Nature-based Solutions (NbS) offer significant potential to address climate change while promoting sustainable development. However, their long-term success is often hindered by organisational, financial, and knowledge-related challenges, with collaboration emerging as a critical yet complex factor. While collaboration facilitates stakeholder engagement and enhances NbS implementation, it also introduces barriers, such as conflicting interests, institutional rigidity, and resource constraints, that can undermine project outcomes. This paper proposes a methodological framework that can potentially facilitate collaborative processes for the implementation of NbS. Departing from a systematic analysis of documental evidence available for the implementation of 11 NbS projects within the Horizon 2020 framework, the research identifies recurring collaboration challenges and suggests potential tools to address them. The proposed tools are inspired by the principles of Service Design, a multidisciplinary field merging behavioural sciences, technology, and design proven to have created both tangible and intangible elements for design solutions. The proposed tools utilise hybrid perspectives, combining traditional methodological approaches and innovative instruments, including technology and artificial intelligence instruments. The findings highlight diverse forms of collaboration, such as co-design and co-governance, driven by the involvement of key stakeholders, including community members, policymakers, NGOs, and academic institutions. The proposed SD tools provide practical solutions to overcome barriers, ensuring equitable and effective NbS implementation. This study underscores the importance of integrating structured, stakeholder-centered approaches to address collaboration challenges and enhance the impact of NbS. Future research should focus on applying the proposed framework in practice, gathering empirical evidence to refine and adapt it for diverse contexts.

Community-led urban interventions are shaped by uncertainties that affect their initiation, development, operation, and short- and long-term outcomes. Existing research offers insights into participatory practices but lacks a comprehensive framework for understanding how community initiatives evolve under uncertain conditions. In this paper, we develop a realist, process-oriented framework that integrates the logic model, uncertainty analysis, and context–mechanism–outcome configurations to examine the lifecycle of urban interventions and the effects of community-based mechanisms on these processes. The framework distinguishes six types of uncertainty: ambiguity, variability, event, systemic, ecological, and epistemic. It is then applied to seven community-led urban interventions across diverse contexts. The findings suggest that specific uncertainties can be associated with particular mechanisms: ambiguity with sense-making and co-design; variability with coordination, stewardship, and adaptive learning; and systemic uncertainty with sense-making. Additionally, similar mechanisms can produce different outcomes when operating in different contexts. The main output of the paper is a realist evaluation framework for understanding how community-led urban interventions respond to different types of uncertainty and support the social, environmental, governance, and learning dimensions of sustainability while helping practitioners and policymakers mobilize appropriate mechanisms under specific conditions of uncertainty.