经济学院知识库

       随着人口的快速流动与迁移，我国人口在空间上呈现明显的集聚态势。人口作为信息、技术和资本的载体，在区域内集聚能够改变城市的经济结构、产业布局和资源状况，对经济和环境产生重要影响。其中，碳排放是近年来讨论的热点话题，实现“双碳”目标是贯彻新发展理念、构建新发展格局、推动高质量发展的内在要求，具有紧迫性和艰巨性。在此背景下，深入探究我国城市层面人口集聚对碳排放的影响及其传导路径，并分析不同特征城市间的异质性，对我国低碳城市建设与节能减排具有重要意义。
       本文以2006-2021年中国254个地级及以上城市为研究对象，首先，依据已有研究成果与理论基础，构建人口集聚对城市碳排放影响的理论机制并提出研究假设。其次，考虑多方面因素选择恰当方法测度人口集聚和城市碳排放，并从时序变化、区域差异、空间关联三个角度对人口集聚和城市碳排放进行现状分析。最后，以STIRPAT模型作为基准回归模型，在通过多重模型检验的基础上，选用空间杜宾模型等计量经济学方法实证分析人口集聚对城市碳排放的非线性影响及其传导路径；并按照城市的区位、行政区划等级、规模大小、发展进程的不同将全样本城市进行划分，进一步探讨不同特征城市人口集聚对城市碳排放影响的异质性。研究结果显示：（1）人口集聚显著影响城市碳排放，并且呈“U”型非线性特征。（2）人口集聚会通过“人口集聚—产业结构升级—城市碳排放”、“人口集聚—基础设施建设—城市碳排放”两条路径影响城市碳排放。（3）不同特征城市人口集聚对碳排放的影响具有明显异质性。东部、中部地区人口集聚对城市碳排放均具有明显的抑制作用，而西部和东北地区人口集聚对城市碳排放的影响具有“U”型的非线性特征；直辖市和副省级市人口集聚对城市碳排放具有抑制作用，而地级市人口集聚对城市碳排放的抑制作用相对较差；大城市人口集聚对城市碳排放具有显著抑制作用，但超大特大城市人口集聚对城市碳排放的抑制作用相对较差，中小城市人口集聚对城市碳排放的影响具有“U”型的非线性特征；工业化发展阶段的城市人口集聚对城市碳排放具有抑制作用，而后工业化阶段的城市人口集聚对城市碳排放的抑制作用相对较差。
       基于上述结论，本文从加强相邻区域协同管理、推动以人为本的新型城镇化、加大产业结构升级转型力度、实施符合自身城市特点的人口管理政策等角度提出相关建议，为不同城市更大程度发挥人口集聚正外部性并实现节能减排提供启示和借鉴。
 

       With the rapid flow and migration of the population, China's population presents an obvious gathering trend in space. As the carrier of information, technology and capital, population gathering in a region can change the economic structure, industrial layout and resource status of the city, and have an important impact on the economy and environment. Among them, carbon emission is a hot topic discussed in recent years, and the realization of the goal of "double carbon" is an inherent requirement for implementing the new development concept, building a new development pattern, and promoting high-quality development, which is urgent and arduous. In this context, it is of great significance to explore the impact of population agglomeration on carbon emission and its transmission path, and to explore the heterogeneity of cities with different characteristics, which is of great significance to the construction of low-carbon cities and energy conservation and carbon reduction in China.
     This paper took 254 cities at prefecture level and above in China from 2006 to 2021 as the research object. First of all, based on the existing research results and theoretical basis, the theoretical mechanism of the impact of population agglomeration on urban carbon emissions is constructed and the research hypothesis is proposed. Secondly, considering various factors, we choose appropriate methods to measure population agglomeration and urban carbon emissions, and analyze the spatial-temporal changes of population agglomeration and urban carbon emissions from three perspectives: time series change, regional difference and spatial correlation. Finally, the STIRPAT model is used as the benchmark regression model, and on the basis of passing the multiple model test, the Spatial Durbin Model, mediating effect model and other econometric methods are used to empirically analyze the nonlinear impact of population agglomeration on urban carbon emissions and its transmission path. And according to the location of the city's size and the development process, administrative levels, different cities divided the whole samples, further explore different characteristics of the urban population agglomeration heterogeneity influence on urban carbon emissions. The main conclusions are as follows: (1) Population agglomeration has a significant impact on urban carbon emissions, and it presents a U-shaped nonlinear characteristic. (2) Population agglomeration affects urban carbon emissions by affecting industrial structure upgrading and infrastructure construction. (3) The effects of population agglomeration on carbon emissions in cities with different characteristics have obvious heterogeneity. The population agglomeration in the eastern and central regions has a significant inhibitory effect on urban carbon emissions, while the population agglomeration in the western and northeastern regions has a U-shaped nonlinear effect on urban carbon emissions. The population agglomeration of municipalities directly under the central government and sub-provincial cities has an inhibitory effect on urban carbon emission, while the population agglomeration of prefecture-level cities has a relatively poor inhibitory effect on urban carbon emission. The population agglomeration of large cities has a significant inhibitory effect on urban carbon emissions, but the population agglomeration of megacities has a relatively poor inhibitory effect on urban carbon emissions, and the population agglomeration of small and medium-sized cities has a U-shaped nonlinear characteristic. The population agglomeration in the stage of industrialization has an inhibitory effect on urban carbon emission, while the population agglomeration in the post-industrialization stage has a relatively poor inhibitory effect on urban carbon emission.
     Based on the above conclusions, this paper puts forward relevant suggestions from the perspectives of strengthening the coordinated management of neighboring regions, promoting people-centered new-type urbanization, intensifying the upgrading and transformation of industrial structure, and implementing population management policies in line with their own urban characteristics, so as to provide inspiration and reference for different cities to realize energy conservation and emission reduction.