Transformation from green to brown: A geospatial analysis of urban expansion, urban heat environment, and agriculture land use conversion

Abstract

Accelerated metropolitan expansion in Global South megacities is increasingly characterised by a green-to-brown transition indicating peri-urban agricultural landscapes transformation into built-up land covers, generating significant pressures on urban thermal conditions. This study investigates how demographic pressure effects land-cover change, growth form, and the Urban Heat Environment (UHE) in Lahore metropolitan. Using Landsat imagery from two benchmark intercensal years (1998 & 2017), land-use/land-cover (LULC) classes were produced through supervised classification, with accuracy assessed through 250 stratified validation points while Land surface temperature (LST) was retrieved from thermal bands. Furthermore, a novel planning-oriented five-zone typology was developed by integrating population density and built-up intensity to distinguish contemporary growth forms such as densification, controlled expansion, sprawl, and residual agriculture land etc. The results demonstrate that the built-up area of Lahore metropolitan has expanded by 140%, which is almost two times than the population growth for same respective years while agriculture cover declines drastically, indicating a footprint-first, leapfrog pattern rather than compact consolidation. Over the same period, the thermal environment has intensified with higher LST aligned to built-up areas and cooler conditions associated with green areas; regression results confirm a strong positive correlation between LST and built-up areas while a strong negative correlation with green cover. Considering the five-zone typology, zone-wise interventions, particularly for Lahore metropolitan, are suggested in this paper ranging from vertical infill in high-density core areas to strict agricultural-preservation zoning to balance Lahore’s urban expansion.