Urban Morphology Links Green Space and Compact City Policy in a Shrinking Japanese Metropolis

Abstract The "compact city" model, a central tenet of sustainable urbanism, creates critical policy tensions in post-industrial nations, where land use intensification often conflicts with urban shrinkage and the need to preserve urban green space (UGS). This study addresses a significant research gap by moving beyond city-level metrics to conduct a fine-grained morphological analysis of urban form and UGS provision at the urban block level. Using Nagoya, Japan, as an archetypal case study of a city facing simultaneous compaction and shrinkage, we develop a comprehensive urban block typology through a GIS-based hierarchical classification. The analysis reveals a stark spatial polarization: block types embodying the compact city ideal (high-density commercial and residential) are the most green-deficient, characterized by small, fragmented, and morphologically inefficient non-built-up areas. Conversely, peripheral and specialized blocks (e.g., woodlands, farmland) function as the city's primary green reservoirs. These findings provide high-resolution evidence for the compact city-green space paradox, identifying the morphology of non-built-up space as a key mechanism of green exclusion. We contribute a transferable methodological framework that can be repurposed as a Planning Support System (PSS). Policy Implications: This typology enables a targeted "right-sizing" and greening strategy, allowing planners and policymakers to use morphological analysis to identify specific blocks for green infrastructure acquisition and land use interventions. This provides a practical tool for land use governance, helping to reconcile densification policies with the need for equitable and resilient urban environments.