Urban growth and ecological quality assessment using spatial metrics and RSEI: a case study of Hills Shire council, Sydney, Australia

This study investigates urban expansion and ecological impacts in the Hills Shire, a fast-growing peri-urban area in north-west Sydney, from 2007 to 2025. Using multi-temporal Landsat imagery, Land Use and Land Cover (LULC) maps were created via supervised classification. Urban sprawl was quantified using Shannon's entropy, while landscape metrics such as Class Area, Patch Density, and Edge Density assessed spatial structure. Findings show major conversion of agricultural and natural land into built-up areas, with increasing consolidation and edge complexity. Entropy values rose between 2007 and 2018, then slightly declined by 2025, indicating urban densification. The Remote Sensing Ecological Index (RSEI), incorporating NDVI, LST, wetness, and NDBSI, declined from 0.72 in 2007 to 0.61 in 2025, reflecting worsening ecological quality. Urban heat, reduced vegetation, and habitat fragmentation were key contributors. The study highlights the value of integrating RSEI and spatial metrics into planning to support greener, more sustainable urban development.