Assessing The Spatiotemporal Urban Green Cover Changes and Their Impact on Land Surface Temperature and Urban Heat Island in Lahore (Pakistan)

Abstract

Urban vegetation has a decisive role in sustaining homogeneous Land Surface Temperature (LST) in a built-up environment. However, urban areas are facing rapid changes in land use/land cover (LULC) over the last few decades as green cover is being replaced by built-up structures. Consequently, LST is increasing and urban heat island (UHI) effects are expanding. In this context, this study was organized to assess urban green cover changes in Lahore and their impact on LST and UHI effects. For this, climate data was collected from the Pakistan Meteorological Department and Landsat images were acquired from Earth Explorer. LULC and LST maps were generated for 1990, 2000, 2010, and 2020 in ArcGIS 10.8. Also, Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI) were computed to analyze the effects of vegetation and built-up areas on LST and UHI. The study found that over the last three decades, built-up area increased 113.85% by removing 392.78 km2 of green cover in the study area. Similarly, a rapid expansion of the high LST range and UHI effects was found towards the eastern and southern parts of the study area. Moreover, a negative correlation was found between LST and NDVI, whereas the correlation between LST and NDBI was found to be positive. Therefore, it was concluded that the continuation of green cover reduction is highly damaging because this might render the city more fragile ecologically. So, the study calls the attention of the responsible authorities for suitable measures against continuous green cover loss in the study area.