History, Progress, and Prospects of Urban Fringe Research in China: An Idiosyncratic Synthesis from a Spatial Perspective

Abstract

Urban fringes, as transitional zones between urban and rural systems, have played a pivotal role in China’s rapid urban expansion. Though there have been very rich urban fringe studies in China, little efforts have been made to introduce this research progress to global peers. To fill this gap, this paper presents an idiosyncratic synthesis based on the relevant Chinese literature, from a spatial perspective—with urban fringes as a land system type of its own kind. We first recap the historical trajectory of urban fringe research in China, revealing its progression from early international influences to context-specific investigations shaped by China’s unique governance and socio-economic conditions. We then introduce, in more detail, the main research progresses on revealing the spatial patterns, underlying mechanisms, and governance practices of China’s urban fringe areas. We argue for studying urban fringes as part of and the critical zone for coupling urban–rural systems, and call for a holistic, inclusive approach in future studies. Specifically, we identify three research prospects: (1) understanding the new patterns of social-environmental dynamics in China’s New Era; (2) promoting spatial governance from a coupled urban–rural system perspective; and (3) leveraging artificial intelligence for producing spatially actionable knowledge.

1. Introduction

With over four decades of economic reform and rapid development, China has expanded its urban footprint dramatically, with an estimated 50,000 square kilometers of urbanized land. The majority of such remarkable urban growth has occurred in China’s urban fringe, which has largely shaped the quality and sustainability of China’s urbanization [1,2]. The term “urban fringe” is also seen in the scholarly literature and governmental documents as urban fringe areas [3], metropolitan fringe areas [4], the urban fringe belt [5], megacity fringe areas [6], the urban–rural interlocking zone [7], and the urban–rural transition zone [8], which have been variously defined. Essentially, the urban fringe describes the transitional area between urban and rural systems—featuring complex physical, economic, and social transformations from the rural to the urban as well as the dynamic landscape mosaic resulting from those intertwined urban–rural interactions [9,10,11].

The dynamic nature of the urban fringe adds significance to its role in shaping the sustainability of China’s urbanization [12]. Prior to 1960, the urban fringe was an integral component of China’s agricultural economy, providing sustenance to China’s small yet growing urban populations [13]. After the 1980s, China’s urban fringe area underwent a fundamental transformation in terms of policy orientation, gradually turning into a region primarily for industrial development across the country and indirectly booming China’s urbanization [14]. In the 1990s, particularly, a vast number of China’s urban fringe areas had developed into known hubs with concentration effects in specific industries like clothing and toys [15]. Contrastingly, since the year 2000, China’s urban fringe has increasingly become a multifaceted and multifunctional zone for developing a more diverse economy and better serving its urbanizing residents [16]. However, in the recent years, there have emerged new and sometimes daunting sustainability challenges across China’s urban fringe areas [10], such as land use conflicts due to urban encroachment [17], social conflicts among diverse residents [18], poor living conditions because of infrastructure underinvestment [19], and growing crimes overwhelming weak governance capacity [20].

Due to the significance of the urban fringe as the frontier of China’s urbanization and the intricacy of the urban fringe as influenced by complex urban–rural interactions, there have been long-lasting scholarly efforts in researching China’s urban fringe since the 1980s. In the Chinese literature, a few reviews of varying depths have been published about the urban fringe, contributing by introducing the relevant international research insights [21], calling for enhancing China’s urban fringe research [22], comparing the international and Chinese literature on the urban fringe [23,24], and synthesizing concepts on the urban fringe [25]. Contrastingly, in the international literature, reviews that systematically introduce the urban fringe research in China are still rare. One exceptional review was published recently, focusing on synthesizing the characteristics of China’s urban fringe areas though [26].

In the above context, this study aims primarily to provide the global peers with the big picture of urban fringe research in China by synthesizing the relevant literature from, particularly, a spatial perspective. Our spatial perspective positions the urban fringe as a land system type with characteristics of its own in sustainable development and contributes to land-based approaches to advancing sustainability through spatial governance and the related human interventions. In this sense, our synthesis focuses on the spatial patterns and processes across China’s urban fringe areas and underlying social-environmental mechanisms, as well as China’s spatial governance practices concerning the urban fringe. The remainder of the paper is organized as follows: Section 2 and Section 3 elaborate on the history and progress of urban fringe research in China, respectively; Section 4 presents some idiosyncratic thoughts on moving the existing research forward to better serve China’s sustainable urbanization; and finally, Section 5 concludes with three notes in relation to the theme of this Special Issue, i.e., “Advancing Sustainability through Land-Related Approaches: Theoretical Foundations and Empirical Investigations.”

2. History of Urban Fringe Research in China

Any long-lasting scientific field must echo the themes of its time. In retrospect, the urban fringe research in China has been influenced internally by China’s rapid and widespread urbanization since the 1980s and externally by pioneering studies in mostly western countries that have a much longer urbanization history. In this vein, meaningful assessment of the urban fringe research in China needs to consider both aspects. We highlight representative terminology and scholars of urban fringe areas. The determination of the representative term is premised upon its first appearance in the published literature. By pinpointing the earliest instances of each term’s use, we are able to trace the historical development of concepts within the field. The selection criteria of representative scholars are centered around their standing and acclaim within the academic community dedicated to this field, as well as the far-reaching citation impact their research works have exerted over time.

