The Spatiotemporal Pattern of Urban Expansion in China: A Comparison Study of Three Urban Megaregions

Abstract

Urban megaregions have emerged as a new urbanized form. However, previous studies mostly focused on urban expansion at the city scale, particularly for large cities. Understanding urban expansion at the regional scale including cities having different sizes is important for extending current knowledge of urban growth and its environmental and ecological impacts. Here, we addressed two questions: (1) How do the extent, rate, and morphological model of urban expansion vary at both the regional and city scales? (2) How do factors, such as city size and expansion rate, influence urban expansion models? We focused on the three largest urban megaregions in China, Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD). We quantified and compared the spatiotemporal pattern of urban expansion during 2000-2010 at both the regional and city scales based on remote sensing data. We used correlation analysis and linear regressions to address our research questions. We found that (1) the three urban megaregions experienced rapid and massive urban growth, but the spatiotemporal pattern varied greatly. Urban expansion was dominated by edge-expansion in the BTH, edge-expansion and infilling in the YRD, and infilling in the PRD. Cities in the same megaregion tended to have similar expansion morphology; (2) geographical location influenced the model of urban expansion the most, followed by city size and by its expansion rate. Small-sized cities were more likely to develop in a leapfrogging model, while cities with relatively rapid expansion tended to grow in an edge-expansion model.

Spatial distribution of urban greenspace in response to urban development from a multi-scale perspective

“…The domain of infilling type of urban growth within cities suggested that the nine major Chinese cities became more compact in terms of spatial growth models. This result was consistent with findings from previous studies that some of the Chinese cities became more compact through infill development (Yu and Zhou 2017). In this study, we only focused on urban expansion in core areas of cities considering the consistency of ecosystem services provision in these densely populated zones.…”

“…However, the four medium-sized cities still experienced the loss of large patches. Such difference was likely due to the cities being in different phases of urban growth (Deng et al 2008, Yu andZhou 2017).…”

Effects of Urban Expansion on Forest Loss and Fragmentation in Six Megaregions, China

“…In contrast, the correlations between the proportional cover of developed land and the mean patch size of forested land was no longer significant in the BTH and WH megaregions after controlling for the patch density of developed land, indicating that the impact of spatial pattern of developed land is more important in the BTH and WH megaregions. The different roles of patch density on forest fragmentation might be related to the differentiated morphological types of urban expansion in different megaregions [40,42,50,51], as dispersed urban expansion can lead to increased forest fragmentation [42,50]. For example, the PRD was dominated by expansion of infilling, the YRD was dominated by infilling and edge-expansion, and the BTH had the highest proportion of edge-expansion from 2000 to 2010 [40].…”

“…The different roles of patch density on forest fragmentation might be related to the differentiated morphological types of urban expansion in different megaregions [40,42,50,51], as dispersed urban expansion can lead to increased forest fragmentation [42,50]. For example, the PRD was dominated by expansion of infilling, the YRD was dominated by infilling and edge-expansion, and the BTH had the highest proportion of edge-expansion from 2000 to 2010 [40]. It would be interesting to examine the effects of different types of morphologies of urban expansion (e.g., leapfrogging, edge-expansion, and the infilling) on forest fragmentation in future studies.…”

“…We used two indices to measure the magnitude and relative speed of urban expansion in the six megaregions, by following the method in [26,[38][39][40]. The area of newly-developed land (Equation (1), A new ) was used to measure the magnitude of urban expansion.…”