Integrating Collaborative Governance and Environmental Performance Assessment for Nature-Based Solutions: The euPOLIS Experience in Palermo

Nature-Based Solutions (NBSs) are increasingly recognized as strategic tools for climate adaptation and urban regeneration, yet their implementation requires balancing environmental performance, territorial identity, and governance feasibility. This article investigates the application of the euPOLIS H2020 methodology in Palermo, Italy, focusing on the proposed transformation of Villa Turrisi—a residual peri-urban agricultural area representing one of the last remnants of the historical Conca d’Oro landscape—into a new public green infrastructure within the framework of the new Municipal Development Plan (PRG/PUG). This study examines how a structured co-design process involving municipal actors, citizens, and local associations can be coupled with ecosystem service assessments. Rather than selecting a single optimal design, the analysis evaluates two alternative vision scenarios—a multifunctional framework aligned with euPOLIS principles and an intensive urban forest model—to generate quantitative and qualitative baseline data. Environmental indicators (carbon sequestration, microclimatic regulation, and hydrological resilience) are used not as deterministic selection criteria but as theoretical decision-support evidence within a predominantly qualitative, value-driven local planning process. The core contribution of this work lies in demonstrating the operational transferability of the euPOLIS framework from front-runner to follower cities within a Mediterranean planning context. The Palermo case shows how quantitative environmental simulations can effectively inform—rather than dictate—participatory governance, heritage preservation, and regulatory feasibility. Ultimately, this article offers a transferable planning and policy framework that bridges European NBS research with municipal decision-making, providing actionable insights for integrating climate-resilient green infrastructure into local urban plans.