2.1. International Context of Urban Fringe Research: From the 1930s to Present

The emergence of the international research on urban fringes dated back to the 1930s when the German geographer Herbert Louis first the concept of urban fringe in 1936. His German studies used the term “Stadtrandzonen” to describe those areas on the outskirts of urban settlements [27]. However, the early root of urban fringe research could trace back to the “garden city” studies by the English urban planner Ebenezer Howard, who made perhaps the first attempt in the late 1890s to plan the landscape transitions from rural to urban [28]. By the late 1990s, more than 500 scholarly articles containing the term “fringe area” had been published in English. These studies covered a wide range of disciplines and yielded substantial findings (Table 1) [2,29]. At the emergence stage, a majority of the scholars focusing on the study of the urban fringe had their roots in geography and landscape ecology [30]. As deeply influenced by the “Age of Exploration”, those emerging research efforts mainly concentrated on revealing the phenomena of land and landscape changes in the urban–rural interface zones, while largely neglecting the underlying processes and mechanisms that drive such changes [14].

The western research on the urban fringe experienced a rapid growth during the 1950s and the 1980s when the world recovered from WWII (World War II) and saw a relatively flourishing economy and associated urbanization. By the late 1960s, scholars had enhanced their investigations on the spatial differentiation of social-environmental elements in urban fringe areas. Such research led to a series of derivative concepts such as “inner fringe areas” and “outer fringe areas”. Meanwhile, studies identified some common features of urban fringe areas, like periodicity, mobility, and relative stability [21,31,32]. The early 1970s witnessed urban fringes receiving new research interests from scholars with background in economics, sociology, and political science. Along with these multi-disciplinary research efforts involving land economics, sociology, demography, and political economy came a new emphasis beyond biophysical space (e.g., economic, social, and power spaces) and associated social-environmental processes within urban fringes [9]. Efforts were then made to explore the spatial patterns, implicit characteristics, and driving mechanisms of growing urban fringes. Relatedly, a series of theories were proposed, such as core–periphery theory, metropolitan structure theory, urban agglomeration structure theory, cyclical mechanism theory, community-driven theory, and commodification-driven theory [33,34,35,36,37,38].

Table 1. The emergence, development, and maturing of international urban fringe research.

Stage	Representative Scholars and Terms	Contents
Emergence stage	Redfield (urban–rural continuum); Wehrwein (rural–urban fringe); R. B. Andrews (rural–urban fringe)	In 1941, Redfield introduced the concept of the urban–rural continuum [39]. Subsequently, in 1942, Wehrwein proposed that fringe areas are transitional zones between clearly defined urban land and agricultural regions [40]. In the same year, R.B. Andrews suggested that the concept of the rural–urban fringe more comprehensively encapsulates the transition zone between urban and rural areas [41].
Development stage	Queen and Thomas (metropolitan region); W. C. Mckain and R. O. Bumight (the inner fringe, the outer fringe); R. G. Golledge (no-man’s region); M. R. G. Conzen (inner fringe, intermediate fringe, outer fringe); E. J. Taaffe and B. J. Garner and M. H. Yeates (suburb); J. W. R. Whitehand (urban fringe belts); R. J. Pyror (rural–urban fringe); L. H. Russwurm (urban fringe)	From the early 1950s to the late 1970s, the formation of fringe areas developed in tandem with the phenomenon of suburbanization. In 1953, Queen and Thomas named this region the metropolitan region and divided this regional structure into three parts, the inner city, the urban fringe, and the urban hinterland, thus pioneering the research on the urban fringe area [42]. W. C. Mckain and R. O. Bumight further refined this by dividing the fringe area into the inner fringe and outer fringe [43]. In 1960, Golledge referred to fringe areas as no-man’s region [44]. That same year, British geographer M. R. G. Conzen introduced the concepts of the inner fringe, intermediate fringe, and outer fringe. He also proposed a cyclical theory, suggesting that the expansion of urban fringe areas undergoes cyclical changes consisting of three phases: acceleration, stasis, and deceleration [45].
		In 1963, E.J. Taaffe, B.J. Garner, and M.H. Yeates proposed an ideal city model, suggesting that an ideal city consists of a concentric structure made up of five parts: the central business district (CBD), the CBD fringe, the intermediate zone, the outer fringe, and the near suburb. The near suburb, composed of industrial, agricultural, and residential areas, is similar to what we refer to as the fringe area [46]. Weisick, on the other hand, defined this area as a “zone of great variation,” due to its random development and mixed land-use patterns [47].
		In 1967, J. W. R. Whitehand conducted research on the issue of locational competition in fringe areas. He emphasized that the planning and architectural forms in fringe zones are just as important as land use patterns, and he referred to these areas as the urban fringe belts [5]. In 1968, R.J. Pryor proposed that fringe areas are zones of land-use transition between urban and rural areas, serving as transitional zones for various elements and characteristics between the city and the countryside, which he called the rural–urban fringe [3]. In 1975, L. H. Russwurm proposed that urban structure should be composed of the core area, fringe area, impact zone, and rural region. He specifically pointed out that the urban fringe area is a continuous continuum between urban and rural areas, heavily influenced by urban radiation. It is a zone where urban development factors penetrate, and land-use transitions occur [48].
Maturing stage	Countryside Commission (Urban fringe)	In the 1970s, the Countryside Commission, through its research reports, emphasized the urban fringe as an important area characterized by the intermingling of urban development, agriculture, and open space [49].

Table 1. The emergence, development, and maturing of international urban fringe research.

