Impact evaluation generates novel insights into MPA effectiveness

Establishing effective MPAs are a major goal of many marine conservation programs, with MPAs often expected to provide both fisheries and biodiversity benefits. Yet despite the rapid global expansion of MPAs, MPA... [ view full abstract ]

Establishing effective MPAs are a major goal of many marine conservation programs, with MPAs often expected to provide both fisheries and biodiversity benefits. Yet despite the rapid global expansion of MPAs, MPA effectiveness evaluation is often limited by a lack of appropriate monitoring designs and a disconnect between MPA objectives and the monitored outcomes. Here we use state-of-the-art impact evaluation techniques to assess a recently established MPA network in the Bird’s Head Seascape (BHS), West Papua, Indonesia. Coral reef ecological and fisheries data were collected approximately every 3 years since 2010 at >200 monitoring locations within and at control sites outside seven BHS MPAs. By using impact evaluation, it is possible to explicitly estimate MPA outcomes in comparison to the counterfactual (the outcome based on no MPA implementation). Matching techniques were used to pair sites within MPAs to outside control sites based on ten biophysical and anthropogenic variables (e.g. reef type and exposure, distance to deep water, distance to nearest human settlement and market etc.) previously reported to affect fish biomass and coral cover. We assessed the effectiveness of the MPA network for herbivorous and commercially valuable fish biomass and coral cover. Interestingly, when comparing using counterfactuals to assess effectiveness of the MPA network to traditional non-matched controls we found that some MPA impacts would have been underestimated, while others have been overestimated with traditional MPA monitoring designs. Using impact evaluation techniques such as these allows for causal inference of MPA effects, which subsequently can inform better-designed MPAs.