Use of many low-level conservation targets reduces high-level conservation performance

The prevalent approach for reserve network design is within the framework of systematic conservation planning which includes target setting as an integral step. In target-based planning the conservation goal is translated into conservation targets for biodiversity features, such as species, habitats or ecosystem services. In effect, many targets are set for factors that can be considered as low-level components of biodiversity as a whole. This paper investigates the relations between common formulations for reserve selection, including minimum set cover, maximum coverage and maximal utility planning. We conclusively show how the use of many low-level targets can significantly reduce return on conservation investment. This finding should influence the way targets are viewed in systematic conservation planning, and it is directly relevant for globally accepted state-of-the-art conservation practices. We also describe a novel planning framework combining target- and benefit-based approaches which could be widely useful in the design of conservation area networks.