Spatiotemporal Analysis of Urban Expansion and Its Impact on Agricultural Land Degradation and Vegetation Health in Narayanganj District, Bangladesh

Urban expansion, driven by rapid population growth, has increasingly encroached upon agricultural land and contributed to the degradation of ecological systems.In this study, the spatiotemporal dynamics of urban growth in Narayanganj District, Bangladesh, were assessed over a 20-year period (2003-2023) using integrated Geographic Information System (GIS) and remote sensing techniques.Land Use and Land Cover (LULC) changes were quantified, and their ecological consequences were evaluated through vegetation indices including the Normalized Difference Vegetation Index (NDVI) and the Soil-Adjusted Vegetation Index (SAVI), alongside the Normalized Difference Built-up Index (NDBI).An LULC classification revealed a net increase of 5.61% in built-up areas, accompanied by reductions of 7.61% and 1.61% in barren land and agricultural land, respectively.The spatial pattern of urban expansion was found to be uneven, with pronounced growth observed from the northern to northnorthwestern sectors of the district.A two-phase conversion analysis indicated that 15.68% of agricultural land was transformed into urban areas between 2003 and 2013, followed by a slightly lower conversion rate of 14.74% from 2013 to 2023.Notably, a statistically significant inverse correlation was detected between NDBI and both NDVI and SAVI, suggesting a measurable decline in vegetation health associated with urban intensification.These findings provide empirical and geographically grounded evidence of the adverse ecological impacts of urbanization in a peri-urban context.The integration of multi-temporal satellite images with vegetation and built-up indices enabled a comprehensive evaluation of land transformation processes and their environmental implications.The insights gained from this research may inform sustainable land use planning, urban policy formulation, and conservation strategies aimed at mitigating the loss of agricultural land and safeguarding vegetation health in rapidly urbanizing regions.