Blue-Green Infrastructure Decline and Thermal Inequality in Siliguri, India: An Intersectional Environmental Justice Analysis (2020-2025)

Purpose – Rapid urban growth in mid-sized Global South cities has intensified surface warming and widened environmental inequities, especially where ecological buffers are fragmented and population pressure is high. This study examines Siliguri Municipal Corporation, a fast-growing Himalayan foothill gateway city in northern West Bengal, India. It quantifies ward-level change in blue-green infrastructure (BGI) and land surface temperature (LST) over 2020 to 2025, models the ecological-thermal association, and evaluates demographic exposure inequality through an environmental justice lens. Design/methodology/approach – The study combines remote sensing, spatial statistics, and demographic overlay within an environmental justice framework. BGI was extracted from ESA WorldCover and Random Forest classification of Sentinel-1 and Sentinel-2 composites, while LST was retrieved from Landsat Collection 2 Level-2 products, both aggregated to the 47-ward scale. Year-wise Pearson correlation and linear regression modelled the BGI-LST relationship, change detection tracked inter-annual coupling, and a composite exposure index combined normalised LST with Census-derived vulnerability indicators to build an integrated ward typology. Findings – A persistent centre-periphery thermal gradient was identified, with wards 6 to 23 and 42 to 46 forming hotspot cores and peripheral wards 30 to 38 retaining stronger ecological buffering. Mean LST rose sharply in 2023 and stayed elevated through 2025, while city-wide BGI fluctuated only modestly. Year-wise BGI-LST correlations ranged from r = 0.09 in 2023 to r = 0.28 in 2025, and regression slopes fell from about 0.98 °C per unit BGI in 2020 to near zero in 2024 before recovering to 0.50 in 2025. The pooled association stayed negative (r = -0.061, slope about -0.41), confirming that BGI-deficient wards recorded higher thermal intensity. The thermal burden coincided with dense populations and vulnerable age groups, indicating structurally unequal heat exposure. Originality/value – The study offers rare ward-scale longitudinal evidence for a mid-sized South Asian gateway city by jointly tracking BGI and LST at a governance-relevant unit and linking ecological deficit with demographic vulnerability in an integrated equity typology. It supports ward-scale heat mitigation through connected green corridors, street-tree networks, peripheral buffer protection, and targeted action in hotspot clusters, providing a replicable template for environmental justice analysis in rapidly urbanising Global South contexts.