Tracking green space along streets of world cities

Abstract Street green space (SGS) - the presence of vegetation along streets of cities—is a key piece of urban infrastructure. SGS provides a broad range of functions, such as mitigating the urban heat island effect, reducing the impact of extreme precipitation events, and supporting human and animal well-being. Here we introduce an approach to estimate SGS based on the statistical modeling of a street-based indicator of canopy coverage (the green view index, GVI) with multispectral satellite observations and ancillary spatially granular data. Based on our trained and cross-validated non-parametric model, we conduct spatial sampling and prediction in 190 large cities distributed across twenty regions and estimate local to continental GVI trends between 2016–2023. Jointly considering such global pool of cities, we find evidence of a trend of GVI decrease of 0.3%–0.5% per year ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>p</mml:mi> <mml:mo>&lt;</mml:mo> <mml:mn>0.01</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> . Yet, both the direction and magnitude of trends show high heterogeneity across and within regions and cities, which we explore, along with stark inequalities in SGS availability within each city. Our analysis provides an updated estimate of the GVI as a measure of SGS across a global pool of cities and an open-source, validated approach to assess its future changes and support the design of policies for sustainable cities.