A regional approach to planning trade-offs in mid-sized towns: the case of Frankfurt Rhine-Main

This study explores the planning trade-offs generated by the conflicting infill development and green space preservation objectives in the Frankfurt Rhine-Main (FRM) region through a social-ecological systems (SES) perspective. The main research question is: How can the conflict between infill development and green space preservation objectives in the growing mid-sized towns be resolved by planning instruments? To answer this question, the analysis combines spatial assessment of settlement development and green space parameters in selected towns with an evaluation of institutional conditions. Findings show that limited capacities at administrations, bureaucratic hurdles and policy-practice divides are the main systemic impediments weakening institutional conditions to effectively handle trade-offs. A city-wide decision-making instrument is proposed to be coordinated regionally, which systematically evaluates spatial reserves either for infill development (e.g., residential development at the site of an underused parking lot with close proximity to everyday utilities) or for green space preservation (e.g., green space protection to ensure connectivity for fresh air corridors). Since housing and labour market dynamics, commuting, and regionally-significant green spaces function across municipal borders, the studied trade-offs are inherently regional. Regional-level institutions should contribute through initiating and coordinating this at the stage of preparatory land-use planning. Coordinating decisions at the regional-scale with the proposed SES-based tool sustains long-term regional attractiveness and competitiveness by avoiding and managing externalities such as congestion, urban overheating and ecological fragmentation. This instrument would require the SES approach to be operationalised at the regional-level administration, but can in turn ensure a systemic, unbiased and transparent practice for land-use decisions at the local level.