Methodology for scaling mitigation and compensatory measures in tropical marine ecosystems - MERCI-Cor HandBook 2

Methodology for Scaling Mitigation and Compensatory Measures in Tropical Marine Ecosystems (MERCI-Cor) provides an operational framework to quantify ecological losses and gains linked to coastal development affecting coral reef ecosystems. The guide adapts the MERCI/UMAM family of Rapid Assessment Methods to the specificities of tropical marine habitats, enabling practitioners, managers and regulators to assess ecological integrity, compare development scenarios, and design compensatory actions aligned with the “no net loss” principle. The handbook details a three-step approach: (1) qualitative characterization of impacted and compensation areas, (2) quantitative scoring of ecological states before and after impact using standardized indicators, and (3) calculation of adjusted losses and gains integrating risk and time-lag factors. It also describes procedures for selecting compensation sites, choosing ecological engineering techniques (coral transplantation, artificial reefs, post-larval capture, eco-design of infrastructures), and planning long-term monitoring. By combining scientific robustness, transparency, and ease of implementation, MERCI-Cor provides a practical, reproducible, and regulator-compatible tool to estimate compensation ratios, evaluate ecological equivalence, and support the mitigation hierarchy in tropical marine development projects