Assessing and optimizing the effectiveness of protected areas along China's coastal region: A social-ecological protected area network study.

Effectiveness of protected areas (EPA) evaluation has been used to measure the effectiveness of existing protected areas (PAs) and to identify prioritized and inefficient PAs. However, the current EPA evaluation remains incomplete, primarily due either to the scale of evaluation focusing on only isolated PAs without considering network connectivity or to the difficulty of balancing social and ecological synergy in practice. To address this issue, we proposed a social-ecological connectivity pathway to maximize the evaluation and optimization of EPA in a coastal region: first, we selected social and ecological indicators for habitat suitability evaluation and simulated the protected area network (PAN); second, we evaluated the rationality of network connectivity; and ultimately, we identified conservation gaps to the post-2020 global biodiversity target. Considering the complexity of coastal ecosystems, we selected the four coastal cities of the Shandong Peninsula, China as a case study. We find that (1) the social-ecological PAN consists of 370 primary corridors and 110 secondary corridors; there are 12 cross-ecosystem types in the identified PANs, three of which span marine to terrestrial ecosystems, while the remaining nine span terrestrial interior ecosystems; (2) 66 nodes were identified as spatial gaps; the benefit gap indicated that 51.75% of PAs were inefficiently protected but 48.25% were appropriately protected; regarding quantity gap, the marine PAs gap (25.41%) is much larger than the terrestrial PAs gap (15.80%), suggesting a possible priority in the marine PAs appropriately. Our study reveals that the EPA in the coastal region is currently weak and urgently needs to improve. Thus, we propose measures to optimize the EPA and suggest its potential application to other PAs in complex and vulnerable coastal regions.