The impacts of urban forms on CO2 emissions in Yangtze River Delta urban agglomeration in China

CO2 emission reduction is bound up with sustainable development, and cities increasingly become the main battlefields for combating CO2 emission-related issues. It is argued that urban form is strongly interconnected with CO2 emission reduction utilizing energy consumption, transportation behaviour and land utilization. As elements of urban form, urban size and density are considered closely related to CO2 emission performance. There have been constant discussions about the optimal urban size and density as well as their relations with CO2 emission, but no consensus has been reached. Moreover, with the increasingly important role of urban agglomeration in urbanization, the pros and cons of urban agglomeration in CO2 emission reduction are worth understanding. This study aims to make a contribution to the existing body of knowledge of the relationships between urban form and CO2 emission, and also aims to find out whether urban agglomeration can play a positive role in improving the efficiency of CO2 emission. The results of this study can add fresh blood to strategies in combating climate change, give insight on how urban form strategies can be used to reduce emission for urban sustainable development, and help urban policy-makers move forward in making right decisions in creating urban forms to reduce CO2 emissions. The secondary analysis and the policy analysis methods are both used in this study. In the method of the secondary analysis, temporal analysis and spatial analysis are applied to the analysis of the temporal and spatial changes of the urban form CO2 emissions, while regression analysis is conducted to figure out the relationship between urban form and CO2 emissions both by non-spatial model and spatial model. Additionally, the policies related to CO2 emissions mitigation and urban agglomeration development will be analysed in policy analysis to investigate the aspects for further improvement. The research identified several findings, mainly including: (1) There is U-shape relation between population size and CO2 emissions, and the ideal population size of cities for lowest CO2 emissions in Yangtze River Delta (YRD) urban agglomeration is 2.716 million. (2) There is a negative relationship between CO2 emissions and density, which shows that when population density increases 1%, the CO2 emissions will decrease 0.426% approximately. (3) urban agglomeration played a positive role in CO2 emissions mitigation, by controlling the total CO2 emissions, improving the emissions efficiency as well as eliminating the spatial agglomeration of CO2 emissions. These findings confirm the significantly important roles of population size and density as elements of urban form for CO2 emissions reduction in urban agglomeration areas and provide policymakers with the scientific basis for future spatial plan and sustainable development in YRD urban agglomeration.