As more and more rural people choose to enter the city, many cities around the world are expanding rapidly. 2018 Revision of World Urbanization Prospects of United Nations [1
] shows that the urban area has gathered more than half of the world’s population and is also the core area for future population growth. It is estimated that by 2050, about 70% of the world’s population will live in cities. Since the reform and opening up, China’s urbanization process has been accelerating, and the urbanization rate has increased from 17.90% in 1978 to 58.52% in 2017 [2
]. The urban agglomeration is the product of the industrialization and urbanization transformation to the advanced stage [3
]. Since the beginning of the 21st century, the UA has become a new regional unit for countries around the world to participate in global competition and international division of labor, and also the main body of China’s new urbanization process. China’s rapid urbanization and industrialization have led to severe pressures on resources and ecological environment, resulting in urban agglomeration diseases such as environmental pollution, traffic congestion, and degraded energy shortages in ecosystems. In order to completely resolve the contradiction between economic construction and ecological, social, and cultural construction, the central government decided to implement party and state institutional reforms, and merge, classify, and reorganize the Party Central Committee and the State Council departments with similar responsibilities to improve the efficiency of functional allocation. The main function of the newly established MNR is to uniformly exercise the duties of all-natural resource asset owners on behalf of the state and to uniformly exercise all land space use control and ecological protection and restoration duties. The current core task of MNR is to establish a national territorial spatial planning system (NTSPS), and to focus on promoting spatial governance and spatial structure optimization in urban agglomerations by judging the quality and potential of land space development. However, how to scientifically determine the intensity and potential of land spatial development is related to the quality and implementation effect of NTSPS. It is a major scientific problem that needs to be solved.
As early as 2006, the Chinese government proposed urban agglomerations as a key strategy to promote urbanization, in line with China’s attempts to enhance resource carrying capacity and environmental preservation. After 10 years of rapid development, urban agglomerations have become the main body of ‘new urbanization’ (people-oriented urbanization) in China [4
]. To further optimize growth and urbanization, the 13th Five-Year Plan, released in March 2016, clearly highlighted the need for the reasonable and strategic distribution of cities to achieve harmonious development.
China plans to build 19 urban agglomerations, including 5 national-level urban agglomerations (Yangtze river delta UA, Pearl River Delta UA, Beijing–Tianjin–Hebei UA, the middle reaches of the Yangtze River UA, Chengdu-Chongqing UA), 8 regional-level urban agglomerations (Shandong Peninsula UA, Harbin-Changchun UA, Mid-southern Liaoning UA, West Taiwan Strait UA, Guanzhong UA, the Central Henan UA, Beibu Gulf UA), and 6 local-level urban agglomerations (Hubao Eyu UA, Jinzhong UA, Along the Yellow River in Ningxia UA, Lanzhou-Xining UA, Central Yunnan UA and Central Guizhou UA). Meanwhile, 19 urban agglomerations were created to support urbanization, and the development and construction of urban agglomerations have become one of the most significant strategies for national development. The national-level urban agglomerations have matured and limited space for improvement. SPUA is the fourth largest urban agglomeration in coastal area of China and located on the banks of the Yellow Sea and the Bohai Sea [5
]. As the primary area of regional economic development in China, SPUA was listed as the frontier of open competition in the report of the 19th National Congress. SPUA is still in its early stages of development. Despite the strong development momentum in Qingdao, Jinan, and other node cities, there are widespread phenomena such as disordered and inefficient land use, unbalanced potential of development, and pollution of ecological environment. As the link between the Yangtze River Delta urban agglomeration and the Beijing–Tianjin–Hebei urban agglomeration, the development of SPUA is related to the overall rise of the entire eastern coastal region of China. It is imperative to establish a scientific and healthy development path to ensure the coordinated development of the urban agglomeration. At the same time, it could provide experience for the healthy development of other UAs in China.
