OVERVIEW

Supporting Natural Landscape is one of two datalayers resulting from the BioMap biodiversity mapping project (also see the NHESP BioMap Core Habitat datalayer description). The Supporting Natural Landscape buffers and connects Core Habitat polygons, which depict the most viable habitat for rare species and natural communities in Massachusetts, and identifies large, naturally vegetated blocks that are relatively free from the impact of roads and other development. The quality of undeveloped land considered in the landscape analysis was evaluated based on four major components:

• natural vegetation patch characteristics;
• size of relatively roadless areas;
• subwatershed integrity;
• and contribution to buffering BioMap Core Habitat polygons for plants and exemplary communities.

These components were represented in seven Factor Maps in 30-meter x 30-meter raster datasets:

• size of natural vegetation patch;
• distance from development;
• forest history;
• size of individual roadless blocks;
• size of aggregated roadless blocks;
• subwatershed integrity;
• and distance to BioMap Core Habitat.

A weighted overlay was performed on these Factor Maps using the Model Builder extension of Spatial Analyst in ArcView 3.2a to produce the Supporting Natural Landscape datalayer.

This single statewide layer is stored in the State library; its coverage and layer name is BIOSNL.

Supporting Natural Landscape is a product of the weighted and additive overlays of seven Factor Maps. The Factor Maps are derived from both external and internal sources. External data includes the National Land Cover Data (U.S. Geological Survey and U.S. Environmental Protection Agency), Massachusetts Highway Department Roads (USGS, Roads Digital Line Graphs, and the Massachusetts Highway Department), Land Use (MassGIS), 1830’s-era Land Use (Harvard Forest), Ecoblocks (The Nature Conservancy), and Drainage Sub-basins (MassGIS). Internally-created data, based on external data, includes Developed Lands and Natural Vegetation, or Undeveloped Land, from the National Land Cover Data. For each Factor Map, each grid cell received a score, ranging from 0 (no quality) to 9 (high quality). The categories for each Factor Map were derived with reference to scientific literature where possible and otherwise on expert opinion. Individual Factor Maps were then assigned weights to reflect their relative importance in determining ecological value relative to other maps. All the overlay processes were done per eco-region.

In the first weighted overlay process, the following Derivative Intermediate Maps with 0 to 20 classes were created:

• Natural Vegetation from size of natural vegetation patch, distance from development and forest history;
• and Roadless Blocks from size of individual roadless blocks and size of aggregated roadless blocks.

Finally, a weighted overlay of the Natural Vegetation and Roadless Block Derivatiave Maps along with the Subwatershed Integrity produced the final scaled weighted overlay map. Then, using an additive overlay this final Factor Map was combined with the Distance to BioMap Core Habitat produced the Supporting Natural Landscape.

The selection of Supporting Natural Landscape was determined by selecting a total of 40% to 50% per ecoregion by the combination of BioMap Core Habitat with Supporting Natural Landscape. The most highly ranked grid cells in each ecoregion were selected for inclusion in BioMap, and thus the highest quality remaining habitat is represented in each ecoregion. As the amount of Core Habitat varies from ecoregion to ecoregion, the amount and the quality of Supporting Natural Landscape also varies. All the cells selected by ecoregion were then merged together to form a statewide map. Performing the landscape analysis by ecoregion created gaps in the Supporting Natural Landscape across ecoregional boundaries. The nearest neighbor interpolation technique filled in these artifacts by assigning new values. Finally, the raster layer was converted to vector format. Polygons that were not contiguous with BioMap Core Habitat and polygons that were less than 2,500 acres were deleted from the final map because the main intention was to buffer and connect Core Habitat polygons and to identify the largest remaining patches of undeveloped land. Isolated polygons larger than 2,500 acres that were not highly fragmented were retained. As a final step, the Supporting Natural Landscape polygons were compared with 1:5,000 digital orthophotos (1992-1999) and recent areas of development were deleted.

The BIOSNL.PAT (polygon attribute table) contains the following items:
 

BIOSNLID		16		16		C		NHESP Unique identifier
BIOSNLPOLY		1		1		I		1 = SNL polygons 0 = "interior" polygons (not SNL)

• · The legend that MUST accompany this datalayer on ALL maps is: 

"NHESP BioMap Supporting Natural Landscape".
• Please note that Supporting Natural Landscape polygons were designed for use at a regional or town scale. For accurate portrayal, the data should be displayed at scales of less than 1:25,000 (e.g. 1:30,000).
• This datalayer is intended for conservation planning purposes only- it has no regulatory purpose. The NHESP layers designed for regulatory use are produced in the Natural Heritage Atlas.

In June 2002 a few very small natural commuities were removed from the BioMap Core Habitat layer, and this layer was updated to reflect those changes. Questions about this datalayer should be directed to NHESP at 508-792-7270 x300.

• The BioMap Core Habitat datalayer was designed to delineate most viable habitat for rare species and natural communities in Massachusetts.  See the metadata for that datalayer for more detail.
• The Natural Heritage and Endangered Species Program has published two reports:
• ‘BioMap: Guiding Land Conservation for Biodiversity in Massachusetts’, a full color report on the BioMap project
• ‘The BioMap Technical Report’, which presents much greater technical detail on the methodology used to develop the BioMap, along with the scientific basis for these methods.
See http://www.state.ma.us/dfwele/dfw/nhesp/nhbiomap.htm for information on receiving these two reports for more detail on the criteria and methodology involved in producing the Surrounding Natural Landscape datalayer.

Last Updated 6/13/2003
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