Coral reef monitoring in French overseas territories: status, knowledge gaps, and improvements to meet national and European environmental policy objectives

Coral reefs are among the most diverse and productive ecosystems on the planet, providing goods and services to millions of people. Yet, they are threatened by a combination of natural and anthropogenic disturbances, which are increasing in both frequency and intensity. With 9% of the world's coral reef area, France is the 4th largest coral reef country, which confers a significant responsibility in terms of conservation. This synthesis evaluates the major coral reef monitoring programs in French overseas territories, aiming to identify gaps and proposing strategies to fulfill national (the French Coral Reef Initiative – IFRECOR, and the National Strategy for Protected Areas – SNAP) and European (the Water Framework Directive – WFD) requirements. We show that, despite a disparity in terms of objectives, implementation periods, spatial extent, and biological variables, these programs still represent a critical tool to inform stakeholders, managers and scientists about ecological changes. We emphasize that while these monitoring programs can be improved to meet the expectations of national public policy, such as through the use of common sampling strategies and multivariate indices that incorporate key ecological and functional processes, our analysis clearly demonstrates that several major requirements of the WFD are incompatible with coral reef monitoring programs. Establishing a reference point, determining alert thresholds, distinguishing natural and anthropogenic sources of disturbance, and the contrast between the allocated remediation time and the recovery cycles of benthic communities are fundamental obstacles to the application of the WFD for ecosystems as dynamic, diverse and complex as coral ecosystems.