There has been recent debate over the role of predator-proof fences in the management of New Zealand’s biodiversity. The debate has arisen due to concern that investments in fenced sanctuaries are less productive than are alternative ways to manage biodiversity. Predator-proof fences are costly and budget constraints limit the area of habitat that can be fenced. The area of habitat enclosed within fences, and number of individuals of species supported, determines project’s ability to contribute to biodiversity goals. Many fenced sanctuary projects require substantial, continuing volunteer input to monitor fences and other tasks. These projects often pursue a number of goals including species protection, habitat restoration, education and community engagement. In this paper we examine methods to evaluate fenced biodiversity projects. While Cost Benefit analysis can potentially be used to evaluate these projects, cost - effectiveness measures and multi criteria analyses provide useful ways to inform decision-makers.