Since the reform and opening up in 1978, urbanization and industrialization in China have sped up, and the development and utilization patterns of the nation’s lands have experienced great changes. These changes are mainly embodied by the strengthening of land development intensity (LDI) [6
], the rapid expansion of construction land, and the continuous decrease in natural eco-spaces [9
]. The strengthening of LDI has led to conflicts between economic and social development and environmental protection, resulting in severe challenges for sustainable development [14
]. In recent years, as global environmental problems have intensified, countries around the world have made a target of green, healthy, and sustainable development to adjust their development models. China has also introduced a new urbanization development strategy, and the core idea behind the strategy is the green, healthy, and sustainable development of the nation’s land resources. The path for development has thus become a hot topic, and how to scientifically regulate and control the LDI has become the essential problem for realizing the development goals [15
The land development intensity evaluation (LDIE) is conducive to optimizing land development and utilization. This complicated and systematic method has attracted attention from many scholars. Existing research is mainly focused on the current development scale, the identification of factors driving development [16
], temporal-spatial differentiation and patterns of urban land expansion [17
], the productivity and efficiency of construction land use [21
], and the evaluation of development potential [23
]. Three above conditions (i.e., scale, efficiency, and potential) should be simultaneously taken into consideration to achieve the goal of sustainable development. Development scale is described as the extent to which urban agglomeration land space is exploited, which means the mass of land development. Utilization efficiency reflects the efficiency of the developed urban agglomeration space, and potential reflects the area that could be further used for construction purposes. Although these three elements should be regarded as a unified whole, little research has considered all three elements. In a study on space exploitation and the division of a drainage basin, Wang (2012) established a three-dimensional distinguishing matrix model deals with the relationship of the spatial development constraint indexes, space development intensity indexes, and space development guidance indexes [24
]. This method gives us a good idea, and we attempt to extend its research from the basin to the urban agglomeration in this paper.
The evaluation of technology and methodology is the core of research in this area. In 1969, the American landscape architect McHarg proposed an evaluation method for the ecological suitability of land use from the perspective of superposition [25
]. This evaluation method has become the basis for initial studies on modern land use and development intensity. In the past 40 years, LDIE has gradually become a significant method in urban and regional planning along with ecological and environmental planning. The main methods used can be categorized into two types [26
]: (1) the element superposition method, which is rooted in the hand-drawn overlay techniques created by McHarg, Steinitz, and others [29
]; and (2) the multi-criteria evaluation method based on GIS (MCE-GIS), which is applied in this study [30
]. MCE-GIS includes methods such as interval multi-objective linear programming model [17
], technique for order preference by similarity to an ideal solution (TOPSIS) [33
], concordance analysis [34
], analytic hierarchy process [35
], fuzzy evaluation method [36
], and a new identification method of priority landscapes and spatial conflicts with new investment area [37
]. The second method is artificial intelligence, for which the main applications include fuzzy mathematics methods [38
], artificial neural networks [41
], matter-element models [42
], cellular automata [43
], and genetic algorithms [44
]. In addition to the two types of methods mentioned above, an ecological niche-based method for assessing the suitability of land [45
] along with a comprehensive evaluation of land based on public participation [46
] (Shearera & Xiang, 2003) have appeared in recent years. Although the assignment of weights to index elements involves uncertainty [26
], weighting methods are still the most widely used within LDIE research due to their simplicity and compatibility with GIS [47
]. Landscape capacity assessment method become more and more popular in land spatial planning intensity. The base for assessing the possibility of new investment areas is an evaluation of landscape features which influence on possibility to hide new building area in landscape. This method is useful for planning development of suburban areas, especially those parts with high-value landscape [48
]. However, based on the relationships among mass, efficiency, and potential, regulating and controlling the path and object of LDIE is regarded as a three-dimensional supporting relationship, it cannot be simply expressed by a weighted stack. So, we learn from the three-dimensional distinguishing matrix model to deal with the relationship of scale, efficiency, and potential in LDIE.
Although LDIE has been frequently used in research and in practice, it has rarely been applied to urban agglomerations. The application of LDIE to urban agglomerations has important theoretical significance related to China’s new urbanization development strategy, the sustainable development of urban agglomerations, and the development and utilization patterns of land in China. Using existing research findings, this study applied LDIE and MCE-GIS to study SPUA and obtain the zoning categories of land spatial development intensity. The purpose of this study was to provide a new method for LDIE in China’s urban agglomerations and provide a basis for decision making regarding land spatial development.
4. Conclusions and Discussion
As stated by Stieglitz, urbanization in China and the development of new technology in the United States will be the two engines driving human development in the 21st century [50
]. For more than 30 years, urbanization in China has promoted the rapid development of the economy and society in China. Five major UAs (the Yangtze River Delta, Pearl River Delta, Beijing–Tianjin–Hebei, Chengdu-Chongqing, and Middle Reach of the Yangtze River UA) account for 9.06% of China’s area, 45% of the urban population, 50% of its GDP, 60% of fixed-asset investment, and 65% of the foreign direct investment in China. Therefore, urban agglomerations represent the core of China’s strategy for economic development. Meanwhile, China must deal with the pressures of a growing population, strain on resources, and environmental degradation, which are also faced by other developing counties. It is possible to formulate a scientific plan for the sustainable development of urban agglomerations if the environmental carrying capacity, the status quo, and the future development potential of urban agglomeration areas are considered. At the beginning of 2017, the State Council issued the “Several Opinions on Delineating and Strictly Protecting the Red Line of Ecological Protection” to upgrade ecological security to the institutional and legal levels. One of the key tasks of the newly MNR is to improve the quality of land use in urban agglomerations, that is, to optimize the land use structure and improve land use efficiency of urban agglomerations without reducing ecological security land.
