Development and application of the Eco-Geomorphological Dune Value Index (EGDVI) for assessment of conservation status: a pilot case at the Strandzha Black Sea Coast, Bulgaria

Coastal dune systems are dynamic and vulnerable landforms that provide key ecological, geomorphological and protective functions along the Bulgarian Black Sea coast. Despite their importance, their conservation status remains insufficiently quantified, particularly under the microtidal and fetch-limited conditions characteristic of the Black Sea. This study introduces the Eco-Geomorphological Dune Value Index (EGDVI), a multi-criteria assessment framework integrating 31 indicators across eight thematic categories, encompassing geomorphological, ecological, anthropogenic, legal and scientific dimensions. Unlike existing dune assessment approaches, the EGDVI combines these components within a single weighted and standardised scoring system, enabling a comprehensive and policy-relevant evaluation of dune systems. Indicator scores are derived from field surveys, high-resolution remote sensing data, GIS analysis and legislative sources and are weighted through structured expert elicitation. The EGDVI was applied to 16 dune systems along the Strandzha sector of the Bulgarian Black Sea coast. Total scores range from 154.0 to 364.5 (maximum 400), defining five classes of eco-geomorphological value. Four systems (25.0%) are classified as Very High Value (Class A), one (6.25%) as High Value (Class B), eight (50.0%) as Moderate Value (Class C), one (6.25%) as Low Value (Class D) and two (12.5%) as Degraded (Class E). At the regional scale, the mean EGDVI score (266.1) falls within the moderate-value class, indicating that transitional dune systems dominate along the Strandzha coast. The results demonstrate that the EGDVI provides a robust, transparent and reproducible framework for assessing both condition and conservation value. By explicitly incorporating governance and scientific dimensions alongside eco-geomorphological parameters, the index strengthens the science–policy interface and supports conservation prioritisation. The conceptual structure of the EGDVI is transferable to other microtidal and enclosed-sea coastal environments, provided that indicators are locally calibrated.