外部性视角下中国城市网络演化及其环境效应研究

在全球化、快速城市化和新技术革命的背景下,要素流与网络关系构成的“流空间”愈发重要,城市网络结构不断受到冲击与重塑,人地关系矛盾日益凸显,区域空间组织模式及其环境效应已成为环境经济地理学研究的重要议题。本文利用腾讯位置大数据,构建了2015—2018年288个地级以上城市之间的人口迁徙网络,采用社会网络分析和面板空间计量模型,对中国城市网络演化格局及其环境效应进行实证分析。结论如下：① 中国城市网络联系强度高的城市主要分布在“胡焕庸线”东侧的京津冀、长三角、珠三角和成渝城市群组成的菱形结构;城市网络密度和关联性逐渐增强,度数和中介中心性呈现多中心和分散化的发展趋势。② 中国城市空气质量总体有所好转,空间上呈现显著的集聚特征;88.89%的城市空气质量指数（AQI）下降,PM_2.5、PM₁₀、SO₂、CO和NO₂年均浓度有所下降,而O₃年均浓度有所上升。③ 中国城市网络对环境质量的影响主要来源于城市网络外部性所带来的空间溢出效应;城市网络中节点权力地位和影响力的增强,提高了借用规模和借用技术,从而促进环境质量提升。④ 度数中心性提升了东部、中部和东北地区的环境质量,减少了PM_2.5、PM₁₀、SO₂和O₃的年均浓度,增加了CO的年均浓度;而中介中心性则提高了西部地区的环境质量,降低了NO₂的年均浓度。

The evolution of China's city network and its environmental effects from the perspective of externalities

Under the background of globalization, rapid urbanization and new technological revolution, the "flow space" composed of factor flow and network relationship was becoming more and more important, the city network structure was constantly impacted and reshaped, the contradiction of man-land relations was becoming increasingly prominent, the regional spatial organization patterns and its environmental effect have become an important topic of environmental economic geography research. In this paper, we used Tencent location big data to establish population migration network among 288 China's cities above prefecture level from 2015 to 2018, and employed social network analysis and panel spatial econometric model to empirically analyze the evolution patterns of city network and its environmental effects in China. The results show that: (1) Cities with high connection strength in China's city network are mainly distributed in the rhombus structure consisting of the Beijing-Tianjin-Hebei, Yangtze River Delta, Pearl River Delta, and Chengdu-Chongqing urban agglomerations in the region east of the Hu Huanyong Line. China's city network density and relevance were gradually increasing, and degree centrality and betweenness centrality presented a trend of multi-center and decentralization. (2) On the whole, China's urban air quality has improved, showing significant agglomeration characteristics in space. Ambient Air Quality Index (AQI) decreased in 256 cities (88.89% of the country's total number). The annual average concentrations of PM_2.5, PM₁₀, SO₂, CO, and NO₂ declined while that of O₃ increased. (3) The impact of China's city network on environmental quality were mainly due to the spatial spillover effect brought by the externality of the city network. The enhancement of the city's degree centrality could increase the ability of the borrowing size and borrowing technology to gain development advantages, thereby promoting the improvement of environmental quality. (4) The upgrade of city's degree centrality has improved the environmental quality of the eastern, central and northeastern regions, reducing the annual average concentration of PM_2.5, PM₁₀, SO₂ and O₃, but that of CO was increasing, while the enhancement of city's betweenness centrality has improved the environmental quality of the western region and significantly reduced the annual average concentration of NO₂.