Forest Fragmentation Risk, Contiguous US

This map layer is extracted from a grid map of North America including the Caribbean
and most of Mexico. The map layer is an excerpt from a global assessment of forest
fragmentation (Riitters et al., 2000). Each pixel value represents an index of forest
fragmentation for the surrounding 81 sq. km.

The map layer was created by applying spatial algorithms to a 1 sq. km.
resolution map of global land cover (Loveland and Belward 1997) known as
NAIGBP1_2L, obtained from the USGS Center for EROS Distributed Active
Archive Center (DAAC) as part of the Global Land Cover Characteristics
database (GLCC)(Loveland et al. 1991, 1999). One of six categories of
fragmentation was identified for each forested pixel in North America
from the amount of forest and its occurrence as adjacent forest pixels
within a 9x9 pixel (81 sq. km.) window surrounding the pixel on the
original land-cover map.

The map layer describes one aspect of forest fragmentation at one scale.
The forest fragmentation index is designed to distinguish among types of
fragmentation (e.g., edges on the interior versus the exterior of a
forest patch) and it also reflects differences in the absolute amount of
forest present. However, no distinction was drawn between "natural" and
"human-caused" fragmentation.

The data available through the National Atlas of the United States are
in GeoTIFF format. This is a revised version of the May 2002 map layer.

This map layer was extracted from the map previously distributed as the Forest
Fragmentation Index Map of North America.