The integrated development of urban and rural areas refers to the dynamic process of achieving all-round human development through the formation of new regional organizational structure, balanced resource element allocation pattern, complementary urban and rural functional patterns, etc. under the condition of full development of social productive forces, which is caused by system reform, technological progress, demand growth, and cultural innovation and so on. The integrated development of urban and rural areas can effectively solve the problem of insufficient rural development in China, and finally solve the problem of insufficient and unbalanced development in China, so as to achieve high-quality development and common prosperity. The reports of the 19th National Congress of the Communist Party of China called for “the establishment and improvement of systems, mechanisms and policy systems for integrated urban-rural development, and the acceleration of agricultural and rural modernization”, and opened a new starting point for building systems and mechanisms for integrated urban-rural development. On April 15, 2019, Opinions of the CPC Central Committee and the State Council on Establishing and Improving Systems, Mechanisms and Policy Systems for Integrated Urban-rural Development pointed out that “fully consider the different stages of regional urban-rural integration development and rural differences, act in a cautious and appropriate way concerning the timing, the rhythm and step of reform, respect for the grassroots initiative, give full play to the initiative of local governments, implement policies in different categories and in different steps, pilot projects first and work hard for a long time to form a practical and distinctive reform path and a model of integrated urban and rural development”, further pointing out the specific implementation path of establishing and improving systems and mechanisms for integrated urban and rural development. The huge market demand generated by the economic development in the new era and the substantial improvement of rural working and living conditions have greatly enhanced the connectivity between urban and rural areas, creating huge space for promoting the integrated development of urban and rural areas and creating new conditions for the establishment of institutions and mechanisms for the integrated development of urban and rural areas. To establish and improve effective systems and mechanisms and promote the healthy development of urban-rural integration, we must comprehensively grasp the development of urban-rural integration. Based on this, this paper attempts to make a comprehensive introduction to the research on urban-rural integrated development by sorting out, analyzing and summarizing the relevant important research results at home and abroad, so as to provide a theoretical basis for the establishment and improvement of the urban-rural integrated development system and mechanism in China.
2. The Academic History and Research Trends of Related Research Abroad
The theory of urban-rural integrated development originated in the 16th century, when the British utopian socialist Thomas Moore first proposed the idea of “urban-rural integration” in his book Utopia, which was the original germination of the idea of urban-rural integrated development. Later, Marx and Engels, on the basis of critically absorbing the reasonable views of utopian socialist “urban-rural integration” thought, creatively analyzed the development law of urban-rural relations from the perspective of the development of productive forces and social division of labor, believing that the integrated development of urban and rural areas is the inevitable result of the highly developed productive forces and the development of urban-rural relations can be divided into three stages: chaos, disjunctive opposition, and integration. This theory profoundly reveals the essence and law of urban and rural social development and forms a relatively mature thought of urban and rural integrated development. Western scholars after Marx and Engels have made valuable discussions on the relationship between urban and rural areas. Lewis (1954), Perou (1955), Hirschman (1958), Friedman (1966), Jorgensen (1971) et al. studied the interaction and its effects between economically developed and underdeveloped regions in the stage of “disjunctive opposition”. Lewis (1954), Perou (1955), Hirschman (1958), Friedman (1966), et al., advocated the “urban bias” of industrial and urban dominance, while Jorgensen (1971) supported the “rural-centrism” view that agricultural surplus products played an important role in economic growth. The “urban bias” theory and the “rural-centrism” theory give a good explanation and suggestion for the development of rural-urban relationship in the stage of “disjunctive opposition”. Howard (1898), Mumford (1961), McGee (1985), et al., discussed the planning concept and motive force of development of “integrated development” stage. Howard (1898) and Mumford (1961) emphasized that rural and urban improvement should be treated as a unified problem, and the basic idea is still useful today. Maggie (1985) proposed to analyze the driving force of urban-rural integration development from two aspects: revolution of transportation and communication means and wave of international division of labor. These studies are the enrichment and perfection of Marx and Engels’ thoughts on urban-rural relations and provide beneficial reference for the urban-rural development in China. Under the guidance of Marx, Engels and other theories of urban-rural relations, we should creatively explore the new thoughts and practices of urban-rural integration with Chinese characteristics in the new era to study the integrated development of urban and rural areas in China.
3. Domestic Academic History and Research Trends of Related Research
Since the end of 1980s, the imbalance between urban and rural development has been widely concerned. The policy of urban and rural development has experienced the evolution of urban and rural overall development → city and countryside integration → and urban-rural integration. Entering the new era, comrade Jinping Xi pays more attention to urban and rural integration development, thinking that “In the process of modernization, how to deal with the relationship between workers and peasants, urban and rural areas, to a certain extent, determines the success of modernization”, “We will take the road of integrated urban-rural development, give impetus to reform, and accelerate the establishment and improvement of systems, mechanisms and policy systems for integrated urban-rural development”.
