The role of trade-offs in biodiversity conservation planning: linking local management, regional planning and global conservation efforts.

Biodiversity conservation planning requires trade-offs, given the realities of limited resources and the competing demands of society. If net benefits for society are important, biodiversity assessment cannot occur without other sectoral factors "on the table". In trade-offs approaches, the biodiversity value of a given area is expressed in terms of the species or other components of biodiversity that it has that are additional to the components protected elsewhere. That "marginal gain" is called the complementarity value of the area. A recent whole-country planning study for Papua New Guinea illustrates the importance of complementarity-based trade-offs in determining priority areas for biodiversity conservation, and for designing economic instruments such as biodiversity levies and offsets. Two international biodiversity programs provide important new opportunities for biodiversity trade-offs taking complementarity into account. Both the Millennium Ecosystem Assessment and the Critical Ecosystems or "hotspots" programs can benefit from an explicit framework that incorporates trade-offs, in which a balance is achieved not only by land-use allocation among areas, but also by the crediting of partial protection of biodiversity provided by sympathetic management within areas. For both international programs, our trade-offs framework can provide a natural linkage between local, regional and global planning levels.