The planning problem
The Nature Conservancy (TNC) recently initiated a new program to assemble ecoregional portfolios of conservation lands that collectively represent viable examples of all native species and plant communities. The initial steps involve selecting a set of target elements (i.e., species and communities), identifying levels of representation for each target, and then identifying a set of sites (the “conservation portfolio”) from among a larger set of “planning units” within the ecoregion. This portfolio provides a systematic basis for site planning and acquisition. The overall objective of the portfolio selection process is to minimize the “cost” of the portfolio while ensuring that all conservation goals for representation and spatial configuration have been met.