Spatiotemporal assessment of urban environmental livability in Dhaka (2004–2024)

Rapid and largely unplanned urbanization has significantly reshaped Dhaka over the past two decades. This transformation has accelerated environmental degradation, reduced green and blue spaces, and undermined urban livability in one of the world's most densely populated megacities. Despite these growing environmental challenges, comprehensive long-term spatial assessments that integrate remote sensing and multi-criteria decision-making approaches remain scarce. This study assesses the spatiotemporal dynamics of urban environmental livability in Dhaka for 2004, 2014, and 2024 using the Urban Environmental Livability Index (UELI). Six indicators, including the Normalized Difference Vegetation Index (NDVI), Wetness, Index-based Built-up Index (IBI), Night Light Index (NLI), Urban Heat Island Ecological Intensity Index (UHIEII), and Air Pollution Index (API), were derived from multi-sensor remote sensing datasets in Google Earth Engine (GEE). Principal Component Analysis (PCA) and the Fuzzy Analytic Hierarchy Process (FAHP) were employed to determine indicator weights, while Global Moran’s I and Local Indicators of Spatial Association (LISA) were used to analyze the spatial distribution and clustering of UELI. The findings reveal a substantial decline in environmental livability, with livable areas decreasing from 30.53% in 2004 to 26.87% in 2014 and further to 20.75% in 2024. In contrast, unlivable areas expanded from 15.65% to 17.84% and 30.80% over the same period. Notably, approximately 24.69% of Dhaka’s total area transitioned to an unlivable state between 2004 and 2024. One-at-a-Time (OAT) sensitivity analysis and Partial Rank Correlation Coefficient (PRCC) analysis with a 95% confidence interval confirmed the robustness of the UELI framework and highlighted the dynamic nature of urban-environment interactions. Spatial analysis further identified the central and southwestern parts of Dhaka as the most affected areas, exhibiting the greatest deterioration in environmental livability and ecological conditions. The study provides robust empirical evidence to support sustainable urban planning, informed policy formulation, and effective urban ecological risk mitigation in rapidly urbanizing cities.