Fragmentation in habitat maps produced by the EFM process is generated by land surface topography that affect the connectedness of aquatic habitats through human or natural features, splicing of multiple layers into a habitat mosaic, and application of habitat suitability criteria that split otherwise connected areas into smaller pieces surrounded by areas with zero suitability. 

In GIS, raster datasets are grids of continuous cells organized in rows and columns.  Areas with raster values can be separated by areas of no data.  Connected raster cells that provide habitat are herein called “chunks” (Figure 19). 

Figure 19.  Illustration of a habitat map.  Separate pieces of habitat are referred to as “chunks”.


The GeoEFM Patches toolset includes two connectivity methods.  The physical connectivity method has options for identifying chunks based on connected edge or connected point.  The buffer method includes cells in chunks based on connected points. 

Chunks separated by less than or equal to twice the buffer radius (in the buffer method) are grouped into “neighborhoods” (Figure 20).  If a chunk is separated by more than the threshold distance in all directions, it is placed in its own neighborhood.  Neighborhoods are not used for the physical connectivity method because that method assumes chunks that are physically disconnected do not interact ecologically.

Figure 20.  Chunks with areas greater than or equal to the minimum chunk area (user specified and optional) and that are spaced tightly enough to act together ecologically are grouped into “neighborhoods”.


Each neighborhood is assessed separately to split habitat into “patches”, each of which would be a unit of ecological importance such as the amount of habitat needed to support an individual, or habitat for a pack of individuals, or habitat for a nesting site.  Being in a neighborhood does not indicate whether there is enough habitat to create a patch, it simply means that the collection of chunks are spaced tightly enough to act together to potentially support one or more patches. 

Currently, connectivity can be assessed only for raster datasets. 

The Patches toolset has two tools.  The first is called Create Patches - Buffer Method.  The second is called Create Patches - Physical Method.  Tools can be started via a double-left-click or via the right-click Open menu option.