1. Introduction
The complex interaction between economic development and urban land use has always been the focus of global sustainable development. Although there is a big gap between developed and developing countries [
1], they are both faced with the problem that economic growth is not sustainable because of the rigid restriction of the total amount of urban land resources [
2]. The whole world chooses to implement green economic development and higher intensity urban land use to solve the unsustainable problem of the traditional economic development model. Since the 20th century, China’s economic development achievements have attracted worldwide attention. However, the reality is that China’s traditional economic development model of high pollution and extensive utilization still exists [
3,
4]. Economic development is strongly dependent on the development and utilization of land resources [
5], and the problems of high-intensity or unreasonable urban land use, such as the disorderly expansion of urban construction land, structural imbalance, and overall low level of resource allocation efficiency, are becoming increasingly prominent [
6,
7]. Realizing the benign interaction between urban land development and green economic development is a strategic task and an important path for China, which is in the transition stage to green and low-carbon development, both at present and for a long time in the future. At the same time, studying the interaction between green economic development and urban land use intensity, and summarizing China’s experience in the above aspects, can provide path reference and experience for other developing countries to achieve sustainable development.
Green economic efficiency (GEE) reflects the economic efficiency of a country or region after comprehensive consideration of resource depletion and environmental impact, and is directly related to the green economy development in the future [
8]. In the research on the measurement of GEE, existing studies incorporated the cost of environmental pollution control into the production function as an undesired output, and used the Solow residual value method to measure green economy productivity to judge whether a country or region could achieve green economic development [
9,
10,
11]. With the continuous deepening of the index system and method innovation research on GEE, scholars have selected indicators based on the traditional indicator system of labor, capital, resource input, economic expected output, and environmental pollution discharge as undesired output [
12], adding consideration for the input and output of factors such as technology and smog [
13]. The parametric method and the non-parametric method are two methods to measure green economy efficiency. Among them, the parameter method is used to measure the GEE by setting the specific form of the production function, and the more commonly used method is the stochastic frontier analysis method (SFA) [
14]. Nonparametric methods mainly refer to data envelopment analysis (DEA) and its derived models [
15,
16]. The DEA model can measure the GEE under multiple input factors and multiple input–output conditions, but it can easily lead to biased results because it cannot consider the influence of input–output slack variables. In recent years, scholars have mostly used the slack-based model (SBM) based on slack variables proposed by Tone (2001) [
17] and the super-efficient SBM model that can make up for the SBM model to measure the efficiency value of multiple decision-making units with a unit of 1 [
18].
Urban land development intensity (ULDI) is an index to comprehensively evaluate the status of urban land development and utilization, including the comprehensive characterization of the urban land development scale, urban land development benefits, and urban land development structure [
19,
20,
21,
22]. In the above definition, the actual performance of urban land development is the expansion of the scale of construction land and the reduction in cultivated land, forest land, water areas, etc. [
23,
24]. In this process, the same urban land development scale produces different functions and benefits because of different urban land-use structures [
25]. Scholars in various countries have reached a general consensus that the ULDI is an important part of the urban space management and control system, and its scientific measurement and evaluation analysis is an important path to optimize the urban land development pattern [
19,
26]. Under the background of this theoretical research, Chinese scholars have achieved quite rich results in the concept and connotation measurement of ULDI. There are usually two research approaches. The first is to use a single indicator, such as the proportion of regional construction land area to regional land area [
27], building density [
28], compactness [
29], and plot ratio [
30,
31] to measure ULDI. In recent years, scholars mainly directly use the proportion of the construction land area in the urban area to the total land area in the urban area to measure the urban land development intensity [
32]. The second is to construct an index system from multiple levels for comprehensive evaluation according to the characteristics of urban land development. For example, Wang et al. [
33] selected indicators from six aspects including construction land development intensity, population density, economy, ecological environment, infrastructure, and public service facility intensity to comprehensively evaluate the ULDI of typical Chinese cities. Liu Yanjun et al. [
34] constructed a theoretical analysis framework for ULDI including the level and extent of construction land use, population, and socio-economic bearing intensity in urban areas, and selected corresponding indicators from three aspects of quantity, structure, and benefit to measure ULDI in northeast China. Kong Xuesong et al. [
35] selected indicators from three aspects of urban land development density, development benefit, and development degree to measure and evaluate the ULDI of county-level units in Jiangsu Province.
