“…Last but absolutely not least, the expansion of urban population leads to more diverse and concentrated production and consumption activities which contributes significantly to the environmental degradation by emitting a larger amount of CO 2 gas (Al-Mulali, Ozturk, & Lean, 2015;Liddle, 2014;Wang et al, 2016;Wang, Zhang, Kubota, Zhu, & Lu, 2015;Wu, Y., Shen, Zhang, Skitmore, & Lu, 2016;Zhang, Liu, Zhang, & Tan, 2014;Zhang, Liu, Qin, & Tan, 2017). For example, Wang et al (2015) have confirmed the urbanisation-emission EKC hypothesis which means the inverted U-shaped curve of this relationship in the OECD (Organization for Economic Co-operation and Development) countries.…”