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values, expert opinion should be used in assigning a maximum influence distance that <strong>the</strong>risk element may have on a particular habitat or realm. The program calculates intensitydecay from <strong>the</strong> edge of each risk element using <strong>the</strong> user-specified influence distance anddistance decay function. For example, in <strong>the</strong> file called “risk_ag_sugarcane.shp” <strong>the</strong>re isa terrestrial influence distance of 1000 meters, or 1 kilometer. If <strong>the</strong> user chooses to use alinear decay function (default), <strong>the</strong> intensity value of 11 will be assigned within closeproximity of <strong>the</strong> boundaries of each sugarcane polygon, but as you move away from <strong>the</strong>polygon, <strong>the</strong> intensity becomes linearly smaller and smaller until you reach a distance of1000 meters, where <strong>the</strong> intensity is reduced to zero (0). In <strong>the</strong> figure below, <strong>the</strong>re is anexample of an ERS model output for a paved road with an intensity value of 30 and aninfluence distance of 300 meters. Notice <strong>the</strong> linear decay function that is applied like abuffer completely around <strong>the</strong> risk element in all directions. Additional guidance onsetting up intensity values and influence distances for a variety of socioeconomicactivities can be found in (McPherson et al., 2008).An example of ERS model output for a paved road risk element with anintensity value of 30 and an influence distance of 300m. Notice <strong>the</strong> lineardecay function that is applied like a buffer completely around <strong>the</strong> riskelement in all directions.TNC Protected Area Tools (PAT) Version 3.0The Nature Conservancy, August 200916

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