Stage	Representative Scholars and Terms	Contents
Emergence stage	Redfield (urban–rural continuum); Wehrwein (rural–urban fringe); R. B. Andrews (rural–urban fringe)	In 1941, Redfield introduced the concept of the urban–rural continuum [39]. Subsequently, in 1942, Wehrwein proposed that fringe areas are transitional zones between clearly defined urban land and agricultural regions [40]. In the same year, R.B. Andrews suggested that the concept of the rural–urban fringe more comprehensively encapsulates the transition zone between urban and rural areas [41].
Development stage	Queen and Thomas (metropolitan region); W. C. Mckain and R. O. Bumight (the inner fringe, the outer fringe); R. G. Golledge (no-man’s region); M. R. G. Conzen (inner fringe, intermediate fringe, outer fringe); E. J. Taaffe and B. J. Garner and M. H. Yeates (suburb); J. W. R. Whitehand (urban fringe belts); R. J. Pyror (rural–urban fringe); L. H. Russwurm (urban fringe)	From the early 1950s to the late 1970s, the formation of fringe areas developed in tandem with the phenomenon of suburbanization. In 1953, Queen and Thomas named this region the metropolitan region and divided this regional structure into three parts, the inner city, the urban fringe, and the urban hinterland, thus pioneering the research on the urban fringe area [42]. W. C. Mckain and R. O. Bumight further refined this by dividing the fringe area into the inner fringe and outer fringe [43]. In 1960, Golledge referred to fringe areas as no-man’s region [44]. That same year, British geographer M. R. G. Conzen introduced the concepts of the inner fringe, intermediate fringe, and outer fringe. He also proposed a cyclical theory, suggesting that the expansion of urban fringe areas undergoes cyclical changes consisting of three phases: acceleration, stasis, and deceleration [45].
		In 1963, E.J. Taaffe, B.J. Garner, and M.H. Yeates proposed an ideal city model, suggesting that an ideal city consists of a concentric structure made up of five parts: the central business district (CBD), the CBD fringe, the intermediate zone, the outer fringe, and the near suburb. The near suburb, composed of industrial, agricultural, and residential areas, is similar to what we refer to as the fringe area [46]. Weisick, on the other hand, defined this area as a “zone of great variation,” due to its random development and mixed land-use patterns [47].
		In 1967, J. W. R. Whitehand conducted research on the issue of locational competition in fringe areas. He emphasized that the planning and architectural forms in fringe zones are just as important as land use patterns, and he referred to these areas as the urban fringe belts [5]. In 1968, R.J. Pryor proposed that fringe areas are zones of land-use transition between urban and rural areas, serving as transitional zones for various elements and characteristics between the city and the countryside, which he called the rural–urban fringe [3]. In 1975, L. H. Russwurm proposed that urban structure should be composed of the core area, fringe area, impact zone, and rural region. He specifically pointed out that the urban fringe area is a continuous continuum between urban and rural areas, heavily influenced by urban radiation. It is a zone where urban development factors penetrate, and land-use transitions occur [48].
Maturing stage	Countryside Commission (Urban fringe)	In the 1970s, the Countryside Commission, through its research reports, emphasized the urban fringe as an important area characterized by the intermingling of urban development, agriculture, and open space [49].

Since the late 1970s, with the Countryside Commission’s thematic symposium on urban fringe research in 1977 as sort of a landmark, global urban fringe research has seen more organized research activities and more cohesive research communities, entering more of a maturing stage [49]. Particularly, since the turn of the 21st century, with sustainability as the new theme of the time, this research field has seemed to be evolving toward a more use-inspired orientation, emphasizing increasingly practical solutions and policy implications. For example, some studies now examine urban fringes in the context of restructuring and transforming urbanization trajectories from monocentric to polycentric patterns [16].

2.2. Two Stages of Urban Fringe Research in China: From Late 1980s to Present

The urban fringe research in China is closely linked to China’s rapid development and urbanization since the reform and opening up in 1978. Nonetheless, it was in the late 1980s that weakly managed urbanization started to bring about various issues associated with urban fringe areas, thus catching governmental and scholarly attention. Back then, the initial urban fringe research in China, like many other research fields in China, was more at an inheritance stage, largely focusing on introducing and applying the ideas, theories, and methods of the western pioneering studies to the context of China [50] (Table 2). However, Chinese studies were featured by their demarcation of urban fringe areas based on usually the official administrative boundaries adopted by the Chinese government instead of the urbanization pattern itself. This, consequently, led to a multiplicity of conceptualizations regarding urban fringe.

Table 2. The inheritance and expansion stages regarding to urban fringe research in China.

Stage	Representative Scholars and Terms	Contents
Inheritance stage	Ministry of Land (urban–rural integration); Chaolin, Gu and Gonghao, Cui (urban fringe); Youqi, Chen (urban–rural interlocking zone); Xueqiang, Xu (urban fringe belt)	In 1987, China’s land and planning authorities first used the concept of the “urban–rural integration” in a series of guiding documents on urban land management, referring to a sub-urban zone emerging in rural areas surrounding cities [51]. From 1989 to 1993, Chaolin, Gu, Gonghao, Cui, Fulong, Wu, and Jin, Wu introduced the term “urban fringe zone” and translated it as “urban fringe area” while studying the fringe spaces of major cities [13,14,52,53]. In 1995, Youqi, Chen, in his published paper, proposed defining the transition zone between urban and rural areas as the “urban–rural interlocking zone” [7]. In 1997, Jianming, Zhang, Xueqiang, Xu, and others, after reviewing over a decade of domestic research on fringe areas, suggested that it should be referred to as the “urban fringe belt” [21].
Expansion stage	Lei, Fan (urban–rural fringe); Xiuqi, Fang (urban–rural transition zone); Wangming, Li, Qifeng, Yuan, and Shidong, Chen (metropolitan fringe); Qingyuan, Yang (metropolitan fringe area)	In 1998, Lei, Fan, based on an analysis of fringe area theory and the development context of the concept, first defined the term “urban–rural fringe” as areas where interactions and mutual influences between urban and rural spaces result in land use, population, and social characteristics displaying both urban and rural features [54]. In 2002, Xiuqi, Fang, based on his study of images of Beijing’s urban area over the past century, proposed the concept of the “urban–rural transition zone,” and argued that this zone is an indispensable part of urban areas [8]. In 2008, Wangming, Li, using the urban fringe area of Hangzhou as a case study, explored the mechanisms behind the decline in ecological carrying capacity from the perspective of ecological carrying capacity and referred to this area as the “metropolitan fringe” [55]. In 2015, Qifeng, Yuan, Shidong, Chen, and others conducted research on the issues of urban–rural integration in the fringe areas, focusing on the peasants and related relationships under rapid urbanization in Guangzhou, and continued to use the term “metropolitan fringe” [56]. In 2015, Qingyuan, Yang introduced the concept of the “metropolitan fringe area” in her study on land use impact in Chongqing’s fringe areas. Metropolitan fringe areas are dynamic transitional zones on the outskirts of large cities, balancing urban expansion and rural transformation with high complexity and diversity [57].

