The Phytopolis Strategy: Redesigning Barcelona, Copenhagen, and Paris Through Green Climate-Risk Infrastructure

Urban climate risks increasingly manifest through compound heat–flood dynamics that exceed the coping range of conventional grey infrastructure and sectoral planning. Nature-based solutions (NBS) are therefore shifting from “add-on greening” towards urban-scale climate-risk infrastructure, where soil, vegetation, and blue–green networks are designed, financed, and governed as core public systems delivering adaptation, mitigation, and health co-benefits (European Commission, 2015; IPCC, 2022). This chapter develops a comparative analysis of three European frontrunner cities—Barcelona, Copenhagen, and Paris—focusing on (i) the unit of action used to scale interventions, (ii) the delivery and economic mechanisms enabling implementation, and (iii) the performance evidence and indicators used to justify, prioritise, and evaluate projects. Methods combine document analysis of municipal plans, regulatory instruments, and financing arrangements with a targeted review of peer-reviewed literature on urban health, climate adaptation, and NBS effectiveness. Barcelona’s Eixample “green axes and squares” programme operationalises climate-risk infrastructure through a street-grid transformation (e.g., Consell de Cent and Girona) aligned with mobility and public-space redesign. Copenhagen’s Cloudburst Management Plan structures investments by hydrological catchments and a co-financing model between municipality and utility (e.g., Enghaveparken; Sankt Kjelds Plads). Paris leverages regulatory reform (PLU bioclimatique), municipal greening programmes, and green bond finance (Paris Climate Bond), with emblematic cooling projects (e.g., Place de Catalogne; streets and school-adjacent greening). By synthesising scaling logics, governance and finance, and measurable outcomes, the chapter contributes an operational framework for NBS as climate-risk infrastructure, relevant to trends in urban policy, climate adaptation, and delivery models for large-scale implementation.