An integrated approach for examining urban fragmentation in metropolitan areas: Implications for sustainable urban planning

Urban fragmentation is generally regarded as a strong urban structural polarisation that is closely related to sustainability, yet a comprehensive understanding of the management of different fragmentation scenarios and their causes is still lacking. The Wuhan metropolitan area, as a rapidly urbanising region, shows clear evidence of different forms of urban fragmentation due to rapid urbanisation and spatial differentiation in pedestrian network structure, neighbourhood residential pattern and land use structure. In this study, an integrated framework for examining the fragmentation of dynamic and complex metropolitan areas, is proposed. The results indicate that the 49 highly fragmented sub-districts are distributed with large gated communities, industrial parks, green spaces and rivers/lakes. The fragmentation forms of the Wuhan metropolitan area include morphological, connectional and functional (variety and conflict) fragmentation, which constitute six scenarios. The geographical detector model manifests that urban fragmentation is the result of natural, socio-economic and construction factors. The increase in spatial debris driven by housing prices (q = 0.334), gross domestic product (q = 0.282), population density (q = 0.359), constructive index (q = 0.292) and road density (q = 0.314) has dramatically affected spatial organisation co-evolution. Additionally, there are synergistic enhancement effects between each pair of driving factors, i.e., bivariate or nonlinear interaction strengthens the impact of each other factor on the index of urban fragmentation. The strongest bivariate interaction is between housing prices and constructive index, with a value of 0.503. The largest nonlinear interaction is between constructive index and industrial index, with a value of 0.487. These interactions all further exacerbate urban fragmentation. These findings not only contribute to an integrated methodological framework, but also provide scientific implications for the purpose of sustainable urban development and cleaner production planning.