Practical application of biodiversity surrogates and percentage targets for conservation in Papua New Guinea

A conservation planning study in Papua New Guinea (PNG) addresses the role of biodiversity surrogates and biodiversity targets, in the context of the trade-offs required for planning given real-world costs and constraints. In a trade-offs framework, surrogates must be judged in terms of their success in predicting general biodiversity complementarity values - the amount of additional biodiversity an area can contribute to a protected set. Wrong predictions of low complementarity (and consequent allocation of non-protective land uses) may be more worrisome than wrong predictions of high complementarity (and consequent allocation of protection, perhaps unnecessarily forgoing other land uses benefiting society). Trade-offs and targets work well when predictions of complementarity are based on surrogate information that is expressed as a continuum of variation. The PNG study used hierarchical variation for environmental domains and vegetation types, and a nominated target then dictated the level within those hierarchies that was used. Internationally-promoted targets provide a potential basis for comparative evaluation of biodiversity protection levels among countries or regions. However, conventional application of percentage targets, in focusing on proportions of local area or on proportions of habitat types, does not serve the goal of biodiversity protection or sustainability well because targets can be miss-used to restrict the amount of biodiversity protected. At the same time, recent complaints about percentage targets are equally misguided in claiming. based on species-area curves, that 10% targets imply 50% extinctions. We apply a new approach to percentage targets in PNG, in which the maximum diversity that could be protected by an unconstrained 10% of the total area of the country becomes the working biodiversity target. Reaching that same biodiversity target may then require more than 10% of the area, because of constraints (e.g., existing reserves) and costs. In the baseline analysis for PNG, we found that hierarchical variation at the level of 56A vegetation types, combined with the 608 environmental domains, could be protected in an unconstrained 10% of the country. This process of determining a biodiversity target also revealed some "must-have" areas for any future conservation plan. Such must-have areas were also identified for a 15%-based target. The satisfaction of the 10%-based target in practice required 16.8% of PNG (Faith et al. 2001a). This low-cost proposed protected set corresponded to greater net benefits relative to our application of two conventional targets approaches