School of Economics, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China.
School of Business, Huzhou University, Huzhou, Zhejiang, China.
Environ Sci Pollut Res Int. 2021 Mar;28(11):13404-13424. doi: 10.1007/s11356-020-10669-4. Epub 2020 Nov 12.
The rapid urbanization growth has not only improved the living standards of people but also raised concerns for environmental sustainability over the globe. In this regard, the issue of excessive urban concentration or over-agglomeration in metropolitan areas is nowadays the prime concern for urban planning and building energy-efficient and eco-friendly infrastructures. In response to rising interest in the dynamic linkage between urban concentration and environment, the current research empirically examines the crucial nexus between urban agglomerations and environmental degradation in top ten urban agglomerated countries in the world from 1960Q1 to 2014Q4. The current research is the pioneer empirical work in the area of urbanization by applying recently developed and innovative methods of quantile-on-quantile (QQ) approach and quantile Granger causality in relatively less explored area of urban agglomeration at the cross-country level. Our mainstream findings indicate that urban agglomeration has a strong positive effect on CO emissions in most of our sample countries, and this effect is more pronounced in higher quantiles of respective variables. These results imply that excessive levels of urban concentration in big cities cause environmental degradation, which could be attributed to extreme population density, overcrowding, traffic congestion and extensive demand for energy consumption. However, some countries such as Israel, Paraguay and Columbia exhibit overall declining and negative trends about the relationship between urban agglomerations and CO emissions. Moreover, quantile Granger causality results confirm the previous findings of QQ regression and verify the existence of bidirectional causal nexus between urban agglomerations and CO emissions in the majority of the lower, middle and upper quantiles in our selected top ten countries except for Kuwait. However, the unidirectional causal relationship also exists for several countries for extreme lower, middle and extremely higher quantiles. Our findings extend the previous work on agglomeration-environment nexus by determining the asymmetric magnitude of linkage between these two variables demanding cautious and individual-focused policies for urban planning and environmental sustainability.
快速的城市化增长不仅提高了人们的生活水平，也引起了全球对环境可持续性的关注。在这方面，大都市地区过度的城市集中或过度集聚问题，如今是城市规划和建设节能、环保基础设施的首要关注点。为了应对人们对城市集中化与环境之间动态联系日益增长的兴趣，本研究从 1960 年第一季度到 2014 年第四季度，对世界十大城市群国家的城市集聚与环境退化之间的关键关系进行了实证检验。本研究是在城市化领域的开创性实证工作，应用了最近开发的创新方法——分位数-分位数（QQ）方法和分位数格兰杰因果检验，研究了在相对较少探索的城市群跨国层面的问题。我们的主流发现表明，在我们的大多数样本国家中，城市群对 CO 排放有很强的正向影响，而且这种影响在变量的较高分位数上更为明显。这些结果表明，大城市过度的城市集中化会导致环境恶化，这可能归因于极端的人口密度、过度拥挤、交通拥堵和对能源消耗的广泛需求。然而，一些国家，如以色列、巴拉圭和哥伦比亚，整体上表现出城市群与 CO 排放之间的关系呈下降和负向趋势。此外，分位数格兰杰因果关系的结果证实了 QQ 回归的先前发现，并验证了在我们选择的十大国家中，除科威特外，大部分较低、中、上分位数的城市群与 CO 排放之间存在双向因果关系。然而，对于几个国家的极端低、中、极高分位数，也存在单向因果关系。我们的研究结果通过确定这两个变量之间联系的不对称程度，扩展了关于集聚-环境关系的先前工作，这要求在城市规划和环境可持续性方面采取谨慎和注重个体的政策。
