Assessing the impacts of urban functional form on anthropogenic carbon emissions: A case study of 31 major cities in China

Urban form, which refers to the land use patterns and the structure of transport network within a city, indirectly influences carbon dioxide emissions in cities by impacting fossil fuel consumption in the transportation and residential sectors. Previous studies on the relationships between urban form and carbon emissions have mainly focused on general analysis at city level, usually considering urban built-up areas as homogenous units, while ignoring the spatial heterogeneity of functions within urban built-up areas. To fill the gap, this study aims to examine the impact of urban functional form on carbon emissions in 31 major cities in China by introducing urban functional zones data to capture the spatial heterogeneity of functions within cities. Firstly, ODIAC (Open-source Data Inventory for Anthropogenic Carbon dioxide) was preprocessed to obtain gridded carbon dioxide emission data as dependent variables. Secondly, a comprehensive indicator system was established to quantify the functional form of a city in terms of both land use patterns and transport networks structure as independent variables. Thirdly, a scale sensitivity analysis was then conducted to determine the optimal scale for analyzing the impacts. Finally, lasso regression was utilized to investigate the impact of urban functional form on carbon emissions. Experimental results indicate that 1) the grid size of 6 km is the optimal scale for studying the relationships between urban functional form and carbon emissions; 2) the topology of road networks is more important than its size for influencing carbon emissions; 3) specific relationships between land use patterns and carbon emissions has been revealed, highlighting the importance of considering functional heterogeneity when studying the relationship between urban form and carbon emissions, while simultaneously providing significant guidance for the construction of low-carbon cities. These findings not only provide an important reference for future research (e.g., optimal scale), but also further highlight the theoretical and practical significance of urban functional form adjustment in low-carbon and sustainable urban development. The study offers solid theoretical basis for urban planning, construction and management, demonstrating that urban greenhouse gas emissions can be effectively reduced by optimizing urban form planning, and provides reliable decision support for the development of specific optimization schemes.