Lifeng Shi

Urban expansion in China and its spatial-temporal differences over the past four decades

The urban expansion process in China from the 1970s to 2013 was retrieved based on remote sensing and GIS technology. With the latest zoning method used as reference, annual expansion area per city, urban expansion type, and fractal dimension index were employed to analyze the Chinese urban expansion characteristics and its spatial difference from the aspects of urban expansion process, influence of urban expansion on land use, and urban spatial morphological evolutions. Results indicate that 1) under the powerful guidance of policies, urban expansion in China went through six different stages, and cities in the eastern region entered the rapid expansion period the earliest, followed by cities in the central, northeastern and western regions; 2) cultivated lands and rural settlements and industrial traffic lands were the important land sources for urban expansion in China; the influence of urban expansion on land use in the eastern region was the strongest, followed by the central, northeastern and western regions; 3) urban spatial morphology tended to be complex and was directly related to the adopted spatial expansion mode. Infilling expansion became the main urban expansion mode in the western region first, then in the central and northeastern regions, and finally in the eastern region. This study establishes the foundation for an in-depth recognition of urban expansion in China and optimization of future urban planning.

Spatial differences of coastal urban expansion in China from 1970s to 2013

As the ‘economic engines’ of China, coastal cities have developed and expanded considerably since the 1970s. In this study, information on the urban expansion process of Chinese coastal cities from the 1970s to 2013 was retrieved. Through the analysis of stage characteristics, spatial expansion modes, influences on land use, centroid shifts, and spatial morphological evolutions, the spatial differences of coastal urban expansion were revealed. Results indicate that 1) the expansion stages of southern coastal cities are more complex than those of northern coastal cities, and the expansion ranges and speeds of the former are far higher than those of the latter; 2) the spatial expansion of southern coastal cities mostly adopt a single mode, whereas northern coastal cities mostly adopt a mixed mode; 3) significant spatial differences in the occupations of different land sources exist between the south and the north along the coastline; 4) the centroid of coastal cities tends to migrate toward the coastline, and the centroid shift distances of southern coastal cities are clearly higher than those of northern coastal cities; and 5) the spatial morphology of southern coastal cities tends to be compact, whereas that of northern coastal cities tends to be loose. Policies have a powerful significance in terms of guiding urban expansion and its spatial differences in coastal cities. Urban expansion in coastal cities will encounter new opportunities and challenges under the guidance of new types of urbanization strategies.

Extraction of basic trends of urban expansion in China over past 40 years from satellite images

If urban sprawl is to be avoided in China in the next ten years, it is not only crucial to understand the overall history, current status, and future trends of urban expansion there, but also these differences, and this is presently lacking. In this study, remotely sensed images with approximately 30 m spatial resolution were used to quantitatively assess the spatial and temporal patterns of urban expansion of 60 Chinese cities (1973–2013). Urban-expansion-process curves of the cities studied were drawn using annual expansion area as an indicator. Curve similarity analysis generated four basic process modes of urban expansion in China. These included cities that: 1) peaked around 2004 and then decelerated; 2) peaked around 2010 and then decelerated; 3) showed sustained acceleration, and 4) showed continued deceleration. Four basic process modes represented cities under different levels of development stage. Geographic location was found to be the most related characteristic to urban expansion process. Regional development policies at the national level in each region also showed highly temporal consistency with fluctuation characteristics of urban expansion process. Urban characteristic such as population size and administrative level were not found to be significantly related to urban expansion-process modes. Understanding the basic process-mode categories well is extremely important for future regional-balance planning and development of macroeconomic policies.

