Quantifying isolation effect of urban growth on key ecological areas

Bin Xun^a,b,c, Deyong Yu^a,c, Yupeng Liu^a,c, Ruifang Hao^a,c, Yun Sun^a,c

^a State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China;

^b Department of Environmental Science, Northwest University, Xi’an 710069, China;

^c Human-Environment System Sustainability (CHESS), Beijing Normal University, Beijing 100875, China.

Abstract: Urbanization may threaten multiple ecosystem processes as well as biodiversity in ecological reserves due to the loss, fragmentation and degradation of habitats in unprotected areas, making it necessary to measure the interference effect of urban growth on the protected areas. This study develops an urban isolation index (UII) to quantify the isolation effects of land-use conversion on key ecological areas (KEAs) and accounts for urban patch size, morphology, location, and quality loss. Based on the five remote sensing Landsat images taken between 1980 and 2005, UII is applied to analyze the spatio-temporal dynamics of the isolation effects caused by rapid urbanization in Shenzhen, China. The results showed that the habitat isolation constantly intensified during the urbanization process. We identified spatially explicit information of critical urban domains that exerted an interference effect on KEAs. There are considerable differences of isolation effects resulting from different urban growth types. Urban edge expansion caused the greatest habitat isolation in Shenzhen. The outlying and infilling urban patches contributed minor isolation effects to the KEAs. This paper furthers the understanding of the ecological effects of urbanization processes and provides a spatially explicit identification for ecological conservation and restoration in rapidly urbanized regions.

Keywords: Urbanization; Ecological restoration; Fragmentation; Urban isolation index; Ecological processes; Landscape ecology.