Landscape Characteristics - USEPA/ATtILA2 GitHub Wiki

Introduction

Natural land cover and anthropogenic land use have a profound effect on landscapes and environmental stressors. For example, cutting down forests reduces uptakes of nitrogen and other nutrients, disrupts habitats for various fauna, and exposes soils to increased runoff. Erosion may be further accelerated if the exposed area is on a slope. The proportions of various land cover/use types within a watershed can provide information about the expected condition of surface waters and aquatic habitats within that watershed.

The Landscape Characteristics toolset consists of the following metric tools:

  • Core and Edge Metrics Calculates the edge-to-area ratio within each reporting unit for selected land cover classes and creates an output table. Edge width is provided by the user.

  • Land Cover Diversity Calculates land cover diversity within each reporting unit and creates an output table. Metrics include Shannon-Weiner index, standardized Shannon-Weiner index, Simpson's index, and simple diversity.

  • Land Cover on Slope Proportions Calculates percentages of land cover types on slopes greater than a specified threshold value within reporting unit polygons and creates an output table.

  • Land Cover Proportions Calculates percentages of selected land cover types within reporting unit polygons and creates an output table. Optionally, per capita area of selected land cover types within each reporting unit may also be reported (square meters of land cover class per person).

  • Neighborhood Proportions Calculates the area percentage of selected land cover classes within a given neighborhood. The neighborhood is square in shape. Its size is provided by the user. An optional secondary raster can be created which reclassifies those values into percentage zones.

  • Patch Metrics Calculates the number of patches (NUM), largest patch size (LRG), average patch size (AVG), the number of patches per square kilometer (DENS), and proportion of largest patch area to total patch area (PLGP) within each reporting unit for selected land cover classes and creates an output table. Minimum patch size and maximum patch separation are provided by the user. Optionally, Mean Distance to Closest Patch (MDCP) within each reporting unit for selected land cover classes may also be calculated.

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