Greening the City with the 3–30–300 Rule: A Spatial Justice Perspective on Housing Governance and Green Gentrification

Urban forestry research increasingly promotes proximity-based benchmarks, such as the 3–30–300 rule, to expand tree canopy, enhance access to nature, and support healthier and more climate-resilient cities. However, a growing body of evidence links green proximity to rising property values and residential displacement, raising concerns regarding green gentrification. These tensions suggest that proximity-based greening cannot be understood solely as an environmental or accessibility intervention; rather, its social outcomes are mediated by the broader housing system. This Perspective argues that the 3–30–300 rule operates as a value-generating urban forestry intervention whose distributive effects are conditioned by housing governance, tenure structures, and the presence of affordability protections. We advance a governance-conditional framework that reconceptualises the rule as a housing-conditioned greening strategy, illustrating how environmental improvements may translate into escalating housing costs and displacement pressures in contexts where housing regulation is weak or fragmented. The analysis highlights the institutional mechanisms through which environmental value is captured, retained, or redistributed across scales, without positing a deterministic relationship between greening and displacement. Aligning urban forestry initiatives with affordability measures and tenant protections is therefore essential if proximity-based greening is to contribute not only to greener and healthier cities, but also to more equitable ones.