Regional Variations in Nature Exposure: Development of a Multidimensional Green-Blue Space (GBS) Index for Mental Health Research and Policy

This paper introduces a novel Multidimensional Green-Blue Space Index (GBSI) to quantify access to natural environments for mental health research and policy applications. Using Geographic Information Systems (GIS) and Analytic Hierarchy Process (AHP), we develop a comprehensive index that incorporates both accessibility and quality characteristics of green and blue spaces. Six categories of environmental features were evaluated: active green spaces, passive green spaces, blue spaces, areas within 300m of active green spaces, areas within 300m of passive green spaces, and areas within 300m of blue spaces. Expert elicitation with nine specialists from five UK universities established the relative importance of these features using pairwise comparisons, yielding weights subsequently used in the GBS Index calculation. The resulting index was applied to Lower Layer Super Output Areas (LSOAs) across England, revealing significant spatial heterogeneity in access to quality green-blue spaces. The methodology enables identification of areas with insufficient access to health-promoting environments and facilitates evidence-based decision-making for spatial planning and mental health policy interventions. This spatially explicit approach demonstrates how quantitative spatial analysis can support targeted public health strategies aimed at enhancing population wellbeing through environmental planning.