Twenty years of marine systematic conservation planning: a global scoping review for good practices.

Human activities are exerting increasing pressure on the ocean, threatening marine biodiversity and the many benefits it provides to people. Allocating adequate space to enable the sustainable and equitable use of the ocean resources, while ensuring cost-effective conservation and restoration of marine ecosystem is particularly challenging in light of ambitious global, regional, and national commitments, such as those established by the Global Biodiversity Framework. In this context, Systematic Conservation Planning (SCP) offers a robust framework to prioritize conservation actions that safeguard biodiversity while minimizing costs and facilitating dialogue among maritime sectors. The scoping review here assesses the challenges in SCP implementation and the obstacles preventing its adoption in guiding decision-making for the achievement of conservation objectives in harmony with human uses of marine resources. The 149 studies analysed, spanning from 2002 to early 2023, are distributed across all continents and encompass nine biogeographic realms. Our analysis shows that only a limited number of SCP-based spatial plans have been implemented and just one study explicitly demonstrated the attainment of conservation targets defined through the SCP process. Inadequate criteria for assessing plan effectiveness and weak linkages between academic research and management practice were identified as significant impediments to the effective implementation of SCP outcomes. The review synthetizes context-specific recommendations, emphasizing that good practices vary across countries according to their geopolitical and economic settings, from small island developing states to middle- and high-income countries. Our study highlights that aligning SCP objectives with international policy frameworks is essential for addressing gaps in conservation and restoration planning and for embedding SCP within global governance processes.