Bigger or better: the relative benefits of protected area network expansion and enforcement for the conservationof an exploited species

The global portfolio of protected areas is growing rapidly, despite widely recognizedshortfalls in management effectiveness. Pressure to meet area-coverage and manage-ment effectiveness objectives makes it essential to determine how limited conserva-tion funds should be allocated between expanding protected area networks and betterenforcing existing reserves. We formally explore this question for the particular caseof an exploited species in a partially protected system, using a general model linkingprotection, enforcement and legal/illegal resource extraction. We show that, on aver-age, funds should be disproportionately invested in enforcement rather than expan-sion. Further, expansion alone, without additional enforcement, can actually reduceconservation outcomes. To help guide future decisions, we calculate the optimal allo-cation of resources between these two actions given any current level of enforcementand protected area coverage. In most cases, simultaneously investing in expansion andenforcement is the optimal decision. However, in places with low enforcement andhigh protection, protected area contraction, or strategically concentrating enforcementeffort, produces the greatest benefits.