First application of the conservation and human use index (CHUI) for the evaluation of coastal social-ecological conditions across ten European case studies

Social-Ecological Systems (SESs) are shaped by complex interactions between natural processes, governance structures, environmental pressures, and human perceptions. To evaluate these multidimensional dynamics in diverse transboundary coastal areas, this study presents the first application of the Conservation and Human Use Index (CHUI) across ten case studies representing contrasting ecological, institutional, and socio-cultural contexts. The CHUI, grounded in the Social-Ecological Systems Framework (SESF), operationalises system performance through 134 standardised indicators spanning four equally weighted dimensions: Resource System, Environment, Governance, and Actors. Indicators were identified by scientific literature, management documents, and cross-stakeholder consultations, enabling qualitative insights to be translated into semi-quantitative metrics through a harmonised scoring protocol. Results reveal marked variation among the identified case studies, reflecting distinct combinations of ecological conditions, exposure to anthropogenic and climatic pressures, governance effectiveness, and the quality of human-nature relations. Overall, the first CHUI assessment results demonstrate the tool’s effectiveness as both a diagnostic framework and a comparative platform for identifying leverage points, guiding adaptive governance, and supporting integrated coastal management. It highlights the importance of balancing ecological protection, institutional strength, and socially legitimate processes to enhance the assessment of baseline conditions and system vulnerabilities across coastal SESs.