Assessing Interannual Urbanization of China’s Six Megacities Since 2000

Abstract

As a large and populous developing country, China has entered the rapid urbanization stage since 2000. Until 2018, China has accounted for nearly 1/5 of global megacities. Understanding their urbanization processes is of great significance. Given the deficiencies of existing research, this study explored the interannual urbanization process of China's six megacities during 2000-2018 from four aspects, namely, the basic characteristics of urban land expansion, expansion types, cotemporary evolution of urban land-population-economy, and urbanization effects on the local environment. Results indicated that (1) urban lands in China's six megacities increased by 153.27%, with distinct differences across megacities; (2) all of six megacities experienced the expansion processes from high-speed to low-speed, but they varied greatly in detail; (3) the speeds of urban land expansion in China's megacities outpaced the population growth but lagged behind in GDP increase; and (4) urbanization has triggered an environmental crisis, which is represented by the decline in vegetation coverage and the increase in land surface temperature in newly expanded urban lands. This study enriched the content of urbanization, supplemented the existing materials of megacities, and provided a scientific reference for designing rational urban planning.Despite conducting denser social activities and causing more drastic urban sprawl effects than other medium-and small-sized cities [9], megacities must face more serious eco-environment problems, such as air pollution [10,11], flood disaster [12,13], and cropland losses [14], which have been proven to reflect the urbanization characteristics of a country or region better [15].Urbanization hotspots are expected to emerge in developing countries in the next several decades of the 21st century [1]. As a large and populous developing country with nearly 1/5 of the megacities worldwide, China has experienced significant urbanization at an increasing rate of 232.48% since the implementation of the Reform and Opening-up Policy in 1978 and the country has entered into the rapid expansion stage since 2000 [16]. Therefore, China is a good research area for investigating the urbanization process. During the past decades, urban expansion in China has been thoroughly investigated by using remote sensing technology. These studies have identified the following features. (1) Research objects ranged from a single city (i.e., Beijing [5], Shanghai [17], Harbin [18], Guangzhou [19], Nanjing [20], etc.) to urban aggregations (i.e., Beijing-Tianjin-Hebei [21], Pearl River Delta [22], Yangtze River Delta [23], etc.). However, limited investigations have been conducted on China's six megacities.(2) Research approaches included but not limited to various classification models (i.e., supervised or unsupervised classification, artificial neural network, etc.) and analysis methods (i.e., spatiotemporal dynamics, sprawl patterns, etc.). However, urbanization is a comprehensive process involving both physical morphology and ...

Assessing 40 years of spatial dynamics and patterns in megacities along the Belt and Road region using satellite imagery

“…For instance, AGRs of megacities in Asia and Africa were greater than those in Europe, which was consistent with Taubenböck's conclusions (Taubenböck et al 2012). Besides, several existing studies proposed that urban expansion and population increase could be affected by natural terrain and transportation (Yu, Zhang, and Liu 2019;Yu et al 2019a). As its strong standpoint, this study found that inland megacities showed a 'mononuclear and concentric circle' expansion mode, whereas the coastal ones expanded according to a 'bidirectional and narrow shape' mode ( Figure 3).…”

“…During the past several decades, the economic and cultural exchanges in this region have created special conditions for the formation and expansion of local cities. Surpassing other types of cities in both inhabitants and physical size, the megacity is regarded as an important city form that reflects national urbanization characteristics (Liu et al 2016;Yu et al 2019a). Concentrating nearly 60% of global megacities, the B&R is undoubtedly an appropriate region for researching the urbanization processes of megacities.…”

“…of a city, and focused on the expansion forms, directions and environmental effects (i.e. Kuang et al 2014;Yu et al 2019a). Among these studies, research on spatiotemporal characteristics and patterns can provide basic information and references of understanding the urbanization processes.…”

Spatial Evolution of Urban Expansion in the Beijing–Tianjin–Hebei Coordinated Development Region

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