Corridor Analysis and Least Cost Path

The second map I've produced for Application in GIS is a corridor analysis of potential black bear movement between two protected areas of Coronado National Forest.  This sort of analysis is useful for conservation efforts so environmentalists and park rangers can have some idea where black bears are most likely to be encountered.

For the creation of this corridor I took into account three factors: distance from roads (bears prefer to be farther away), elevation (bears have a preference for elevations 1,200 to 2,000 meters), and land cover (certain types of land are more suitable to black bears).  For the road distance, I took the roads shapefile and used the euclidean distance tool.  From there I reclassed the distances appropriately to create a new raster.  I also used the reclassify tool on the elevation and land cover raster to take into account suitability.

Then, I combined these rasters using the weighted overlay tool.  I gave a weight of 60% to land cover and 20% to the two remaining rasters.  This creates a raster that shows the general suitability of an area for a black bear.

For the creation of a least cost raster, I used the reclassify tool to invert the values.  The new values, or the cost surface, where calculated by 10 minus the suitability score.  After that it was necessary to create two cost distance rasters.  The least cost surface raster was combined two separate times.  Finally, these two cost distance rasters are combined using the corridor tool to create the desired corridor output.

The darker the red the more likely a black bear is to travel within that area when going between the two protected forested zones.

The next step in getting the map ready for production is to determined the desired extent of the corridor.  I did this by finding the lowest overall value in the corridor and multiplying that by 1.1, 1.2, and 1.3 for each of the red bands where the bears are the most likely to travel.

With this map it is much easier for the park rangers to know where the bears are likely to travel, especially in areas near to roads.  They can put up signage or other warnings to alert travels that they are more likely to see a bear there.  Or they could try to petition for changes such as a wildlife bridge which serves to keep both people and animals safer.