China has experienced fast urbanization over the past three decades. Growth in the economy was steady due to reform and policies designed to open the economy, as well as globalization. Additionally, China experienced an explosive population increase in urban areas. The urbanization rate increased from 17.6% in 1978 to 56.1% in 2015 [1
]. An increasing population and urbanization resulted in a rising demand for housing. As a consequence of reformations to the land and housing system since the 1990s, aggressive, large-scale, low-density, and non-continuous development of housing real estate was widely implemented in urban fringes and suburbs [2
]. It led directly to a high level of residential land use fragmentation (defined as continuous areas of residential landscape changed into smaller, more isolated patches), characterized by irregular patch shapes, varying patch sizes, and dispersed arrangement between patches [5
Land use fragmentation has been one of the most noticeable problems in the accelerated urbanization context of China. Before the 1980s, almost all urban land was administratively controlled and operated by the central government, and the transfer of urban land was prohibited [6
]. Early in this period, residential estates were commonly built and organized in the form of “Dan wei”, and primarily concentrated in the urban centers. Later, as the open market for urban land was established [3
], local governments could earn large revenues from selling land to investors for large-scale real estate projects at the urban fringes and suburbs, causing severe landscape fragmentation. As a result, a series of negative effects on urban development associated with land use fragmentation emerged, such as deteriorated ecosystems [7
] and low efficiency of land use [9
]. In recent years, scholars have extensively discussed the phenomenon in which land use fragmentation in urban areas is posing pressing challenges in societies that use land-planning [11
Most landscape fragmentation studies concentrate on patterns and dynamics analysis [10
]. Landscape metrics, regarded as a common approach, are used to quantify landscape structures and patterns in the study of landscape ecology [19
]. However, because they had the primary goal of identifying the composition patterns of different land use types within the ecological landscape, these studies tended to treat built-up areas as a single homogeneous element, along with other elements, such as farmland [20
], forest [23
], and green space [25
]. Thus, residential land use, as a component of urban built-up areas, was rarely discussed from the perspective of fragmentation. In fact, residential land accounts for a large proportion of urban expansion, and is the leading component in the expansion and change of urban built-up areas [11
], whose fragmentation level is closely related to compact urban development.
This paper examines the fragmentation of residential land use and the underlying mechanisms within the urban built-up area of Nantong city in the Yangtze River Delta region, using a multi-spatiotemporal perspective with the aim to provide the aforementioned missing information, and provide implications and suggestions for the improvement of residential land use planning in response to rapid urbanization. Based on residential land use data derived from a series of land use maps of the built-up area from 1994 to 2015, the spatiotemporal patterns of residential land use change and its dynamics were quantified using landscape metrics and multivariate linear regression. Through this approach, we aim to discover whether there are general trends of residential-land fragmentation corresponding to urbanization, analyze the fragmentation pattern and the driving forces behind it, and provide decision support for residential land use planning and managing practices.
The rest of the study is organized as follows: Section 2
describes the study area, and the source and processing of data. Section 3
illustrates the results of landscape pattern analysis and regression analysis. Section 4
discusses the spatiotemporal patterns and dynamics of residential land use fragmentation and provides policy implications. Section 5
draws conclusions based on the results and discussion.
This paper explored the spatiotemporal changes in landscape patterns in residential land use, and offered quantitative insights into exploring the dynamic mechanisms of residential land fragmentation in Nantong city with its rapid urbanization from 1994 to 2015. In light of the compact development goal and the increasingly strict control of urban land expansion, this paper can be regarded as a timely assessment of residential land use fragmentation, and can be applied as guidance for residential land use planning and management practices. We used landscape metrics to analyze the residential land use data derived from Nantong’s land use maps, and applied multivariate linear regression to quantitatively explore the driving factors behind the process of Nantong’s residential land use fragmentation. We found that Nantong has experienced rapid residential land expansion and spatial imbalance among the three districts by referring to the values of PLAND from 1994 to 2015.
Metric analysis has quantified the spatiotemporal features of residential land use fragmentation in Nantong. The results reveal distinct temporal fluctuation and spatial differentiation in Nantong’s residential land use fragmentation. On the one hand, there is a close relationship between fragmentation level and urbanization stages. On the other hand, two general trends of spatial changes in residential land use fragmentation were found: a scattered form of residential development with a low density in the newly established zones will lead to the increase of fragmentation, and a contiguous form of residential development with a high density in the urban center can decrease fragmentation.
The results of the regression analysis revealed that the rapid increase in the tertiary industry had the most noticeable impacts on residential land use fragmentation in Nantong. In the context of socio-economic transition, Nantong’s residential land use fragmentation is also closely related to the dynamics of the land market and government policies.
With the orientation of compact land use in China, “compact city” will be the future mode of Chinese city development [11
], which means that consolidating fragmented construction land patches in the core areas and increasing the development density, as well as optimizing the various types of construction land use, especially residential land use, is crucial. In this sense, fragmentation metrics can be used as good planning assessment tools to provide a timely, ecologically oriented approach to assess construction land use. Furthermore, this approach has the advantage of matching the fragmentation level to the administrative territories. Thus, socio-economic data and governance bodies can be linked directly and clearly to explore the driving factors underlying it, which is more constructive when developing more accustomed local planning and management policies.