Table 2. The inheritance and expansion stages regarding to urban fringe research in China.

Stage	Representative Scholars and Terms	Contents
Inheritance stage	Ministry of Land (urban–rural integration); Chaolin, Gu and Gonghao, Cui (urban fringe); Youqi, Chen (urban–rural interlocking zone); Xueqiang, Xu (urban fringe belt)	In 1987, China’s land and planning authorities first used the concept of the “urban–rural integration” in a series of guiding documents on urban land management, referring to a sub-urban zone emerging in rural areas surrounding cities [51]. From 1989 to 1993, Chaolin, Gu, Gonghao, Cui, Fulong, Wu, and Jin, Wu introduced the term “urban fringe zone” and translated it as “urban fringe area” while studying the fringe spaces of major cities [13,14,52,53]. In 1995, Youqi, Chen, in his published paper, proposed defining the transition zone between urban and rural areas as the “urban–rural interlocking zone” [7]. In 1997, Jianming, Zhang, Xueqiang, Xu, and others, after reviewing over a decade of domestic research on fringe areas, suggested that it should be referred to as the “urban fringe belt” [21].
Expansion stage	Lei, Fan (urban–rural fringe); Xiuqi, Fang (urban–rural transition zone); Wangming, Li, Qifeng, Yuan, and Shidong, Chen (metropolitan fringe); Qingyuan, Yang (metropolitan fringe area)	In 1998, Lei, Fan, based on an analysis of fringe area theory and the development context of the concept, first defined the term “urban–rural fringe” as areas where interactions and mutual influences between urban and rural spaces result in land use, population, and social characteristics displaying both urban and rural features [54]. In 2002, Xiuqi, Fang, based on his study of images of Beijing’s urban area over the past century, proposed the concept of the “urban–rural transition zone,” and argued that this zone is an indispensable part of urban areas [8]. In 2008, Wangming, Li, using the urban fringe area of Hangzhou as a case study, explored the mechanisms behind the decline in ecological carrying capacity from the perspective of ecological carrying capacity and referred to this area as the “metropolitan fringe” [55]. In 2015, Qifeng, Yuan, Shidong, Chen, and others conducted research on the issues of urban–rural integration in the fringe areas, focusing on the peasants and related relationships under rapid urbanization in Guangzhou, and continued to use the term “metropolitan fringe” [56]. In 2015, Qingyuan, Yang introduced the concept of the “metropolitan fringe area” in her study on land use impact in Chongqing’s fringe areas. Metropolitan fringe areas are dynamic transitional zones on the outskirts of large cities, balancing urban expansion and rural transformation with high complexity and diversity [57].

After joining in the WTO (World Trade Organization) in 2001, China has experienced unprecedented development and urbanization, along with its rapid growth in population, thus leading to remarkably growing urbanization-associated challenges in, particularly, urban fringes. The insufficiency of China’s governance system that was originated from a 5000-year rural history became increasingly prominent, given that China officially turned into an urban society in 2010. Issues at urban fringe areas have gained elevated momentum in the recent years, e.g., inequalities in land utilization, population mobility, and resource allocation [57,58]. These issues are largely rooted in China’s characteristic dual-governance system, with its urban part more of a market economy and the rural part retaining features of a planned economy in many aspects (e.g., rural land use rights cannot be directly traded in the national market except in the few policy pilot areas). That said, these Chinese-featured issues call for more place-based and actionable research, giving the urban fringe research in China more emphases different from those of the western counterpart.

3. Research Progress of Urban Fringe Areas in China

In line with the general pattern of epistemology, existing research on China’s urban fringe areas can be roughly classified into three categories, from the spatial patterns of China’s urban fringe dynamics (i.e., empirical regularities), to their underlying mechanisms (i.e., theoretical rationales), and then, to practical implications (i.e., informed actions). Roughly speaking, the most research output is on the spatial patterns, followed by the practical studies, and last are those mechanistic studies. Increasingly, however, the usefulness of the practical studies relies on a deeper understanding of the social-environmental mechanisms underlying various spatial patterns within urban fringes.

3.1. Spatial Patterns of China’s Urban Fringe Dynamics

From a spatial perspective, urban fringe development is characterized by a transformation of predominantly rural landscapes into a mosaic of urban–rural land uses [9]. To date, the spatial patterns in urban fringe areas remain a topic of substantial research interest. Such research encompasses not only the area’s physical morphology dynamics but extends to its economic, social, and environmental aspects, integrating elements such as land use, industrial activities, social structure, and ecological functioning in a comprehensive manner.