Chinese scholars have conducted in-depth research on the integrated development of urban and rural areas from both theoretical and practical aspects. In theory, Xianjiang Liu (2013) , Qiaofei Wu (2014) , Hui Zhang (2018), Diansheng Guo (2019), Cailing Xu (2019), Jun Jiang (2019) and others summarized and sorted out Marx’s thoughts on urban-rural integration, so as to provide references for contemporary urban-rural integration development. Yansui Liu (2018) , Renwei He (2018), Chunfang Liu (2018), Zhiheng Yang (2019), Chengwu Jin (2019)  et al. studied the theoretical origin, theoretical connotation and integration mechanism of urban-rural integrated development from different dimensions, which provided a theoretical basis for the research on urban-rural integrated development model and mechanism. In practice, Bogeng Chen (2013) , Kai Zhou (2014), Yuanji Huang (2019) , Jiming Cai (2019) , Deqi Zhao (2019), Jun Jiang (2019) and others studied the calculation of urban-rural integration degree, existing problems, dynamic mechanism, influencing factors, realization path and development experience from the national perspective. From a regional perspective, Shujian Zheng (2014), Leilei Guo (2019), Wei Xing (2019)  conducted an empirical study on the urban-rural integration development of villages in the pearl river delta region, the western region and the poor region, and finally found that planning, environment, industry, spatial structure and infrastructure play an important role in urban-rural integration. Bingqing Chen (2019) , Qianhu Chen (2019) et al. conducted empirical research on the spatial integration of urban and rural areas in Jiangsu province and the development of small towns in Zhejiang province from the provincial level, concluding that the rapid improvement of social and economic development level, the rapid development of township enterprises, the continuous improvement of transportation infrastructure, the rapid construction of development zones and new urban areas and the establishment of urban-rural integration system and mechanism can effectively promote urban-rural integration. Starting from the municipal perspective, Huaiyou Shao (2007), Jinghe Liu (2009), the research group of Wuhan institute of development strategy (2012), Wang Zhang (2013), Yuxin Feng (2014), Wei Fu (2018), etc. took Fuzhou city of Fujian province, Xuchang city of Henan province, Wuhan city of Hubei province, Meishan city of Sichuan province, Wuwei city of Gansu province and L city of Zhejiang province as the research objects, focusing on the analysis of relevant factors that should be paid attention to in planning, like: the concept of sustainable development, the endogenous driving force of rural society, the development trend of urban-rural integration area, historical and cultural resources, etc. From the perspective of district and county, Longsheng Yu (2011), Xiaoyun Li (2012), Hongling Ye (2018) et al., took Panyu district and Huadu district of Guangzhou, and Gaoling district of Xi’an city as research objects, focusing on the landscape change and land system reform under the integration of urban and rural space.
There are relatively few research documents on the integrated development of urban and rural areas in the old revolutionary base areas, except some case studies on Jurong city of Jiangsu province (Changsheng Yin, 2011), Lizhou district of Guangyuan city (Jian Liu, 2014) and Zhashui county of Shaanxi province (Haichun Zhao, 2015).
To sum up, domestic and foreign scholars have studied the integrated development of urban and rural areas from different perspectives and achieved fruitful research results, which are worthy of learning and reference, but there is also some room for improvement. First, the evaluation system of integrated urban and rural development needs to be further improved. The existing evaluation system of rural-urban integration development focuses on the evaluation of the core elements of rural-urban integration, lacking consideration on the preconditions and results of the integrated development of urban and rural areas. Second, the specific implementation plans of ecology and culture in industrial development and spatial planning need to be strengthened. Although the status and role of ecology and culture in the integrated development of urban and rural areas have been paid more and more attention in recent years, the relevant research on how to embody ecology and culture in industrial development and spatial planning is still insufficient. Third, the model and mechanism of integrated urban-rural development in old revolutionary base areas need to be strengthened. The existing researches mainly focus on the national perspective and the developed areas in the central and eastern regions, and lack a comprehensive perspective on the urban-rural integrated development model and mechanism in the old revolutionary base areas.
To establish and improve effective systems and mechanisms for the integrated development of urban and rural areas, we should, on the basis of the existing research results, follow the principle of making the best of our strengths and avoiding the worst of our weaknesses and the principle of adapting measures to local conditions so as to promote the healthy development of the integrated development of urban and rural areas in China.
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