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Home A Biodiversity Conservation Plan for Papua New Guinea Based on Biodiversity Trade-offs AnalysisHow do we use the current priority set in the planning process? The current priority set is the current "best" set in light of the nominated target and all of the constraints. Unless it is the case that this priority set was to be implemented immediately, it is necessary to consider the special attention that might be given to a subsets of this set. Such considerations are useful even if the overall priority set does not change. However, it is necessary to re-evaluate the set as new information, including new costs or constraints, come to hand. We present examples of such modifications below, illustrating the way in which ongoing evaluations and re-assessments of priority areas can be made. Figure 4a shows the relative complementarity values of the members of the current priority set. The high complementarity areas and the 'must-have' areas, those that cannot be substituted for any others if the biodiversity target is to be reached, (Figure4b) might be the prime candidates for immediate allocation of scarce conservation resources. Figure 4c shows all the members of the current priority set having more than half their area in the highest PNGRIS land use intensity class. These might also be candidates for special attention - either urgency for action on formal protection, searching for substitutes where possible, or even rehabilitation. A similar map, not reproduced here, was produced for areas having highest population density. The timber volume index ranking of members of the current priority set is shown in Figure 4d. Once again, priority areas with high timber volume might be candidates for early action, since they are potentially vulnerable for logging. In addition, below we consider priority areas that overlap with the PNGFA forest plan areas of interest. The recent report, "A future for our forests" (National Research Institute 2000) recommends that "areas of forest identified as having high biodiversity values by the Conservation Needs Assessment and BioRAP process should be considered as possible constraints on forestry operations. The conditions under which such constraints would operate would need to be defined." The discussion above and maps from Figure 4 suggest to us that the form of "constraints" on high value biodiversity areas could be realized through a process where the current set be recorded with PNGFA and OEC and must-have areas for the 15%-based target be "no-go" areas, while others be provisional no-go areas, unless substitute areas are identified and agreed to by PNGFA and Office of Environment and Conservation (OEC). Faith et al. (2001b) explore some other incentives/constraints strategies, including possible assignment of high environmental levies based on complementarity values.
Timber volume per unit area as an alternative cost Among that set of 50 priority areas, 6 areas had distinctively high values for timber volume per unit area. These are shown in Figure 5b and summarised in Table 4. These 6 RMUs were deleted from the proposed set and a search was made for substitutes. Three substitute areas were found for this set of 6. Figure 5b shows the substitutions that were made. The opportunity cost (index of timber volume) was reduced from 93,218 to 92,562 units (see summary properties in Table 2 for analysis of Figure 2a) This lower cost result highlights the fact that our TARGET algorithm only approximates the least-cost solution, and subsequent swaps may improve the result.
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