3.1.1. Physical Morphology of Urban Fringe Areas Shaped by Land Use

Urban fringes in China are afflicted with a multitude of land-use conflicts, mainly stemming from the conversion of agricultural land to accommodate urban development [59]. The urban–rural dualistic governance regime of the housing, land, and population registration systems following China’s reform and opening up in 1978 set a starting point for the initial layout of land use in urban fringe areas [60]. During the early 1990s, with the intensification of economic activities, urban fringe areas gradually witnessed land value rises due to spillover from the expanding urban centers. The expansion of built-up areas, accompanied by their encroachment on agricultural lands and the emergence of new mixed-use developments, has shaped the physical morphology of urban fringe areas [61]. In this vein, a considerable number of studies emerged with a focus on the spatial structure and characteristics of the urban fringes around major Chinese cities. Scholars classified the patterns of urban expansion morphology in urban fringe areas into five types, i.e., finger-like, fan-shaped, strip-shaped, scattered-bead, and network, revealing the diversity of empirical regularities of urban development within China’s urban fringes [52,53].

3.1.2. Industrial Evolution in Urban Fringe Areas

Meanwhile, the urban fringe areas in China have been the sites of a sustained and ongoing process of industrial evolution. Following the pervasive implementation of local tax-sharing systems and economic zones in the 1990s, a considerable number of labor-intensive industries were attracted to China’s urban fringe areas due to their relatively lower labor and land costs compared to their urban counterparts [62]. This resulted in a fragmented pattern of land use in urban fringe areas. In accordance with the historical context of industrial expansion and clusters in the 1980s and 1990s, the spatial pattern of the urban fringe underwent a process of differentiation, with the emergence of distinct industrial zones [63]. The subsequent construction of knowledge cities and university towns in the 2000s gave rise to more complex spatial patterns in urban fringe areas. It was accompanied by the conversion of agricultural and rural land into more lucrative residential, commercial, and industrial developments. In recent years, there has been a growing recognition that the spatial layout of the urban fringe has evolved from a concentration of similar industries to a more diverse and mixed-use pattern [64].

3.1.3. Social-Spatial Differentiation Resulting from Social Stratum Segmentation

The social stratum segmentation has been pivotal in shaping the spatial pattern of urban fringe landscapes, which in western countries is known for urban gentrification. In China, a lesser degree of spatial segregation was observed between high-income and low-income populations in urban fringes [65], which impacted the configuration of transportation infrastructures, access to public services, social interaction, and community cohesion [19,66]. Those high-income communities frequently benefited from priority access to public services, housing, and other resources, whereas the low-income communities were constrained to striving for mere survival and development with limited surplus resources. Still, the unequal distribution of resources has resulted in disparate spatial developments. Urban fringe areas were characterized by the clear demarcation of high-end residential neighborhoods from urban villages, giving rise to the formation of distinct social-spatial landscapes. Nonetheless, with the acceleration of urban development and the intensification of social exchanges, there emerged an increasing tendency towards spatial integration in China’s urban fringe areas. The interaction of diverse social groups has contributed to the social-spatial evolution of the urban fringe, from an initially simple urban–rural transition structure to a complex space system. The spatial distribution of residences, consumption patterns, and employment situations among various social classes has been continuously adjusted over time. This has propelled the spatial processes within urban fringe areas to develop in a more diversified and inclusive manner [67,68].

3.1.4. Green Space and Degraded Ecosystem Functioning in Urban Fringe Areas

Large-scale and spatially continuous green spaces have long been a prominent feature of China’s urban fringe areas. However, during the last few decades, the rapid urban expansion has led to substantial changes in ecological patterns and the degradation of ecosystem functions in urban fringes [69]. In this regard, the conversion of agricultural land into built-up areas has severely disrupted food production. Moreover, the encroachment onto wetlands and forested areas has given rise to the weakening of water yield, the loss of flooding control, and the destruction of wildlife habitats. Given the increasing recognition of the complex interplay between urban growth and environmental integrity, the focus of urban fringe studies has shifted towards various examinations of urbanization-associated eco-environmental impacts, particularly through landscape ecological perspectives [70,71]. Studies have identified the most typical landscape ecological patterns observed in China’s urban fringes, i.e., concentric, scatter, network, and radial structures. Thereinto, the concentric layout depends on the configuration of forest and water bodies that encircle urban land, thereby forming a separation belt between urban and rural landscapes. The network layout is primarily composed of interconnected ecological nodes ad corridors. Such elements contribute to safeguarding the integrity of ecological landscapes and guaranteeing long-term benefits. The radial pattern is determined by a complex combination of natural conditions and transportation routes, while the scatter layout is shaped by the distribution of ecological patches [72,73].