Existing studies have explored the interaction between ULDI and GEE. Some scholars regard construction land scale and land-use structure changes as the dominant characteristics of urban land development [
36,
37] and focus on discussing the economic, social, and ecological benefits brought about by construction land scale changes and different urban land-use structures [
38,
39]. Changes in the scale of urban construction land can have a positive impact on the quality of the economy, society, and ecological environment in the development of green economy, but the rapid expansion of urban construction land has adversely affected the urban ecological environment and the lives of urban residents, thereby reducing the GEE [
40]. At the same time, the changes in social structure, economic structure, and ecological structure caused by green development economy will ultimately be reflected in the urban land-use structure and its changes [
41,
42]. Some scholars have also studied the impact of green economic development on the ULDI. Factor agglomeration and efficient allocation are typical features of GEE improvement [
43]. The agglomeration economy, technological innovation and investment expansion caused by the agglomeration of factors and the efficient allocation of resources significantly affect the ULDI. Scholars generally agree that industrial agglomeration, industrial structure upgrading, and technological innovation are the direct reasons that affect the optimization of urban land development [
44,
45,
46]. However, with the continuous agglomeration of factors, there may be a “crowding effect”, resulting in problems such as the intensification of the contradiction between man and land and the blind expansion of construction land [
47]. Scholars are also concerned about environmental regulation as an effective means for green economic development to influence urban land development [
48]. Environmental regulation plays a certain role in alleviating excessive or unreasonable urban land development through structural effects, innovation effects, spillover effects, etc., and improves the efficiency of resource allocation, thereby affecting the intensity of urban land development [
49,
50].
There is an interaction and mutual influence between ULDI and GEE. The optimization of urban land development can promote green economy development, and economic transformation and green development can also control the total scale of urban land development and optimize the pattern of urban land development. However, the existing research mainly studies the one-way effect of GEE on ULDI or ULDI on GEE. These studies have not given the dynamic relationship between GEE and ULDI, and the research on the interaction and response mechanism between GEE and ULDI is still insufficient. Therefore, the contribution of this paper is to construct the evaluation index system of GEE and ULDI, respectively, and expand the depth and breadth of existing research on the relationship between GEE and ULDI. This paper will take 283 prefecture-level and above cities in China as the research objects and select the sample data from 2003 to 2019. First, the paper uses the super-efficiency SBM model and the panel entropy method to measure GEE and ULDI, respectively, reveal their evolutionary characteristics, and preliminarily determine the relationship between the two. Second, the paper uses the panel vector autoregression (PVAR) model to explore the dynamic interaction mechanism between the two. Finally, policies and suggestions are put forward to better realize the good interaction and sustainable development between ULDI and GEE.
4. Discussion
This paper defines the ULDI including the urban construction land scale, the internal type of urban construction land, and the economic, social, ecological benefits of urban land development. It reflects the current important measures to realize the sustainable development of urban land development in China, that is, to control the disorderly expansion of the scale of construction land in breadth, to optimize the types of urban construction land through internal potential tapping to the limit, and to continuously improve the benefits of urban land development in depth. This provides a reference for other developing countries to pay attention to the ULDI in the process of development.
