Does the biodiversity of urban green spaces impact on human health? A systematic review of literature.

Green spaces and their biodiversity seem to improve the urban life quality. However, a wide range of descriptors were associated with multiple health outcomes, which limits the comparability of existing evidence. The objective of this systematic review was to organise this knowledge, investigating the relationship between biodiversity in urban green spaces and health outcomes in adults. Following PRISMA guidelines and a registered protocol (PROSPERO: CRD42025636281), a search of PubMed, Scopus, Web of Science identified studies published between January 2014 and July 2025. The search strategy ("biodiversity" AND "human health" AND "urban green space") yielded 147 eligible studies. Most were published between 2017 and 2020 (57%) and predominantly relied on medium-sized cohorts of 101-10,000 participants (55%). Health outcomes fell into four categories: (i) general health, mental health, and well-being; (ii) drug prescriptions; (iii) chronic diseases (cardiovascular disease, T2 diabetes, obesity); and (iv) birth outcomes. Green exposure was primarily assessed through vegetation-based indicators: 66.1% of studies used green-exposure metrics (tree canopy or vegetation cover), 34.0% NDVI, and 22.4% percentage green area. Only a minority incorporated composite ecological indices or fauna-based metrics (bird or insect richness). Across all health domains, findings were predominantly favourable. Between 70% and 90% of studies on general health, mental health, and well-being reported beneficial associations with green exposure, including improved self-rated health, reduced depressive and anxiety symptoms, lower stress, and increased life satisfaction. All studies using drug prescription data found inverse associations between green exposure and antidepressant or anxiolytic prescriptions. Evidence for chronic diseases consistently indicated protective associations: reduced cardiovascular and respiratory disease risk, prevalence of T2 diabetes, and all-cause mortality. Birth outcomes demonstrated more variability, with half of the studies reporting positive associations, largely influenced by socioeconomic and contextual factors. Socioeconomic status frequently modified associations, with stronger positive effects observed among lower-SES populations. The overall evidence indicates that richness of urban green spaces is associated with health benefits. However, the role of biodiversity remains unclear and understudied, mostly due to inconsistent measurements and ambiguous associations with health outcomes. Integrating ecological quality into urban planning may therefore represent an important strategy for promoting healthier and more equitable urban environments.