3.2. Spatial Mechanisms Underlying China’s Urban Fringe Dynamics

As documented in most studies, the drivers of urban fringe dynamics in China are a blend of economic growth, industrial development, transportation infrastructure optimization, rural–urban migration, and government policies [74]. Among these multifaceted drivers, rapid economic development is a prerequisite for the expansion of urban fringes. Since the late 20th century, extensive research has been dedicated to exploring the relationship between urbanization processes and urban expansion. This discourse has emerged in the context of urban centers confronting the challenges of economic structure adjustment and industrial upgrading. Manufacturing sectors have been compelled to relocate to urban fringe areas due to the urban hinterland’s demand for large residential, commercial, and public service spaces [75]. Consequently, there was a noticeable rise in the conversion of agricultural land to industrial land in urban fringes. Meanwhile, the construction of the transport network has improved connectivity between the core areas and the surrounding suburbs [14]. Certain factories that were heavily reliant on transportation had a concentrated and spatially continuous development pattern along the main roads and/or rivers in the inner parts of urban fringes. Shanghai is among the most striking instances of urban fringe expansion primarily due to economic drivers. The establishment of industrial zones in urban fringe areas was proposed in the Shanghai Master Plan in 1959 [76,77]. It described how the exploding population would be navigated to the urban fringe during different periods and presented the layout of the “inner edge belt” (Figure 1a). From 1959 to the 1970s, industrial clusters in the urban fringe areas of Shanghai started to form, integrating industrial parks with residential zones. Following this period, satellite towns including Minhang, Wujing, and Songjiang progressively emerged and experienced development. These strategic plans played a crucial role in maintaining a well-organized industrial layout while effectively curbing the uncontrolled expansion of the urban boundary. Moving into the 1980s and thereafter, the overcrowding phenomenon in central Shanghai became increasingly pronounced. Consequently, portions of the population shifted away from the central urban area. This shift necessitated ongoing investments in the infrastructure and public services of the urban fringe areas. Such efforts have significantly contributed to the development of the city’s multi-center spatial structure. Especially with the expansion of the industrial activities in the planned areas of Jinshanwei and Wusong-Baoshan, a large amount of agricultural land was transformed into industrial land. As an integral part of the environmental enhancement project initiated in recent years, these regions underwent a further transformation into land dedicated to the development of eco-friendly chemical industries, business operations, tourism-related undertakings, and information technology-based activities. Over the past several decades, the proportion of developed land in the urban fringe of Shanghai has reached 66% [78]. In a sense, Shanghai pioneered in the decentralization of industrial activities from the urban core to the fringe.

The phenomenon of rural–urban migration has also been widely acknowledged as a crucial factor in the evolution of urban fringes. On one hand, the expansion of industrial activities in the urban fringe promoted a significant influx of migrants from rural regions [80]. The employment opportunities to rural migrants and the possibility of their turning into urban household registration were especially attractive [81]. On the other hand, urban residents in pursuit of spacious living conditions and exhibiting sensitivity to housing prices congregated in urban fringe areas [58]. The migration of populations to urban fringe areas further stimulated the development of residential settlements, public infrastructure, and traffic networks.

Moreover, governmental interventions at various levels regarding land use, urban planning, and infrastructure investments exert a decisive influence on the trajectory of urban fringes [82]. In contrast to the largely bottom-up processes in urban fringes of western countries, the expansion of the urban fringe in China represents a strong top-down feature driven by diverse policy interventions [83]. The development of transport and infrastructure networks is a central policy tool for governing urban fringes. Local governments offer tax incentives, subsidies, and other financial benefits within industrial zones targeting the urban fringe as a way to bridge economic disparities. In addition, the establishment of new urban centers in urban fringe areas has been regarded as an avenue for facilitating technological innovation. One of the primary examples of how governance and policy drive the transformation of an urban fringe area into a pivotal node of urban expansion is the Tongzhou district of Beijng City (Figure 1b) [79]. The strategy of relocating government functions and constructing a national capital sub-center in Tongzhou district prompted the outward migration of the original inhabitants from the older urban areas to the originally fringe areas. Supported by the planning of residential, commercial, and industrial spaces, Tongzhou has now become a hot spot for immigration and investment. The population growth facilitated industrial upgrading, with policies encouraging the development of high-tech industries replacing traditional manufacturing. At the same time, rapid urban expansion led to significant changes in land use, particularly, the reduction in farmland and green spaces. These shifts, while boosting economic vitality, also intensified ecological challenges, such as increased air pollution and strain on water resources, showcasing the trade-offs of policy-driven urban transformation.

3.3. Spatial Governance of China’s Urban Fringe Areas

It is of paramount importance to ensure the orderly utilization of land resources in urban fringes. The land use within the urban fringe is characterized by the expansion of developed areas, the accelerated non-agricultural transformation, and alterations in the agricultural structure [84]. Along with China’s remarkable economic success in the past few decades, the Chinese government has also made notable progress in advancing its governance capacity, which also applies to their management of urban fringes. The urban–rural dualistic land tenure system enables the Chinese government to intervene in regional land use through systematic planning and management endeavors. In this regard, farmland protection is a long-standing policy objective, which is achieved through the demarcation of conservation areas (i.e., “farmland redline”) and the execution of requisition–compensation balance measures [85]. In addition, the location of industrial zones has been planned by taking into account both the convenience of transportation and the potential environmental repercussions. Moreover, to enhance land-use efficiency and expand the scale of agricultural operations, a series of land reform initiatives have been initiated in rural areas, such as the intensified management of land resources and the transfer of land contractual rights [86,87]. These policies have exerted recognized impacts on China’s urban fringe dynamics.

In the recent years, the Chinese government has made more spatial governance efforts for improving environmental sustainability, which used to receive insufficient attention. In this regard, the eco-environment in urban fringes is highly vulnerable to human activities, and thus, both central and local governments have formulated various policy interventions. These measures range from the imposition of strict land-use regulations to the execution of ecological restoration projects. They also involve the establishment of green belts and wildlife corridors for the protection of biodiversity in urban fringes. Specifically, the Ecological Redline policy represents a sustainability bottom line (similar to the Farmland Redline) aimed at curbing unregulated urban sprawl and strengthening the protection of natural elements [88]. Additionally, public participation initiatives have been increasingly launched to deal with environmental issues [89]. For example, the establishment of public-friendly platforms allows the public to report environmental violations, while also cultivating environmental awareness and promoting green lifestyles among residents [90].

