Assessing long-term urban ecological quality using the remote sensing ecological index: A case study of the Klang River Basin, Malaysia

Many developing countries have experienced rapid industrial and urban expansion over the last two decades, raising concerns about ecological degradation. However, quantitative assessments linking urbanization and ecological quality in tropical developing countries remain limited. This study used the Remote Sensing Ecological Index (RSEI) to evaluate long-term ecological quality in the Klang River Basin, Malaysia, from 2001 to 2023. Landsat imagery and four indicators of greenness, wetness, dryness, and heat were integrated using Principal Component Analysis (PCA) to analyze spatial and temporal changes. Pearson correlation analysis, spatial autocorrelation (Moran's I), and Random Forest–based driving factor analysis were employed to quantify indicator relationships, detect spatial clustering patterns, and identify independent environmental controls. Results show a clear decline in ecological quality over 22 years, characterized by contraction of high-quality zones and expansion of moderate and low-quality areas. PCA and correlation analyses indicate increasing thermal and surface-drying stress over time. However, independent driving factor analysis demonstrates that elevation and hydro-climatic variables provide the primary structural controls on ecological quality distribution, while urbanization intensifies degradation within these constraints. The findings highlight the combined influence of geomorphological structure, climate variability, and urban expansion in shaping ecological change. Integrating remote sensing–based ecological monitoring into urban planning is essential for improving watershed management, protecting forest cover, restoring riparian systems, and enhancing green infrastructure. The study demonstrates the value of RSEI for long-term ecological assessment and provides a framework for linking spatial ecological indicators with sustainable development strategies in rapidly urbanizing tropical basins.