Urban nature-based solutions as public-health infrastructure: a scoping review of implemented interventions.

Urban nature-based solutions (NBS) are increasingly promoted as tools to make cities healthier, more climate-resilient and more equitable, but most reviews still rely on observational studies of greener versus less green neighbourhoods. This scoping review examined implemented urban NBS and blue-green infrastructure (BGI) (such as parks, greenways, blue-green corridors, vegetated barriers and wetlands) that were evaluated using quantitative designs measuring either health outcomes or health-relevant environmental exposures. Findings were organised using the three-pathway model of Markevych et al. (2017): restoration, instoration or behavioural activation, and mitigation of environmental exposures. Primary studies with evaluative or quasi-experimental design were searched in PubMed, including randomized trials, controlled before-after, difference-in-differences, and controlled field measurement. Eleven studies were included, results were summarized narratively, and risk of bias was assessed qualitatively using design-specific domains. Evidence from recent field and quasi-experimental studies reveals three complementary pathways through which NBS influence health. First, structured exposure programs in urban forests and parks produced consistent improvements in stress, mood, anxiety and, in some cases, sleep. Second, landscape-scale interventions such as greenways, canal restorations and large new parks were associated with increases in walking and cycling, better perceived safety and, at city level, narrower mortality or childhood overweight gaps between areas. Third, NBS designed for environmental protection reduced heat, airborne pollutants and potentially pathogenic microbial loads, demonstrating a protective function. Τhese findings indicate that urban NBS can operate as active public-health infrastructure. However, the evidence base remains small, with limited long-term follow-up and few studies linking environmental change directly to clinical outcomes. Future work should integrate health monitoring into NBS design to support evidence-based urban policy. Limitations include restriction of the search to PubMed and the absence of direct clinical outcome measurement in four included studies.