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• To make "area" and "length" comparable. The least fragmented shapepossible is a circle, and the area to circumference ratio can serve as a guidefor this.Because of the many conflicting factors inherent in the BLM, the best way toarrive at a good number is via experimentation. There are some key things tolook at to test the BLM’s "accuracy" at meeting goals, particularly in how themvbest file is set up. Adjusting BLM is all about how goals are met (under,precisely, overrepresented) (Ferdana, 2006). Please consult Game and Grantham(2008) for an excellent description on how BLM should be employed.g. Flexible / Low Irreplaceability Units: Areas that are not being indicated ashighly irreplaceable are not unimportant for conservation; they are more flexible--as there are other planning units that contain similar biodiversity. A highlyirreplaceable area may not be known locally for its biodiversity value, but may,for example, contain 100% of the occurrences of a particular target and istherefore irreplaceable for meeting the representation goal for that target. Marxanis also useful for highlighting areas that have previously been overlooked- forexample where goals for many targets can be met in a spatially cohesive mannerthat increases the likelihood of strategy effectivenessh. Unexpected Results: Targets, goals and cost surface are all crucial to creating thebest portfolios. If areas that are known to be important are not being reflected inthe portfolio it may be because the targets or the cost surface are not defined in away that distinguishes those areas as different from others. For example if nohighland targets are represented in the portfolios it may be because the targetshave not been stratified by elevation so those highland parts cannot bedistinguished as needing representation separate from the lowland areas. The goalrepresentation for that target will be met – but it could be all within lowland areas.3.2 Marxan Input File PreparationSuggested steps to follow when conducting a Marxan analysis are diagramed in the figureon the next page. In order to run the Marxan Tools, the user will need to prepare fourbasic data layers. These layers include:1. Conservation Targets. These are the habitats or species in which conservationgoals are set and can be represented as points, lines, or polygons. These featuresshould be previously screened as potential candidate sites for meetingconservation goals that are expressed in number of occurrences (points), area(polygons) or length (lines) in map units (i.e. hectares). If you are using a blockdefinition file, these goals can be expressed as percentages of the target’s totalun its . Species penalty factors can be assigned to each target depending on howimportant it is for each one to reach the conservation goal. It is recommended touse the Target Prep tool when preparing your targets for the Marxan InputTNC Protected Area Tools (PAT) Version 3.0The Nature Conservancy, August 200949