Multi-criteria evaluation of blue nature-based solutions: Suitability of Posidonia oceanica in the Mediterranean Sea under climate scenarios

This study proposes a GIS-based Multi-criteria Approach for Suitability of NBS (MAS-NBS) to indicate the environmental suitability of coastal areas in the Mediterranean eco-region for NBS implementation through P. oceanica seagrass meadows under different climate change (CC) scenarios. Building upon our previous baseline analysis of P. oceanica environmental suitability in the region (Ozkiper et al., 2024), this future scenario analysis aids in developing adaptive strategies by considering potential changes in the suitability of Blue-NBS over the long term under different scenarios (i.e., different RCPs). MAS-NBS is performed using the Analytic Hierarchy Process (AHP), a widely used MCDA technique in ecological and spatial decision-making contexts. Compared with alternative MCDA methods (e.g., TOPSIS, fuzzy logic), AHP allows explicit pairwise comparisons and integrates expert judgment transparently. The analysis builds upon the consideration of optimum and threshold values, as well as the prioritization of various environmental variables crucial for the survival and growth of seagrass meadows. The synergistic effect of AHP and GIS in the developed approach enhances the assessment of suitability for P. oceanica meadows and supports decision-makers in designing marine and coastal NBS. While previous assessments focused on local scales or baseline conditions, this study provides the first basin-scale Blue-NBS suitability analysis for the Mediterranean under climate scenarios, explicitly incorporating expert knowledge for forward-looking spatial planning.