Evaluation and Analysis of the Impact of Coastal Urban Impervious Surfaces on Ecological Environments

Urbanization as a human activity alters the surface structure, modifying the urban ecological environment. In this study, the greenness, wetness, building index, and heatness of Dalian, a coastal city in northeast China, were extracted from the summer MODIS remote sensing data of 2010 and 2022, and the remote sensing ecological index (RSEI) was created based on spatial principal component analysis. The artificial impervious surface fraction (AISF) in Dalian was extracted to analyze the impact of urban expansion on urban ecological environment with the background of urbanization, the spatial and temporal change characteristics of the urban ecological environment in Dalian from 2010 to 2022 were thoroughly evaluated. The results show that: (1) Dalian's RSEI in 2010 and 2022 primarily ranged from 0.2 to 0.8. During 2010–2022, the RSEI in urban built-up areas decreased from 0.2–0.4 to 0–0.2. However, the areas of RSEI approaching 1 have increased significantly in the past ten years, mainly distributed in original forest land or ecological land in the northern areas of Dalian. (2) From 2010 to 2022, Dalian's natural environment showed a positive development in which, the area with enhanced ecological quality accounted for 59.09%; however, the proportion of ecological land with RSEI greater than 0.8 declined from 76.64% to 51.05% and the proportion of urban building land rose from 1.11% to 11.85%, demonstrating that urbanization has had a substantial impact on the urban natural environment and has altered the urban land use structure. (3) The AISF of Dalian's urban center area was found to exceed 70% and is centered in the south's densely built-up area. The urban expansion boundary extending from the city center to the surrounding territory has an AISF ranging from 20% to 70%. This study objectively analyzed the geographical and temporal features of the ecological environment, as well as the impact of urbanization, and offers constructive recommendations for urban building design and population distribution optimization.