A Methodology for Quantifying the Spatial Distribution and Social Equity of Urban Green and Blue Spaces

Urban green and blue space (UGBS) contribute to a variety of nature-based values and human health benefits. As such, they play a critical role for the quality of life and sustainability in cities. Here, we use the metropolitan area of Geneva, Switzerland, as a case study to illustrate that UGBS are heterogeneous in spatial characteristics, such as surface area, naturality, or noise levels, which are associated with key cultural ecosystems services. For each characteristic, we defined a threshold with the realization of an associated cultural ecosystem service, including a novel noise threshold (LAeq < 45 dB) compatible with the notion of “quiet”. We then used geospatial information to generate place-based and people-based indicators that collectively describe the variation in key dimensions of UGBS. We found that, in Geneva, the typical (median) resident has access to 4.7 ha of UGBS, and 89% of residents live within 300 m of the nearest UGBS. Accessible surfaces of UGBS per capita, however, were highly variable by type of UGBS and across neighbourhoods. For example, residents from precarious neighbourhoods are less likely to live within 300 m of quiet UGBS than residents of privileged neighbourhoods, and when they do, these UGBS tend to be smaller. The proposed methodology categorizes UGBS in a manner that both captures their distinct social roles and highlights potential social injustice issues.