Urban landscapes are complex and ever-evolving entities, shaped by a diverse array of social, economic, and environmental forces. In recent years, Chinese cities have witnessed significant shifts in their spatial development patterns, presenting challenges and opportunities for sustainable urban growth. Groundbreaking research by Hu, Y., Hu, T., Xue, F., and colleagues published in npj Urban Sustainability in 2026 provides a comprehensive examination of one critical phenomenon affecting urban morphology in China: the fragmentation of built-up areas. This study delves deeply into the mechanisms behind changing urban forms, highlighting a shift from predominant edge expansion to intensified infilling activities at the core of urban fabric.
Historically, Chinese urban growth has been characterized predominantly by edge expansion, where cities sprawl outwardly by extending their boundaries into peri-urban and rural zones. This radial expansion was driven largely by population increases, industrialization processes, and robust infrastructure development aimed at accommodating emerging economic hubs. However, as land availability becomes increasingly scarce in metropolitan peripheries and policies seek to curb uncontrolled sprawl, the nature of urban growth is transitioning. The research underscores that infilling—developing vacant lands within existing urban areas—now plays an increasingly central role in reshaping city layouts. This transition holds profound implications for urban fragmentation.
Urban fragmentation refers to the breaking down of contiguous developed spaces into smaller, disconnected patches. Such fragmentation disrupts the integrated functioning of urban environments, often leading to inefficiencies in land use, transportation challenges, and deficiencies in public service delivery. Hu et al. provide a nuanced perspective, revealing that fragmentation in Chinese cities is not a mere byproduct of random growth patterns but rather an outcome shaped by institutional policies, economic incentives, and infrastructural constraints. These forces collectively alter the spatial logic behind urbanization, transitioning the dominant spatial growth form from edge-centric expansion to more complex scenarios involving infilling.
A fundamental driver behind this fragmentation is the heterogeneity in land-use regulations across municipalities and regions. Different administrative areas exhibit varied capacities for land conversion and development intensities, creating a patchwork of opportunity zones within urban boundaries. The study highlights how local governance structures, which differ widely in China due to its decentralized governance framework, stimulate or inhibit infilling development to different degrees. As a result, urban cores experience differentiated densification rather than uniform growth, leading to increased fragmentation at micro and meso scales.
At the infrastructural level, limitations in transportation networks also catalyze fragmentation. The research indicates that existing transport corridors often favor specific nodes, prompting concentrated infilling around certain high-accessibility locations while neglecting others. This spatial imbalance magnifies fragmentation by creating pockets of high-density development surrounded by underutilized or vacant lands. Moreover, the expansion of mass transit systems and the prioritization of transit-oriented developments are poised to influence this pattern further, emphasizing focused growth corridors that reinforce fragmented configurations.
Economic transformation, particularly the shift from traditional manufacturing bases toward service-oriented and high-tech industries, exerts a significant influence on urban form as well. As employment clusters relocate closer to urban cores or specialized zones, infilling is increasingly stimulated to accommodate these new economic functions within existing built-up areas. This, in turn, fosters spatial heterogeneity and parcelization of land uses, fragmenting the urban fabric as diverse land uses vie for space within confined boundaries.
In addition to physical and economic forces, socio-demographic dynamics contribute to fragmentation. Increasing urban population heterogeneity, including migration patterns and socio-economic disparities, shapes housing demand in complex ways. High demand for affordable housing in central locations induces developers to fill in vacant lots aggressively. However, this rapid infilling often occurs sporadically, producing irregular urban patches amid formerly continuous neighborhoods. The fragmentation manifests not only spatially but also socially, with enclave formations and segregated communities altering urban cohesion.
Environmental considerations play another essential role in the observed trends. Chinese urban policy increasingly emphasizes ecological sustainability and green space preservation. Regulations aimed at protecting environmental amenities sometimes restrict continuous developmental expansion, compelling infilling to occur in less environmentally sensitive zones, which may be fragmented spatially. At the same time, integrating green spaces within urban cores enhances fragmentation by creating a mosaic of built and open spaces. This balancing act between development and sustainability further complicates the spatial morphology of Chinese cities.
The research also utilizes advanced geospatial analytical techniques, combining high-resolution satellite imagery and urban land use datasets to quantify fragmentation patterns dynamically. By measuring changes over time, the authors demonstrate that fragmentation is accelerating in many metropolitan areas, with the rate and intensity remarkably linked to the strategic planning directions adopted by municipal governments. These empirical insights underscore the importance of considering fragmentation metrics as vital indicators for urban sustainability assessment frameworks.
Moreover, the study explores the implications of fragmented built-up areas on urban metabolism—how cities consume resources, produce waste, and function ecologically. Fragmented urban forms tend to increase infrastructure costs and energy use due to scattered service delivery and transportation inefficiencies. The authors caution that without coordinated planning efforts, such spatial fragmentation could undermine the environmental gains of urban densification policies, resulting paradoxically in increased emissions and resource inefficiency.
One of the most compelling aspects of the study is its policy relevance. It calls for a reevaluation of current urban planning paradigms in China, emphasizing integrated and multiscale approaches to manage infilling effectively. The authors advocate for cross-jurisdictional cooperation, innovative land tenure reforms, and incentives to promote contiguous rather than patchy urban growth. Such measures could substantially reduce fragmentation and enhance the livability, functionality, and resilience of Chinese cities.
The transition from dominant edge expansion to increasing infilling marks a pivotal shift in China’s urbanization narrative. This evolution reflects a broader global trend where megacities grapple with land scarcity, sustainability imperatives, and socio-economic complexities. By unpacking the driving forces behind built-up area fragmentation, the research by Hu and colleagues equips urban planners, policymakers, and scholars with essential knowledge to navigate this challenging terrain.
Ultimately, understanding and managing urban fragmentation is critical not only for China but also for cities worldwide confronting rapid transformation in the 21st century. As urban cores become denser and the spatial logic of growth reshapes, strategies must balance development needs with sustainability and social equity imperatives to foster urban environments that are coherent, functional, and adaptable.
This seminal work invites ongoing investigation into the socio-spatial interactions shaping modern urban forms and underscores the imperative of interdisciplinary efforts in urban sustainability research. By integrating technical geospatial analyses with socio-political insights, it sets a new benchmark for studying how cities evolve in response to multifaceted pressures and opportunities.
Subject of Research: Urban built-up area fragmentation and spatial growth patterns in Chinese cities.
Article Title: From dominant edge expansion to increasing infilling: the driving forces behind built-up area fragmentation in Chinese cities.
Article References:
Hu, Y., Hu, T., Xue, F. et al. From dominant edge expansion to increasing infilling: the driving forces behind built-up area fragmentation in Chinese cities. npj Urban Sustain (2026). https://doi.org/10.1038/s42949-026-00346-9
Image Credits: AI Generated