Urban expansion in China and its effect on cultivated land before and after initiating “Reform and Open Policy”

Urbanization in China has expanded at an unprecedented speed since the declaration of “Reform and Open Policy” and presented many challenges. Unbalanced regional development, appearance of super megacities and concomitant problems, and conflicts between urbanization and cultivated land protection are three critical problems that Chinese urbanization has to face. To develop new plans for foreseeable future urbanization in China, it is critical to understand the evolving history of cities across China. This study maps urban expansion of 60 typical Chinese cities based on large amount of remote sensing data and the labor-intensive image interpretation method, in order to understand the history of urban expansion from the 1970s to 2013. Results showed that area of cities expanded 5.23 times compared to their area in the 1970s. Urban expansion in China accelerated three times (1988–1996, 1999–2006, and 2009–2011) and decelerated three times (1997–1998, 2007–2008, and 2012–2013) over the 40 years. The urban area of South China expanded most significantly 9.42 times, while the urban area in Northeast China expanded only 2.37 times. The disparity among different administrative ranks of cities was even greater than (3.81 times) the differences among different regions. Super megacities have been continuously expanding at a fast rate (8.60-fold), and have not shown obvious signs of slowing down. The proportion of cultivated land among the land sources for urban expansion decreased to a small extent in the 1990s, but cultivated land continues to be the major land source for urban expansion. Effective future urbanization needs controlling the expansion scale of large cities and reasonably developing medium and small cities, as well as balancing regional development.

Urbanization in China from the end of 1980s until 2010 - spatial dynamics and patterns of growth using EO-data

ABSTRACT Urbanization in China has been experiencing a remarkable dynamism in the past 40 years. The most evident implication of urbanization is the physical growth of cities. We analyze urban land growth rates and changes in spatial urban forms from the end of the 1980s to 2010 based on the authoritative National Land Use/Cover Database of China. We present new spatial measures that describe ‘urban land growth types’ and ‘fluctuations in urban land growth’ within the monitoring time span with a temporal interval of five-year steps. We evaluate the correlations between urban land growth rates and socioeconomic data. Results show that (1) distinct characteristics exist on the spatiotemporal evolutions of urban land growth rates in terms of area and perimeter, e.g. coastal areas exhibit the most dramatic growth rates; (2) the spatial distribution characteristics of ‘urban land growth types’ and ‘fluctuations in urban land growth’ follow similar spatial patterns across China, e.g. significant differences exist between the eastern region and other regions; and (3) a moderate correlation exists between urban area growth rate and urban population growth rate at an R² of 0.37. By contrast, we determine no significant correlation between urban area growth rate and tertiary industry value growth rate.

City size distribution and its spatiotemporal evolution in China

Based on the National Land Use/Cover Database of China (NLUD-C) in the end of the 1980s (the 1980s, hereafter), 1995, 2000, 2005, and 2010, 665 cities were selected to study the size distribution and its changes of urban lands in China. In this study, the spatiotemporal evolutions of urban land size distribution as well as the influence of administrative-level on these cities were explored by combining urban spatial positions and administrative-levels. Results indicate that: 1) City size distribution using urban lands was more practical and reasonable than using non-agricultural population. 2) In the 1980s, cities with ascending urban land rank were centralized in Eastern China, specially the Changjiang (Yangtze) River Delta, the Zhujiang (Pearl) River Delta, and Beijing-Tianjin-Hebei region. Cities in Central, Western, and Northeast China mainly indicated descending urban land rank. 3) The transfer of national development focus resulted in cities with ascending urban land rank becoming evenly distributed nationwide; however, this trend was slightly centralized around Chengdu, Chongqing, and Wuhan in different periods. 4) During the 1980s to 2010, the proportion of cities with ascending urban land rank in provincial capitals, municipalities, and special administrative regions (high-level cities, hereafter) was consistently higher than those in prefecture- and county-level cities except for 2005–2010. The ranks of the majority of the prefecture- and county-level cities were mainly descending, supported by ascending; the proportion of cities with unchanged rank is small. This study breaks through the bottleneck of traditional research in the area of city size distribution by examining urban land replacing the non-agricultural population. The current study also provides scientific explanation for the healthy and reasonable development of urban land as well as the coordinated development of population urbanization and land urbanization.

