Mapping the Global Evidence Base of Urban Green Infrastructure Research: Geographies, Methods and Outcomes

Urban green infrastructure (UGI) has become a prominent organising concept in research on climate adaptation, biodiversity, public health and the equitable provision of ecosystem services. Yet the visibility of an extensive literature does not establish that its geographical coverage, measurement practices or policy implications are equally robust. This critical narrative review maps the structure and evidential reliability of UGI scholarship by integrating bibliometric syntheses, cross-city assessments, field studies, systematic reviews and research on planning and governance. Publications from 1990 to 24 August 2026 were considered, with earlier or foundational conceptual work retained where relevant. Evidence was identified through accessible scholarly indexes, regional research platforms, journal records and citation-based searching, and was appraised for construct validity, geographical representativeness, study design, outcome measurement and transferability. The literature shows substantial convergence on the capacity of well-configured vegetation to moderate local heat, support selected taxa and contribute to stormwater management. Confidence becomes more conditional when claims concern city-wide effects, population health causality, distributive equity, net economic value and durability under climatic change. Bibliometric and thematic maps show that research is increasingly interdisciplinary, but that the locations where evidence is produced, the cities represented in datasets and the places to which recommendations are applied are not equivalent. Remote sensing has extended geographical reach without resolving differences in vegetation quality, access, land tenure or lived experience. Furthermore, green investments may reproduce environmental inequalities when their governance, maintenance and displacement effects are neglected. The review advances an evidence-mapping framework distinguishing research visibility, spatial coverage, causal credibility, social relevance and implementation readiness. It proposes priorities for longitudinal comparative designs, under-represented urban contexts, genuinely multifunctional assessments, and evaluation of who benefits over time. A credible global evidence base requires not only more studies but also better alignment between place, mechanism, measurement and public purpose.