The world's system of protected areas has grown exponentially over the past 25 years, particularly in developing countries where biodiversity is greatest. Concurrently, the mission of protected areas has expanded from biodiversity conservation to improving human welfare. The result is a shift in favor of protected areas allowing local resource use. Given the multiple purposes of many protected areas, measuring effectiveness is difficult. Our review of 49 tropical protected areas shows that parks are generally effective at curtailing deforestation within their boundaries. But deforestation in surrounding areas is isolating protected areas. Many initiatives now aim to link protected areas to local socioeconomic development. Some of these initiatives have been successful, but in general expectations need to be tempered regarding the capacity of protected areas to alleviate poverty. Greater attention must also be paid to the broader policy context of biodiversity loss, poverty, and unsustainable land use in developing countries.

As global efforts to protect ecosystems expand, the socioeconomic impact of protected areas on neighboring human communities continues to be a source of intense debate. The debate persists because previous studies do not directly measure socioeconomic outcomes and do not use appropriate comparison groups to account for potential confounders. We illustrate an approach using comprehensive national datasets and quasi-experimental matching methods. We estimate impacts of protected area systems on poverty in Costa Rica and Thailand and find that although communities near protected areas are indeed substantially poorer than national averages, an analysis based on comparison with appropriate controls does not support the hypothesis that these differences can be attributed to protected areas. In contrast, the results indicate that the net impact of ecosystem protection was to alleviate poverty.conservation policy | poverty | empirical evaluation | protected areas | ecosystems

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