Corridor Analysis: Connecting Fragmented Habitat
This tutorial designs a wildlife corridor between two habitat patches: turn a land-cover map into a friction surface, accumulate travel cost from each patch, and extract the least-cost corridor that connects them. It uses the Raster tools and the Processing toolbox.
1. Load your layers
- a land-cover / land-use raster for the study area,
- two or more habitat patches as polygons (reserves, forest remnants).
If the patches are only drawn by eye, digitize them on the Annotations layer first and export them.
2. Build a friction surface
Movement is not equally easy everywhere: forest is cheap to cross, urban land is nearly impassable.
- Run Processing → Whitebox Toolbox → Raster → Reclass on the land-cover raster.
- Map every class to a friction value on a 1–10 scale: forest 1, grassland 3, cropland 5, roads and built-up 10.
The output is a friction surface where every cell carries the cost of crossing it.
3. Accumulate cost from each patch
Run Processing → Whitebox Toolbox → Raster → Cost Distance twice — once with each habitat patch as the source and the friction surface as the cost input. Each output grid stores the accumulated cost of reaching any cell from that patch.
4. Extract the corridor
Run Processing → Whitebox Toolbox → Raster → Corridor with the two cost-accumulation grids as inputs. The output is low where both patches are cheap to reach — the corridor is the band of low values linking them.
5. Trace the least-cost path
Run Processing → Whitebox Toolbox → Raster → Cost Pathway with a start and end point inside the patches to draw the single optimal route along the corridor floor. This is the line a fence-to-fence acquisition would follow.
6. Style and share
- Clip the corridor to the study area and style it over the land-cover base with a two-color colormap.
- Vectorize the corridor core if you need it as a boundary, and publish the map with Export As HTML.
Next steps
- Cost Allocation splits the landscape between three or more patches when the corridor network is not a simple pair.
- Swap the friction surface for a weighted stack (friction + slope + road density) and rerun — the corridor moves to where crossing is genuinely easiest.