The traditional LDIE technique methods [10
] with MCE-GIS pay more attention to the evaluation of land use intensity and development potential, but insufficient research on the current development efficiency. Therefore, we utilize a discriminant model of a three-dimensional matrix method composed of development intensity, supporting capacity, and utilization efficiency. The purpose of this method is to more scientifically and precisely identify problems related to land spatial development in urban agglomerations in order propose specific plans to improve land use quality. Then, based on the three-dimensional model, we obtained the zoning of national spatial development strength in the SPUA, China. The zones include key zones, stable zones, and restricted zones for development. The precise value of available construction land was calculated for each city in the SPUA. This method and evaluation result are highly consistent with the development needs of SPUA, and have been highly recognized by the Ministry of Natural Resources and the land administration department of SPUA. The research team was invited to give an academic report to the first National Symposium on Land Space Optimization Theory, Methods, and Practice organized by the Wuhan University and MNR in 25 November 2018 [52
Urban sprawl is a non-compact, low-density development urban form, often exhibiting scattered, leapfrog, strip, or ribbon structure, resulting in poor travel patterns and irreversible environmental threat. Spatial planning framework have important influence on leading the urban growth. Sprawl is acknowledged to have several negative impacts in European Unions’ territory, and smart and compact growth will be the future direction of urbanization [53
]. Tsilimigkas et al. considered that integrated spatial planning framework is very important for regulating the complex territorial issues raised in medium-sized cities [54
]. The urbanization model of self-promoted housing strategies could exploit loopholes and/or only partial application of the spatial planning framework and the very strict building regulations [55
]. This is also the case in China’s urbanization process. In order to explore the reform of the spatial planning system and build a national spatial planning system that is unified, interconnected, and hierarchically managed, the Central Office of the CPC Central Committee and the General Office of the State Council issued the “Provincial Space Planning Pilot Program” in January 2017, selecting Hainan and Ningxia. Jilin, Zhejiang, Fujian, Jiangxi, Henan, Guangxi, and Guizhou carried out provincial spatial planning pilots, coordinated various spatial planning, and prepared a unified provincial spatial planning. In April 2017, the Ministry of Land and Resources initiated the preparation of provincial land planning at the national level.
The state has officially approved nine urban agglomerations in the middle reaches of the Yangtze River, Harbin-Changchun, Chengdu-Chongqing, Yangtze River Delta, Central Plains, Beibu Gulf, Guanzhong Plain, Huhhot-Baotou-Erdos, Lanzhou-Xining, etc. The planning of the other 10 urban groups is being reported to the State Council according to procedures, and are awaiting replies. Coordinating provincial land planning and urban agglomeration planning, scientifically evaluating the quality of land use in urban agglomerations, is the basis for establishing the spatial planning system of “master plan-special plan-action plan”, and improving “national-provincial-urban-county-village”. This paper proposes development goals and paths based on the resource and environmental carrying capacity, land development potential, and efficiency of urban agglomeration. This method helps to break the balance of various spatial planning and can effectively link provincial and prefecture-level land space planning, realizing urban group space control from single-objective, rigid, static, to multi-objective, flexible, and dynamic development. We hope that this study will provide a reference for China’s urban agglomeration strategy and ideas for urban agglomeration policy makers in developing countries.
The article still has problems such as possible indicators for the multi-attribute evaluation system and uncertainty in the index weights is needed. In contrast, the identification method of spatial conflicts of new investment area [37
] and the method of landscape capacity assessment [48
] used in the same high-value landscape can better exploit the value of land. This method can complement our lack of research.
Different UAs have different development foundations, characteristics, and directions. The research method only discusses the land use quality evaluation of a coastal economic development type SPUA, which provides a reference for the evaluation of UA land use. The selection of evaluation indicators and weights is uncertain and cannot be directly used. Although insufficiencies remain, this study represents an exploration of the theory, method, and application of LDIE for urban agglomerations. As research continues, the theory and method will be gradually improved, and this paper will serve as a guide for the comprehensive, balanced, and sustainable development of urban agglomerations.