Evaluating Urban Expansion of Beijing during 1973-2013, by Using GIS and Remote Sensing

This paper presents an integrated study about the urban expansion process in Beijing from 1973 to 2013. Annual urban expansion area index, gravity center transfer model, fractal dimension index and the elastic coefficient or urban expansion-population growth are employed to explore the temporal and spatial characteristics of urban expansion. The results reveal that urban expansion of Beijing underwent seven different expansion stages, including one slow and steady expansion stage, three fast expansion stages, three shot deceleration stages, in the past 40 years. The centroid of urban lands moved to the southeast and urban boundaries became more and more complex and irregular. Urbane expansion speed was not harmonized with population growth distinctly in 1987-1998, 2000-2003 and 1998-2000. This study can provide scientific data for urban planning of Beijing and related studies of urban expansion in depth.

Monitoring Urban Expansion and Morphology Changes of Tangshan by Using Remote Sensing

On the basis of multi-source satellite data on compact ratio, fractal dimension and barycentric coordinates across different periods, we analyze the spatiotemporal characteristics and morphology changes of Tangshan using geographical information system and remote sensing techniques. The speed of urban expansion slowed down from 1976 to 1996 and changed periodically from 1996 to 2013. The variation trend of the compaction index is contrary to that of the fractal dimension. The changes in the compaction index showed a downward trend, and the fluctuations were reduced after 1996. Meanwhile, the variation trend of the fractal dimension is exactly the opposite of that of the compaction index, which showed an upward trend and experienced an increase in fluctuations after 1996. The barycenter of the built-up area of Tangshan moved toward the northeast from 1976 to 2009 and turned southwest from 2009 to 2013.

Urban Expansion in China Based on Remote Sensing Technology: A Review

Urban areas and its evolution are important anthropogenic indicators and human ecological footprints, and play decisive roles in environmental change analysis, global geo-conditional monitoring, and sustainable development. China has the highest rate of urban expansion and has emerged as an urban expansion hotspot worldwide. In this paper, the progress of studies on Chinese urban expansion based on remote sensing technology are summarized and analyzed from the aspects of urban area definition, remotely sensed imagery applied in urban expansion, monitoring methods of urban expansion, and urban expansion applications. Existing issues and future directions of Chinese urban expansion are discussed and proposed. Results indicate that: 1) The fusion of multi-source remotely sensed imagery is imperative to meet the needs of urban expansion with various monitoring terms and frequencies on different scales and dimensions. 2) To guarantee the classification accuracy and efficiency and describe urban expansion and its influences on local land use simultaneously, the combination of visual interpretation and automatic classification is the tendency of future monitoring methods of urban areas. 3) Urban expansion data have become the prerequisite for recognizing the urban development process, excavating its driving forces, simulating and predicting the future development directions, and also is conducive to revealing and explaining urban ecological and environmental issues. 4) In the past decades, Chinese scholars have promoted the application of remote sensing technology in the urban expansion field, with data construction, methods and models developing from the quotation stage to improvement and innovation stage; however, an independent and consistent urban expansion data on the national scale with long-term and high-frequency (such as annual monitoring) monitoring is still lacking.

Urban expansion modes of major cities in China in the past four decades

Urban lands of Chinese cities tend to expand in an unreasonable way, which has been a critical problem for China due to its insufficient land resources. As the important carrier loading active social economic activities and dense population, municipalities and provincial capitals are in an important strategic position in the China. In this study, 4 municipalities and 27 provincial capitals are selected as the study objects, and Urban Expansion Type index (UET, hereafter) is employed to quantitatively analyze the spatial-temporal characteristics of the urban expansion mode in these 31 sample cities. Results indicate that (1) in the past four decades, edge-expansion was the primary urban expansion mode in municipalities and provincial capitals, and infilling and leapfrog modes were the secondary and the third modes, they had contribution rates of 73.16%, 24.00% and 2.84 to urban expansion, respectively. (2) 56.86%, 42.69% and 0.45% patches of increased urban lands appeared in edge-expansion, infilling and leapfrog modes, respectively. (3) In six periods, increased urban lands in edge-expansion mode increased dramatically first and then decreased gradually, while presenting a dramatically increasing trend and fluctuated change trend in infilling mode and leapfrog mode, respectively. (4)The area and number of patches converted from non-urban lands to urban lands in three modes all had some close correlation, especially the infilling mode.