Ecological and socioeconomic impacts of marine protected areas in the South Pacific: assessing the evidence base
Marine protected areas (MPAs) in the South Pacific have a unique history that calls for a regional-scale synthesis of MPA impacts and the factors related to positive ecological and socioeconomic change. However, recommendations of best approaches to MPA implementation can be made only when evaluation techniques are sound. Impact evaluation involves quantifying the effects of an intervention over and above the counterfactual of no intervention or a different intervention. Determining the true impact of an MPA can be challenging because additional factors beyond the presence of an MPA can confound the observed results (e.g. differences in ecological or socioeconomic conditions between MPA and control sites). While impact evaluation techniques employing counterfactual thinking have been well developed in other fields, they have been embraced only slowly in the MPA evaluation literature. We conducted a structured literature search and synthesis of MPA evaluation studies from the South Pacific to determine: (i) the overall ecological and socioeconomic impacts of MPAs in the region, (ii) what factors were associated with positive, neutral, or negative impacts, and (iii) to what extent the MPA evaluation literature from the region has incorporated counterfactual thinking and robust impact evaluation techniques. Based on 52 identified studies, 42% of measured ecological impacts were positive. While 72% of socioeconomic impacts were positive, these were from only eight studies. The proportion of positive impacts was comparable between community-based and centrally governed MPAs, suggesting that both governance approaches are viable options in the region. No-take MPAs had a greater number of positive ecological impacts than periodic closures and there was little evidence of any long-term ecological recovery within periodic closures following harvesting. Importantly, more than half of the studies examined (59%) did not provide any clear consideration of factors beyond the presence of the MPA that might have confounded their results. We conclude that counterfactual thinking has yet to be fully embraced in impact evaluation studies in the region and recommend pathways by which progress can be made.