Impact of urban expansion on ecosystem services in different urban agglomerations in China

Urban expansion has greatly impacted ecosystem services (ESs), with each stage of urbanization having a specific role in altering them. Exploring how urban expansion influences ESs are critical for generating guidelines for urban planning and improving the development of urban agglomerations (UAs). However, previous studies have lacked analyses of urban expansion and its association with ESs in UAs in China. In this study, we analyzed year-by-year land-use data from 1992 to 2015 and explored the impact differences of urban expansion on ESs using a Tobit regression model. The results revealed that urban-land area showed a continuously increasing trend in UAs during the study period. Especially after 2000, a more pronounced increase in urban-land area and urban expansion intensity index was detected. Simultaneously, the ecosystem services value (ESV) showed a sharp reduction. Forestland had the highest sensitivity coefficient ranging from 0.496 to 0.505. Moreover, we found that counties with a high urban expansion differential index gradually showed in areal UAs and exhibited a clustered feature in northwest China. Additionally, high-average ESV counties were mainly distributed in the periphery of the UAs. In general, urban expansion had a negative impact on the ESV in all UAs, except for the Northern Tianshan Mountain UAs. The West Taiwan Strait, Jinzhong, and Pearl River Delta UAs were most affected by urban expansion, with the proportion of urban land increasing by an average of 1%, and the ESV decreasing by 0.77%, 0.75%, and 0.73%, respectively. In contrast, the Dianzhong UAs was the least affected. This study indicates the need for a better control of the scale and speed of urban expansion, especially for UAs whose ESVs were greatly affected by it.