Bryer and colleagues examine greenspace not through a single outcome but through an umbrella review of 36 systematic reviews and meta-analyses published between 2010 and 2020. The key intellectual contribution lies in refusing a uniformly beneficial narrative: mortality, mental health and cognitive function show broadly favourable associations, while cardiovascular, metabolic, respiratory, general-health and quality-of-life outcomes remain more ambivalent, and much of the underlying review literature carries low-to-moderate methodological quality and high risk of bias. Their methodological operation is therefore double: synthesize a very large evidence field while auditing the quality of the syntheses themselves. This exposes the gap between policy enthusiasm for greenery and the uneven epistemic strength of different health claims. The wider bridge is to evidence-based urbanism: greenspace can be treated as public-health infrastructure only when exposure measures, outcome definitions, causal assumptions and review quality remain visible rather than being compressed into a generic claim that “green is good”.