长江三角洲一体化区域扩容对城市碳排放强度的影响评估与机制

Impact of regional integration area enlargement on urban carbon emission intensity and mechanism:An empirical study based on the Yangtze River Delta

在落实“双碳”目标、推进城市群战略背景下,长江三角洲一体化区域扩容,对城市碳排放强度有何影响?本文将“长江三角洲城市经济协调会”扩容作为一项准自然实验,基于双重差分模型,多角度探讨一体化区域扩容对城市碳排放强度的影响,并采用中介模型、调节模型分析影响机制。结果表明:(1)一体化区域扩容能够显著降低城市碳排放强度,且考虑平行趋势、内生性、外部冲击、差异化碳排放估算方法等的稳健性检验依然显著。(2)一体化区域扩容对城市碳排放强度的影响呈现多重异质性,如时间上城市加入协调会时间越长、对碳排放强度下降促进作用越大,区域上加入协调会对苏皖城市影响呈显著负效应、浙江城市影响呈不显著正效应,城市类型上加入协调会对高等级城市碳排放强度下降促进作用强于一般城市。(3)加入协调会带来的市场一体化深化、产业升级加快、绿色创新技术提升、协同治理深化等,是一体化区域扩容驱动城市碳排放强度下降的重要机制,且城市市场化程度提升、产业高级化推进,能够放大一体化区域扩容对城市碳排放强度下降的促进作用。研究结论验证了通过一体化推动城市群绿色发展的可行性,但也表明推动一体化城市协同发展的政策制定、实施应“因地制宜”。

In the process of achieving peak carbon emissions by 2030 and the carbon neutrality targets by 2060 in China, the Yangtze River Delta urban agglomeration is taking the lead in realizing low-carbon development, which is of great practical significance for supporting and leading the high-quality development of China. In the context of the further promotion of urban agglomeration development strategy, will the gradual expansion of the integrated region of the Yangtze River Delta, which has reduced administrative barriers and optimized the allocation of factors, have any impact on the urban carbon emission intensity? Based on the prefecture level panel data of the Yangtze River Delta, this study regarded the expansion of the Yangtze River Delta Urban Economic Coordination Committee as a quasi-natural experiment and used the difference-in-differences model to estimate the impacts of regional integration area enlargement on urban carbon emission intensity from multiple perspectives. Furthermore, we identified the mechanisms by using the mediation effect model and moderation effect model. The results show that regional integration area enlargement significantly reduced urban carbon emission intensity, and after considering a series of robustness tests such as parallel trends, endogeneity, external shocks, and differentiated carbon emission measurement method the results were still significant. Further research revealed that there were multiple heterogeneous impacts of regional integration area enlargement on urban carbon emission intensity. For example, the longer the integration into the urban agglomeration, the more significant the reduction of carbon emission intensity;Regionally, there were significant negative impacts of cities in Jiangsu and Anhui Provinces, and a non-significant positive impact of cities in Zhejiang Province;Compared to low hierarchical level cities, regional integration area enlargement had a greater impact on the carbon emission intensity reduction of cities of high hierarchical level. Mechanism verification showed that regional integration area enlargement reduced urban carbon emission intensity through the strengthening of market integration, the upgrading of the industrial structure, the promotion of green innovation technology, and the deepening of urban collaborative governance. In addition, the promotion of marketization degree and industrial structure upgrading could amplify the positive impact of the regional integration area enlargement on the reduction of urban carbon emission intensity. This study verified the feasibility of promoting green development of urban agglomeration through regional integration, and from the perspective of better achieving the goal of high-quality integration in the Yangtze River Delta, the formulation and implementation of relevant policies aimed at promoting coordinated development should adapt to local conditions.