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Chinese urbanization 2050: SD modeling and process simulation

Science China Press

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Chinese urbanization has profoundly contributed to the whole country's economic growth, social advancement and life improvement. Parallel to this process, however, China has confronted a series of problems, such as loss of agricultural land, reduction in biodiversity, unaffordable urban housing, problematic transportation, uneven regional economic development, etc. Despite of these difficulties, still China has to continue its way towards urbanization but in a new mode. That is, Chinese New Urbanization mode which has already been set as the central task for China to completely recognize a well-developed society by 2020. Nevertheless, two critical yet not solved questions decisively influencing China's urbanization agenda still persist: What is the highest stable urbanization level that China can reach? When can China complete its urbanization? In fact, these two questions have already been widely studied. But due to each study's inherent limitation, there are prominent differences or even contradictions among these existing research conclusions, which resulted in the policy makers' struggling to decide which conclusion should be set as the foundation for formulating China's New Urbanization plans. To tackle this challenge, a Chinese research team has recently proposed a multi-dimensional system dynamic (SD) simulation model of Chinese urbanization from the perspective of complexity. This model enables users to examine the complex process of Chinese urbanization in a dynamic perspective. Through robust model verification and validation against historical data, this model, compared with the existing ones proposed by other scholars, has much higher reliability, credibility and practicality. Through this model the policy makers can generate more scientific policies and development schemes for China's New Urbanization towards 2050.

A paper explaining the details of the model and its application has been published in 2017?6?issue of SCIENCE CHINA Earth Sciences. Its title is "Chinese urbanization 2050: SD modeling and process simulation", with Prof. Gu Chaolin from the School of Architecture, Tsinghua University as the first author and corresponding author, and the principle investigator in this research project. The research team successfully applied the SD modelling approach to understand Chinese urbanization process. It not only gives details of China's urbanization mechanism constrained by environmental sustainability in a comprehensive view but also its representation in full mathematic expression. In addition, the research put forward an SD modelling framework customized to China's New Urbanization (Figure 1) which specifies the model's mathematic logic, the structure of the subsystems for SD modelling and the modelling techniques for simulating the interactions among these subsystems. With robust model validation, the paper finally presents us with the ultimate urbanization levels China can achieve in multiple scenarios.

It is hold by the research team that there are three key challenges in parallel with the application of SD modelling to Chinese urbanization process. The first one is to quantify the underlying urbanization mechanism with high accuracy while the second is to justify the model's validity with convincing evidence in the context of China. And the last one is to insure the flexibility of the model's applicability so that it can support urbanization policy making with high scientificity. In the modelling process, the causal-loop diagrams of the sub-systems representing each dimensions of the mechanism are assembled into stock and flow diagrams, including main factors and subsystems such as industries, population, cities and towns, education, etc. (Figure 1). Then, supported by packages including DYNAMO, iThink, Vensim® and Powersim®, the theorized Chinese urbanization process is modeled using SD methodology. The conformity of the model is validated against the historical data from 1998 to 2013 while the model's stability and degree of confidence are justified by differential equation approach. To increase the model's applicability, two critical elements including GDP growth rate and family planning policy fundamentally concerned in China's New Normal era are considered. With combinations of different values of these two parameters, the ultimate urbanization level and the year in which it can be achieved in a series of scenarios are simulated and explained.

The research is funded by the key project of the National Natural Science Foundation of China (Grant No. 41590844) and the independent research program of Tsinghai University (Grant No. 2015THZ01). The proposed framework of Chinese urbanization process is expected to quantitatively analyze the underlying mechanism of Chinese urbanization and its ultimate urbanization level with systematic view and scientific foundation. With no doubt the generated conclusions will provide all the tiers of governments in China reliable evidence for policy making and policy implementation throughout the process of China's New Urbanization.

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For more information, please refer to

GU ChaoLin, GUAN WeiHua, LIU HeLin. Chinese urbanization 2050: SD modeling and process simulation. SCIENCE CHINA Earth Sciences, 60(6): 1067-1082, doi: 10.1007/s11430-016-9022-2

https://link.springer.com/article/10.1007/s11430-016-9022-2

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