Urban Environmental Sustainability via Nature-Based Solutions in South Asia: A SETS Synthesis and Science Mapping (2000–2025)

This study examines how urban research on nature-based solutions (NbS) in South Asia has evolved and how it compares with global trends, using a systems-based framework that integrates social, ecological, and technological dimensions. We synthesize peer-reviewed urban NbS scholarship published between 2000 and early 2025, comparing a South Asia–focused corpus with a global benchmark set of studies explicitly grounded in systems thinking. Using systematic screening and bibliometric network analyses, we trace thematic structures and their evolution over time to identify strengths, gaps, and governance implications. The analysis shows that South Asian NbS research has developed strong ecological and technological capabilities, particularly in heat mitigation, land-cover dynamics, greenspace analysis, and stormwater management. However, issues related to governance, participation, equity, and health remain less prominently integrated than in the global benchmark literature, which exhibits a more governance-oriented configuration. Although integrative social–ecological–technological perspectives have increased markedly since 2019, overall thematic patterns in South Asia continue to differ from global trajectories. Based on these findings, we identify key evidence gaps and outline actionable frameworks that link governance arrangements, financing mechanisms, and equity safeguards to measurable NbS outcomes. Methodologically, the study provides a transparent and reproducible synthesis approach that can be reapplied to track thematic maturation as the literature expands. Overall, the results indicate that while South Asian cities possess strong analytical capacity for NbS, scaling durable, financeable, and socially robust interventions depends on deeper institutional integration within routine urban planning and budgeting. Graphical Abstract Description: The graphical abstract synthesizes the conceptual and analytical workflow of this study, which examines how urban Nature-Based Solutions (NbS) contribute to environmental sustainability in South Asia through a Social–Ecological–Technological Systems (SETS) framework. The left panel outlines the sequential research methodology, beginning with systematic data curation from Scopus (2000–2025) using PRISMA 2020 standards, followed by bibliometric analysis employing VOSviewer and bibliometrix (R) to identify research clusters, keyword co-occurrences, and thematic evolution. The SETS synthesis integrates ecological, technological, and social domains to construct a resilience-oriented analytical framework, culminating in policy translation, where bibliometric insights are aligned with actionable urban governance strategies. The central section visualizes the scaling trajectory of NbS in South Asia, metaphorically depicted through plant growth stages—progressing from fragmented, project-based NbS implementation toward institutional anchoring, governance design, financial security, and equity safeguards. This trajectory represents a transition from analytical maturity to institutional consolidation and social robustness. The right panel conceptualizes NbS impact through SETS interactions, revealing a persistent governance gap and equity neglect despite technological and ecological advancements. Collectively, the figure encapsulates the study’s core argument: that sustainable urban transformation in South Asia requires embedding NbS within integrated SETS-based governance frameworks to achieve measurable resilience, financial viability, and social inclusivity.