. Enter the following new values in the table provided on the Reclassify tool's dialog box.
Old values New values 1
6
NoData
0
Each of the regions in NewRegions is uniquely numbered from 1 to 5, with all other cells assigned 0. In this step you are reclassifying the 1 values (the existing region) in ExistingRegion to 6, and all other locations, the NoData values, to 0. When you later add the two layers you will get values 1 through 6 for the existing and new regions, with all locations with no patches being assigned 0.
To summarize the parameters for the Reclassify tool, specify the parameters as follows:
Input raster: ExistingRegion:1
Reclass field: Value
Output raster: ExistingRegion_new
- Click OK to apply the changes and close the Reclassify tool's dialog box.
- Once the dialog box is closed, right-click the Reclassify tool and click Run to execute the tool.
- Add the output ExistingRegion_new layer to the map document by right-clicking the green ExistingRegion_new layer in the model and clicking Add To Display.
- Click the Map tab to view the map document. The color scheme clearly displays that the Reclassify tool transformed the existing patch locations to 6 and all the NoData cells to a value of zero.
This reclassification allows you to now add the existing and new regions together to identify all patches available to the bobcats. To do so, you will use the Raster Calculator tool. The Raster Calculator tool will be used to create a mathematical expression allowing you to add the existing region and new regions, resulting in a single layer of bobcat patches.
- In the Geoprocessing pane, browse to the Raster Calculator tool by clicking the Spatial Analyst Tools toolbox and the Map Algebra toolset within it.
- Drag the Raster Calculator tool into the SuitabilityModel model and place it to the right of the NewRegions output layer.
- Double-click the Raster Calculator tool icon in the SuitabilityModel to open the tool's dialog box. Enter the following expression, which combines the ExistingRegion_new and NewRegions layers into a single layer. Within the expression, once the two layers are combined (using the + operator), the expression then sets all zero values (where there are neither existing nor new patches) to NoData. Use the following expression in the Raster Calculator:
SetNull(("%ExistingRegion_new%" + "%NewRegions%"), "%NewRegions%", "Value = 0")Type Regions in the Output raster parameter to name the output raster of available bobcat patches.
- Click OK to apply the map algebra expression and close the Raster Calculator tool's dialog box.
- Once the dialog box is closed, right-click the Reclassify tool and click Run to execute the tool.
- Add the output Regions layer to the map document by right-clicking the green Regions layer in the model and clicking Add To Display.
- Click the Map tab to view the map document. Turn off all other layers in the Contents pane except the FinalSuitability layer. Each region has a unique value, and they are now ready to be connected.
Using the Cost Connectivity tool to connect regions with an optimum network
At this stage of the workflow, the optimum spatial arrangement of regions has been found. Now you will connect the regions with a network of optimum paths using the Cost Connectivity tool. The Cost Connectivity tool requires two inputs: the regions to be connected and a cost surface. A cost surface identifies how costly it is to move across a landscape. For more information on cost surfaces, see the Understanding cost distance analysis case study.
- In the Geoprocessing pane, add the CostSurface layer to the Contents pane from the Data.gdb geodatabase within the SuitabilityModeling folder.
- Visually explore the cost surface by clicking it in different locations. According to the legend, darker areas are less costly and easier for travel, whereas white areas are costly to travel through.
- Add the CostSurface layer to the SuitabilityModel model by clicking the SuitabilityModel tab. Drag the Cost Surface layer into the model and place it above the Regions layer.
- Now that both required inputs for the Cost Connectivity tool are in the SuitabilityModel model, the Cost Connectivity tool can be added. Open the Geoprocessing pane on the ModelBuilder tab by clicking the Tools icon in the taskbar at the top of the map document.
- In the Geoprocessing pane that contains the toolboxes, browse to the Cost Connectivity tool by clicking the Spatial Analyst Tools toolbox and the Distance toolset within it.
- Drag the Cost Connectivity tool into the SuitabilityModeling model and place it to the right of the Regions layer.
- Double-click the Cost Connectivity tool icon in the SuitabilityModel model to open the tool's dialog box. From the drop-down list under the Input raster or feature region data parameter, choose the Regions:2 layer. From the drop-down list under the Input cost raster parameter, choose the CostSurface:2 layer (CostSurface:2 is theModelBuilder model variable for the CostSurface layer and will appear as CostSurface:1 in the dialog box). Type OptimumNetwork into the Output feature class parameter. To summarize the parameters of the Cost Connectivity tool, specify the parameters as follows:
- Input raster or feature region data: Regions:2
- Input cost raster: CostSurface:1
- Output feature class: OptimumNetwork
- Click OK to apply the changes and close the Cost Connectivity tool's dialog box.
- Right-click the Cost Connectivity tool and click Run to execute the tool.
- Right-click the output OptimumNetwork layer (green) and click Add To Display to add the output optimum network to the map document.
- Save the SuitabilityModel model by clicking the Save button on the ModelBuilder tab. Click the Map tab to browse away from the SuitabilityModel model after the model has been saved.
- Order the layers in the Contents pane so that the OptimumNetwork layer is on top of the Regions and CostSurface layers.
- Explore the OptimumNetwork layer by clicking the individual paths. Visible in the attributes are the total cost of the path (PATHCOST) and the source and destination regions.
- Save the map document by clicking the Save button in the taskbar.
Congratulations! You have successfully created a network of wildlife corridors that connect an optimal arrangement of wildlife patches.