Monitoring urban green space for climate-resilient development in the face of rapid urbanization: A tale of two Vietnamese cities

Urban green space (UGS) contributes to sustainable and climate-resilient urban development by providing ecosystem services and enhancing public health. In rapidly urbanizing cities, UGS is compromised by expanding built infrastructure, leading to loss and fragmentation of green areas. This study employs a resource-efficient remote sensing approach for monitoring UGS dynamics in two examples of rapid urbanization, Hanoi and Ho Chi Minh City (HCMC) in Vietnam. The approach identifies UGS by applying a ground-truthed threshold to Normalized Difference Vegetation Index quartile maps (NDVI–P75) from nine years of open-access Sentinel-2 imagery before blending it with national census data. The results indicate a pronounced spatial heterogeneity in UGS distributions, with low densities in urban cores and greater availability in the peripheral districts of both metropolises. The temporal analysis shows diverging trends: while UGS areas in Hanoi are relatively stable overall but declining per capita due to ongoing urbanization, HCMC experiences a general decline in both UGS indicators. The findings emphasize the urgent need for implementing integrated UGS strategies that account for the diverse socio-economic drivers of UGS loss. By offering a robust and reproducible methodology for monitoring UGS, this research highlights the potential of remote sensing tools to inform urban planning and policy development. This approach is highly transferable to other urban contexts globally, demonstrating an effective and transparent pathway to foster climate-justice and “sustainable cities and communities” in line with the United Nations’ Sustainable Development Goal No. 11. • Satellite and census data are used to monitor urban green space in urbanizing cities. • Hanoi and Ho Chi Minh City exemplify how this method reveals spatiotemporal patterns. • The UGS per capita, in both cases, shows gradients between urban cores and periphery. • While both cities face ongoing urbanization, only HCMC shows significant UGS losses. • The presented monitoring approach is robust and readily transferable to other cities.