Beyond the concept: how boundary spanning is implemented at the science-policy-practice interface to tackle complex societal challenges

Effective responses to today’s complex societal challenges, spanning health, environment, and climate change and social sustainability domains, require evidence-informed policymaking supported by collaboration across disciplinary and institutional boundaries. Boundary spanning offers a promising approach for bridging the science–policy divide, yet its implementation in practice remains underexplored. This review examines how boundary spanning is operationalised at the science-policy-practice interface, and the conditions that enable or constrain its effectiveness. A structured search of peer-reviewed and grey literature was conducted across PubMed, Web of Science, Scopus, and Google, with studies screened and included based on criteria emphasising practical, real-world implementation. Using a narrative synthesis and cross-sector comparative analysis, the review identifies diverse initiation pathways, operational models, and sustaining mechanisms of boundary spanning. While approaches differ across domains, from embedded roles in public health to institutional and networked arrangements in environmental governance and hybrid models in climate and sustainability, a consistent pattern emerges. Boundary spanning often begins with relationship-based, individual practices grounded in trust, and over time progresses towards institutionalisation, supporting its continuity and scale. These findings highlight the need for theory-informed, context-sensitive evaluation frameworks to understand how trust develops and translates into institutionalisation. Advancing these areas is critical to strengthening the visibility, legitimacy, and impact of boundary spanning in evidence-informed policymaking.