Last but not the least, the effective planning and management of public open spaces in urban fringes is considered as a way of enhancing the well-being of local residents. However, public open spaces in urban fringe areas face challenges of relatively chaotic development and limited functionality. With the rapid expansion of the built-up environment in urban fringes, illegal occupations of public open spaces occur frequently. Unfortunately, the governance responsibilities concerning public open spaces are currently scattered among relevant departments. It has been posited that the governance of public open spaces should be based on effective coordination and regular supervision [91]. Another proposal is to promote a community-based participatory approach given that public open spaces are not just physical entities but integral components of community life [92]. This approach is beneficial for sustaining the natural landscape of public open spaces considering the diverse interests of the various stakeholders in the urban fringe. Overall, a balance between protection and utilization is needed regarding public open spaces in urban fringe areas.

4. Research Prospects Toward Sustainable Urbanization in China’s New Era

4.1. Differences in the Urban Fringe Research Between China and the West

Although the central concerns within the realm of urban fringe research in China and the West share commonalities, there are distinct variances in the objects of investigation as well as the methodologies. In China, research on urban fringe areas typically focuses on the land-use changes during the urbanization process, the ambiguity of the urban–rural demarcation, and the resultant spatial governance challenges. In recent years, scholars have explored the coupling relationship between land development and tenure in urban fringe areas, as well as the role of administrative spillover effects in the spatial governance of these areas, through methods such as structural equation modeling [93,94]. In contrast, urban fringe research in Western countries lays more emphasis on the impacts of urban sprawl on society, the economy, and the environment [95]. Especially under the backdrop of globalization and urbanization, issues such as the “leapfrog” expansion of cities and the livelihoods of residents in fringe areas are of great concern [96]. In some developed countries, research regarding urban fringe areas also involves the construction of diversified ecological networks, aiming to mitigate the negative impacts of urban expansion on ecosystems.

Yet another significant difference in the urban fringe research between China and the West lies precisely in the choice of research methods. Chinese scholars tend to employ quantitative methods, such as remote sensing technology and spatial analysis, to explore the evolutionary process of urban fringes and changes in land use [97]. In contrast, western research more frequently uses the case-study method, by combining multidisciplinary perspectives from sociology, geography, and ecology to analyze the interrelationships among social dynamics, environmental changes, and land use in urban fringe areas [98].

Overall, with the advancement of globalization, there are likely to be more intersections in future research on urban fringe areas between China and the West, especially in terms of how to achieve sustainable development and coordinated urban–rural development.

4.2. Understanding New Patterns of Social-Environmental Dynamics Across China’s Urban Fringe Areas in the New Era

The phenomenon of urban fringes and its characteristics evolve with time. The dynamism and complexity of urban fringes will intensify or diminish depending on societal development needs. It is imperative to reexamine the dominant development challenge within China’s urban fringes in the post-2012 New Era with new norms of economic development, urbanization trends, and political tendency, among many other aspects. For a long period of time after China’s reform and opening up, the officially identified dominant development challenge to China is “the contradiction between Chinese people’s ever-growing material and cultural demands and the backward social production [99].” As China officially declared its entering the New Era of socialism with Chinese characteristics in 2012, the dominant development challenge was re-identified as “the contradiction between Chinese people’s ever-growing needs for a better life and inadequate, unbalanced development [100].” In such a context, it is expected that China’s urban fringes would present, in the upcoming few decades, new patterns different from those that have been studied.

For example, environmental sustainability is currently one of the inadequately developed dimensions across China at large and, similarly, in its urban fringes [101]. Unlike in foreign countries, China’s urban fringe development has been predominantly driven by economic factors and industrial activities [25], thereby resulting in more adverse impacts on the environmental system. Luckily, in the past few years, there has been a significant push towards ecological restoration initiatives in China’s urban fringes. These initiatives, such as the greening of wastelands and the enhancement of water systems, are designed to rehabilitate damaged or degraded habitats that have been affected by previous urban fringes expansion and development activities [102]. Consequently, future policies for developing urban fringes in China may see more integration of President Xi Jinping’s idea of ecological civilization with economic, social, political, and cultural development.

For another instance, to address the unbalanced development issue, which will likely remain a long-lasting challenge facing China’s urban fringe areas, future policies may prioritize developing areas currently underdeveloped, e.g., fringe areas of the small and medium sized cities, fringe areas of the shrinking cities [103], and unique cultural landscapes within a fringe area. Particularly, there are rich cultures deeply rooted in urban fringe areas with promising prospects for the development of tourism and cultural industries [13,104]. Recent studies have shown that through the introduction of diverse commercial activities, cultural exhibitions, and comprehensive services, some of those traditional villages are undergoing revitalization. Meanwhile, this gives rise to a wide range of employment opportunities and prompts the return of the indigenous population to the urban fringe villages [105]. Therefore, the new policy norms of urban fringe development in the New Era calls for timely research on potentially new patterns of environment- and balance-oriented development activities.

4.3. Promoting Spatial Governance of China’s Urban Fringe Areas from a Coupled Urban–Rural System Perspective

The urban fringe is initially defined as the transitional zone between urban and rural areas, long studied as a “side” product of studying the urban core [106]. After many years, the urban fringe has now been recognized in China as a research unit of its own kind for advancing sustainability. Yet, from a meta-coupling sustainability perspective, it is still insufficient. Urban fringe areas, while presenting unique social-environmental patterns and facing unique development challenges, are closely coupled with the rural and urban subsystems. It is the coupled urban–rural system instead, rather than the urban fringe (or the rural/urban), that makes a meaningful governance unit of sustainability. For example, the planning and building of an ecological network of green spaces for an urban–rural system would be more appropriate than for, merely, the urban fringe. In other words, sustainability governance at the landscape/regional or above scale makes more sense.

