This map layer is a grid map of the conterminous United States, created
from National Land Cover Data (NLCD). The NLCD data was reclassified into
four categories: forest, other natural (e.g. grassland, wetland, etc.),
human land use (e.g. agriculture, urban, etc.), and nodata (water, ice and
snow, and bare rock/sand). A 9 x 9-pixel moving window was then used to
generate forest edge measurements for every pixel, regardless of its
class.
Within each window, the edges of all forest pixels were examined to
determine what type of land cover shared each edge. Three new grids were
created, one for each edge type (forest-forest, forest-natural, and
forest-human). The values in these grids were calculated as the number of
edges with the appropriate type in the window divided by the total number
of forest edges, regardless of neighbor. These grids represented forest
connectivity (forest-forest edges), naturally caused forest fragmentation
(forest-natural edges), and human caused forest fragmentation (forest-
human edges). In the map, forest connectivity is displayed in green,
natural fragmentation in blue, and human fragmentation in red. Yellow
indicates areas that are an approximately equal mix of connected forest
and human fragmentation, while cyan indicates areas that are an
approximately equal mix of connected forest and natural fragmentation.
Black represents areas with no forest in the 9 x 9-pixel window; white
represents ignored or nodata areas, such as water, ice and snow, and bare
rock/sand.
The data available through the National Atlas of the United States are
in GeoTIFF format.
