Breaking Silos: A Systemic Portfolio Approach and Digital Tool for Collaborative Urban Decarbonisation

Urban decarbonisation requires governance models that overcome the fragmentation and rigidity of traditional urban planning. This article presents a systemic and digital framework for managing urban decarbonisation portfolios aligned with the EU Mission for Climate-Neutral and Smart Cities. Grounded in systems thinking and portfolio theory, this study develops an analytical taxonomy and an interactive digital tool to support strategic coordination, multistakeholder collaboration, and adaptive decision-making. The framework is empirically validated through the case of Madrid’s Climate City Contract, demonstrating its functionality and transferability. Using a mixed-method approach—combining co-creation workshops, interviews, document analysis, and iterative prototyping—this research maps interdependencies among projects, actors, and levers of change. The digital tool enables real-time visualisation of collaboration patterns, gaps, and synergies, enhancing strategic foresight and coordination capacity. Findings reveal that 75% of initiatives in Madrid’s CCC address climate adaptation, 80.36% are linked to knowledge generation, and key anchor projects serve as integrative hubs within the portfolio. This study concludes that the portfolio approach strengthens systemic innovation and reflexive governance by integrating digital infrastructures with collaborative planning processes. While challenges persist—including data integration, institutional capacity, and political dynamics—this research offers a replicable methodology for embedding mission-oriented strategies into urban governance. The digital portfolio emerges as a complementary governance tool that enhances transparency, organisational learning, and alignment across governance levels.