[H-TT15] Geographic Information Systems and Cartography

[HTT15-10] Three Decades of Urbanization: Impacts on Greenspaces and Population Access in Global Cities (1990-2020)

★Invited Papers

*Ahmed Derdouri¹, Yuji Murayama¹, Takehiro Morimoto¹ (1.Institute of Life and Environmental Sciences, University of Tsukuba)

Keywords:Urbanization, Greenspace, Population Exposure, Global cities, Land use dynamics

This study analyzed land use and land cover (LULC) changes, greenspace distribution, and population exposure to urban greenspaces (UGS) from 1990-2020 across four Global North (GN) cities (Berlin, Phoenix, Sydney, Tokyo) and four Global South (GS) cities (Casablanca, Riyadh, Cape Town, Mexico City). The methodology involved satellite imagery collection and processing, LULC classification and UGS extraction, and assessing human exposure to UGS, using Landsat imagery, population data (GHSPop, WorldPop), and urban boundaries to inform the analysis. Supervised classification and spatial modeling approaches were utilized to analyze LULC transition dynamics, characterize greenspace profiles across cities, and assess population-weighted greenspace exposure levels over time. Results showed notable increases in impervious surfaces (IS) across all cities, correlated with urban expansion. GN cities exhibited slow growth of 0.4-0.7% per year except Phoenix with a faster urbanization rate (1.9% per year). GS cities showed more rapid expansion of 1.1-2.4% per year. This occurred largely at the expense of UGS, with decreases of 0.13-0.37% per year in GN cities and up to 1.22% per year in Casablanca. The analysis of LULC transition dynamics revealed the dominance of IS to UGS conversions over the reverse. Furthermore, cross-sectional greenspaces’ profiles from city centers indicated general maintenance or slight decreases in GN cities, but mixed patterns were observed in GS cities. Exposure analysis showed radius-dependent increases in population greenspace exposure, but fluctuations over time. Overall, the study demonstrates significant IS expansion and losses of UGS across global cities, with faster rates occurring in GS cities. It also highlights the complex spatiotemporal dynamics of UGS distribution and exposure, emphasizing the need for strategic greenspace planning, especially in rapidly developing cities.