OVERVIEW

The Contiguous Natural Lands datalayer was developed for the purpose of identifying large, contiguous tracts of natural land.  "Contiguous" lands were defined using selected roads and a "natural land" definition tailored to meet the objectives of the Massachusetts Resource Identification Project (MRIP). The layer, NATLANDS, is stored in the Watershed library, with each coverage named NATL. In ArcSDE the layer is named NATCONTLANDS_POLY. The identification of contiguous natural lands is listed as a priority for numerous conservation planning efforts.  The Contiguous Natural Lands datalayer represents a coarse filter analysis of these features.  Additional assessment may include: the geometry of these features (area-to-perimeter ratio, core area assessment, etc.), spatial juxtaposition, amount as well as location of  "non-natural" landcover classes within and adjacent to natural lands, and spatial distribution of roads greater than class 5 (unimproved roads, trails) within the contiguous natural lands.  Also note that the contiguous natural lands were delineated only within the Massachusetts state boundary and therefore may under-represent contiguous natural lands that cross state boundaries.

Road features from the Massachusetts Highway Department Roads datalayer with a CLASS less than or equal to 5 were combined with the Trains and Transmission lines datalayers, as well as with the state outline, to create boundaries for contiguous natural land polygons.  Using ARC/INFO, "natural lands" features were selected from the MRLC National Landcover Datalayer with a reselect on the following landcover categories:
 

Landcover Code		Description
11		Open Water
31		Bare Rock/Sand
33		Transitional Bare
41		Deciduous Forest
42		Evergreen Forest
43		Mixed Forest
51		Deciduous Shrubland
81		Hay/Pasture
91		Forested Wetland
92		Emergent Herbaceous Wetland

The selected "natural lands" categories were coded as 1 within a NAT attribute item.  The contiguous boundaries (roads, trains, transmission lines, state boundary) were unioned with the natural landcover features and then a reselect was applied to produce a datalayer containing contiguous natural lands greater than 250 acres.  Because the MRLC National Landcover Datalayer originated as a grid with 30-meter cells, the polygon boundaries appear jagged at large scales.  The coverage is best displayed at statewide or regional scales and should not be used for site analysis.

ATTRIBUTES

NAT		Contains values of 1 for all "natural lands"
CONTIGACRE		Area in acres for contiguous natural lands polygons after being clipped for the WATRSHED library
ORIGACRES		Area in acres for the original contiguous natural land polygon greater than 250 acres, prior to being clipped

Selecting NAT = 1 will result in proper display and analysis of the data.  Note that this datalayer was originally developed as a single statewide coverage.  After being clipped into watershed-based tiles, some of the polygons originally delineated as contiguous natural lands (based on the process described above) were split into two or more polygons.  The CONTIGACRE item represents the acreage of the polygon after being clipped.  The ORIGACRES item is the acreage of the original, larger polygon that the newly-clipped polygon "belonged to" prior to clipping.

MAINTENANCE

MassGIS is maintaining this datalayer. Related layers include MRIP Riparian Corridors and MRIP Natural Land Riparian Corridors.

Last Updated 11/24/2004
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