Large Forest Blocks

The Indicator

Large forest blocks are becoming increasingly rare in Maryland as urban development consumes ever increasing amounts of open land. Since large blocks of forest offer critical habitat, it is important to keep as many of them as possible. Very large forest blocks are major components of the State’s green infrastructure. They are clearly more prevalent in Western Maryland, the Lower Eastern Shore and Southern Maryland than in the Baltimore-Washington metropolitan corridor or the heavily agricultural areas of the Eastern Shore. As Southern Maryland continues to experience a development boom, losses of large blocks of forest may be anticipated in this region.

This grid was created from the National Land Cover Data set (NLCD) to display forest land greater than 50 acres, as part of a Forest Interior Dwelling Species (FIDS) habitat assessment. Forest tract size, as portrayed in the map, is based on the total contiguous forest area regardless of property boundaries. Two forest tracts are considered noncontiguous or disjunct if separated by at least 30 feet of nonforested habitat (e.g., road, transmission line right-of-way, cropland, etc.), about the typical width of a 2-lane, paved county road.

Indicator Use

Large forest blocks have greater potential than smaller ones to contain sufficient interior forest–defined as forested land cover at least 300 feet from differing land cover or from primary, secondary, or county roads–to provide habitat for a variety of species requiring such conditions. Forest blocks at the lower limits of the definition of large are the most likely to be found in urbanized areas and present an important opportunity to maintain biological diversity, and the aesthetic values of forests, in these areas.

Ecological Assessment | Criterion 1 | Data & Indicators | Home