Tracking green space along streets of world cities

Abstract

Street green space (SGS) - the presence of vegetation along streets of cities - is an increasingly relevant indicator for sustainable cities. SGS provides a set of local services such as mitigating the urban heat island effect and reducing the impact of extreme precipitation events, while it is also associated with increasing human well-being. Here we present a global analysis of recent trends in SGS based on modelling a street-based indicator of vegetation density (the Green View Index, GVI) with high-resolution multispectral satellite data and additional granular data. Estimating local to continental trends between 2016-2022 based on 190 large cities distributed across seven macroregions, we find that globally SGS has decreased by almost two percent. Statistically significant changes in city-level median SGS (p<0.01) are found in approximately one-quarter of the cities analysed. However, the direction and magnitude of trends both show a high level of heterogeneity between regions, which we explore by assessing SGS inequalities within each city. Our analysis provides an updated picture of SGS across world cities and an open-source, validated approach to assess its future changes in near real-time and support the design of policies for greener cities.