Assessing Spatiotemporal Changes (2013–2025) in Ecological Quality Using RSEI: Stability and Urban-Core Improvement in Hangzhou, China

As a newly designated international wetland city, Hangzhou (China) is currently exploring pathways for high-quality, sustainable development as a habitable city. It is necessary to reveal the baseline status of ecological quality scientifically and rationally whilst tracing its historical changes to support future detailed urban development planning. This study employs the GEE platform, utilizing remote sensing images of Hangzhou from 2013 to 2025. The RSEI index is constructed using four indicators directly perceptible to humans: dryness, heat, wetness, and greenness. The RSEI, coefficient of variation, and Sen-trend analysis were applied to evaluate patterns in ecological quality changes within Hangzhou. Results indicate that during the study period, Hangzhou exhibited minimal variation in RSEI values and Sen indices, reflecting overall ecological stability. Areas classified as “good” ecological grade increased, while other grades decreased. Ecological improvement primarily occurred in early-developed central districts like Xihu and Gongshu, demonstrating Hangzhou’s commitment to refined urban ecological management. This study validates the feasibility of RSEI for environmental assessment in Hangzhou, effectively guiding the city’s pursuit of refined development during late-stage urbanization to enhance the residents’ well-being. Furthermore, it provides a case study for ecological and environmental monitoring in megacities with similar characteristics to Hangzhou, offering significant demonstration value and implications.