Urban Expansion and Environmental Change: Impacts on Land Surface Temperature, NDVI, and Air Quality in Kolkata Municipal Corporation

The expansion of cities has changed land use/land cover (LULC) and intensified the urban heat island (UHI) effect. This has happened because of the large use of asphalt and increased concretization. Therefore, it is very important to examine the relationship of urban growth of cities and consequently the Land Surface Temperature. In this paper, these phenomena have been analyzed from 2003 and 2025 in Kolkata Municipal Corporation. Multi-temporal Landsat satellite data (LANDSAT-5 and 8) have been used. In addition, this study analyzes the correlation of LST with increase in the concentration of key air pollutants (NO2, SO2, PM10) and resulting AQI values for Kolkata. To measure land transformation, LULC classification and NDVI were analyzed quantitatively. Landsat data were processed through single-channel and single-window algorithms for LST retrieval. The LULC classifications have an overall accuracy of more than 85% and 0.85 as the value of Kappa coefficient. There has been a significant increase in the percentage of built-up area from 41.71% in 2003 to 75.80% in 2025 and decreases in the amount of vegetation cover from 49.52% in 2003 to 20.12% in 2025 were found. The maximum LST in KMC increased substantially from 32.45°C in 2003 to 40.98°C in 2025, which is a serious concern. Comparatively, the AQI for Kolkata has been in decline since 2003, with PM₁₀ being the predominant contributor to the increase in AQI. The NO₂ levels show partial decreases but retain strong seasonality in peaks, while SO₂ levels increased moderately. Overall, the trend of these pollutants has increased in the Kolkata Municipal Corporation. The findings show a strong association among urban expansion, loss of vegetation and rising heat stress. There is an urgent prerequisite of planning of rapidly growing cities like Kolkata for the sustainable future.