Spatio-temporal changes of green spaces and their impact on urban environment of Mumbai, India

In the context of rapid urbanization and climate change, urban green spaces significantly contribute to mitigate the subsequent increasing urban heat island (UHI), particularly to reduce the increasing land surface temperature (LST), aridity and intensity of heat waves through their cooling effects in the surrounding areas. The gradual depletion of urban green spaces, largely due to increasing population pressure and urban expansion, has resulted in the land use land cover change (LULC) and has altered the micro-climate of the urban ecosystem. In this context, the present study has analysed and assessed the changing scale and spatial layout of the urban green spaces using the landsat thematic mapper (TM) and OLI/TIRS remote sensing image data from 1988 and 2018 in Mumbai city. Multiple correlation matrix analysis of LST and NDVI, with 200 sample sites of Mumbai, has been carried out to demonstrate how the LST of green space has been changed to other LULC over the period of three decades. The assessment using various indices like LST, normalized difference vegetation index (NDVI), land surface emissivity (LSE) and leaf area index (LAI) indicated that there has been drastic transformation of urban green spaces; it has reduced from 46.42% in 1988 to 26.67% in 2018. The areas of LST higher than 30.50 °C have dramatically increased from 5232 ha in 1988 to 14,339 ha in 2018. The expanding urbanization has engulfed half of the dense vegetation having > 0.3 NDVI index; it has reduced from 17,406 ha in 1988 to 9910 ha in 2018. Since declining green spaces is a negative indicator to the environment, the policy makers, planners and legislation should emphasize and adopt measures to restore green areas of the Mumbai metropolitan region.