The spatial governance of China’s urban fringe areas from a coupled urban–rural system perspective, as elaborated by Tan et al. (2024) in this Special Issue, involves not only the various stocks of social-environmental elements (e.g., labor, resources, capital), but also the uni-/bi-directional flows of social-environmental interactions (e.g., migration, ecosystem services, trade), as well as the overall functional complementarity between heterogeneous spatial units (e.g., agriculture-oriented, environment-prioritized, urban-oriented) [107]. Urban fringe areas are the bridging zones between the rural and the urban, and thus, at the core of diverse elements, flows, and functions [108]. In the sustainability community, it is often advocated to “think globally, plan regionally, and act locally.” Yet, for the spatial governance of China’s urban fringe areas in the future, the most challenging may be the transboundary governance as a coupled urban–rural system, which involves different administrative units, and each may have its own socio-political architecture and policy agenda.

The good news is that there has been more and more transboundary spatial planning explored in China, e.g., metropolitan area planning and watershed planning [109,110,111]. However, an inclusive sustainability blueprint benefiting the whole urban–rural system is far from sufficient. The “dirty” work for realizing such cooperation interests lies in effective coordination between vertical and horizontal governments and among the government, society, and market. Sustainability is not an end, but a journey. Such muti-agent coordination in various action arenas and situations for the spatial governance of coupled urban–rural systems remains an underexplored task. In this regard, insights from political sciences, public administration, and public policy, such as polycentric governance, collaborative governance, and adaptive governance, may provide complementary actionable knowledge in addition to the existing planning-centered literature and practices [112,113].

4.4. Leveraging Artificial Intelligence for Producing Spatially Actionable Sustainability Knowledge

Another missing point in the existing Chinese literature on the urban fringe is how to leverage artificial intelligence for producing actionable sustainability knowledge. We are now in an era with more and more freely available geospatial big data, which are improving toward better spatiotemporal resolutions [114]. Such improved data in combination with better big-data models has shown encouraging promises in areas including but not limited to high-resolution monitoring, predictive modeling, and real-time decision making while studying various land system types or landscapes in general, though barely regarding urban fringe areas.

In terms of high-resolution monitoring, the landscape, population, and other social-environmental dynamics across various urban fringe areas or even nature can now be better mapped based on integrating big earth data via platforms like Google Earth Engine. Better data and better models are more inclined to produce better maps. Similar studies have been published on mapping global urban land, national wetland, and forests, and even on monitoring progress toward the United Nation’s Sustainable Development Goals [115,116,117].

In terms of predictive modeling, the capability of artificial intelligence to fuse socioeconomic data (e.g., census records, infrastructure databases, transportation network information) with environmental data (e.g., climate variables, soil quality, biodiversity hotspots) would better capture the often non-linear and complex social-environmental interactions, thus producing more accurate modeling predictions. Similar studies are very rich now, for instance, the GeoSOS-FLUS model (http://www.geosimulation.cn/FLUS.html, accessed on 20 October 2024) [118,119]. Following these studies, thematic predictive models may be developed with tailored model modules for capturing urban fringe processes.

In terms of real-time decision making, it is not methodologically challenging to employ artificial intelligence algorithms on continuously updated streams of sensor data to create interactive, real-time dashboards in areas like transportation and disaster risk management [120,121]. However, for applications in urban fringe research, an additional issue is how to integrate the existing methodological practices with citizen science and participatory decision making. In this regard, ethical and transparent digital governance seems especially understudied.

5. Concluding Notes

So, how does our study contribute to advancing sustainability through land-related approaches? The above synthesis reveals a somewhat “narrow-minded” research landscape on the urban fringe in the Chinese literature—one that focuses on the spatial patterns and underlying mechanisms of urban land expansion across China’s urban fringe areas and that relates to sustainability mostly concerning the various unsustainable outcomes of such urban land expansion. We argue that the urban fringe is a land system type featuring a complex adaptive social-environmental system of its own kind, distinctive from the urban and rural counterparts that it couples with. Such an up-to-date understanding of the urban fringe per se should serve the purpose of better understanding and governing the multidimensional spatial tradeoffs and synergies of the coupled urban–rural system with land/space as an entry point and intervention instrument.

It is a prerequisite to explore the new patterns or long-term trends of land-use changes and associated social-environmental dynamics across China’s urban fringe areas. We identify that the issue of environmental sustainability has become particularly prominent in urban fringe areas. Integrating the collaborative strategies of ecological restoration and land development in the urban fringe areas could be an innovative direction in the future.

The spatial governance of China’s urban fringe areas from a perspective of coupled urban–rural systems remains an underexplored task. An inclusive sustainability mindset calls for producing spatially actionable knowledge to adaptively balance the multidimensional outcomes of urban expansion and associated landscape dynamics in the urban fringe and its coupled urban and rural systems.

Moreover, the blossoming artificial intelligence technologies have introduced growing opportunities that could enhance data analysis, predictive modeling, and decision-making processes toward more effective spatial governance efforts, which have remained underrecognized.

To this end, we urge scholars, practitioners, and policymakers to collaboratively reconceptualize China’s urban fringe areas—not as peripheral zones of unchecked growth, but as pivotal landscapes where strategic research, inclusive governance, and cutting-edge technologies converge—to transform these areas into catalysts for sustainable urbanization. We would like to propose embracing a more inclusive mindset in future research on China’s urban fringe areas, with our sincere hope to advance multi-scale spatial governance of the urban fringe toward sustainable urbanization in China’s New Era.