However, only the internal improvement of ULDI is effective in the short term, but unsustainable in the long run. The rapid growth of China’s economy depends on the direct pull of the wide supply of urban land. China is faced with the problem of insufficient capital in the early stage of economic development. China’s unique land system, with the compulsory low-cost land acquisition system and the government-monopolized state-owned land transfer system as the core arrangement, ensures a wide supply of land and makes land resource utilization a source of capital for economic development [
61]. A large amount of low-cost supply of land has become an important tool for local governments to attract investment and obtain more investment in fixed assets, and promote the development of local industrialization [
62,
63]. Especially after the reform of the tax-sharing system, local governments have obtained a large amount of land transfer income and tax by increasing the supply of urban development land, bringing a large amount of land fiscal revenue [
64]. Land fiscal revenue and land financing mortgage funds have become important sources of funds for local governments to realize infrastructure construction, and further attract the inflow of capital and talents [
65]. Land has become a factor of production as important as technology, capital, and labor in the process of economic development, and urban land development as a tool has created a miracle of economic growth in China.
Many problems have begun to emerge from this traditional economic development model accumulated with the extension of the time domain and the frequency domain. First, the economic development model that relies too much on land resource utilization is unsustainable because of the real constraints of a scarcity of land resources. In addition, the development model of land capitalization in which local governments bundle land transfer fees and reserve land mortgage financing has accumulated a lot of financial risks [
66]. These further inhibit economic growth and urbanization. Second, environmental problems such as carbon emissions and industrial pollutant emissions are significant. Local governments rely on low-cost land supply to attract a large number of low-end manufacturing industries with high energy consumption and high pollution, which has greatly promoted the process of industrialization. However, in the long run, enterprises with poor prospects and low production capacity squeeze land resources, and the “crowding out effect” of technology-intensive and capital-intensive high-value-added industries reduces industrial output value [
67]. Third, bound by the law of diminishing marginal returns, the economic output that can be brought about by an increase in unit land investment is becoming more and more limited, and the engine function of land driving economic growth and regulating economic rhythm begins to decline [
68]. Ultimately, China’s economy has to face the transformation of old and new economic growth drivers.
China chooses a green way of economic development. From 2003 to 2010, China transformed the traditional economic development model of high pollution and high energy consumption. During this period, China’s “Eleventh Five-Year Development” plan has placed emphasis and strategic arrangements on structural adjustment, energy conservation and emission reduction, and coordinated regional development. After comprehensively considering economic growth and resource environmental protection, the GEE has declined. From 2010 to 2016, with technological innovation, industrial restructuring, environmental regulation, and other measures, the GEE began to rise steadily. Since then, China’s green economy model has continued to make new achievements. Because there is a direct elastic mechanism of urban land development, unit land input will bring about an increase in output. Therefore, even if China’s economy completes the phased transformation of new and old kinetic energy, urban land development as a traditional economic growth kinetic energy still exists, and the scale of urban land development and its growth rate still needs to be maintained at a certain level. Moreover, the green economy development faces the dual goals of increasing total demand and improving efficiency [
69]. The increase in aggregate demand for economic development will inevitably lead to and coerce an increase in aggregate supply, that is, an increase in total economic output will inevitably lead to an increase in the scale or marginal output of capital, labor, and land [
70]. At the same time, urban land development faces the constraints of limited total land resources and conforms to the law of marginal diminishing returns to land. Only by ensuring the sustainability of ULDI can we achieve the level of total economic output and improve the GEE.
Therefore, our findings confirm that there is a mutual influence and mutual promotion between urban land development and green economic development. Land resources are an indispensable element of economic development. The driving effect of urban land development on economic development will not be significantly adjusted or changed. No matter what kind of economic development mode, the input of urban land resources is required. Under the green economic development model, the development of the green economy presents a strong self-adjustment mechanism, which can adjust itself according to the actual development situation to ensure the sustainable development of the green economy. In addition, through technological innovation, industrial structure transformation, and upgrading, etc. to improve the GEE, it can effectively promote the sustainability of urban land development and achieve a balance between urban land development and protection. To achieve sustainable development goals, whether it is for China or other developing countries, it is not sustainable to rely solely on the optimization within the urban land development system or within the economic development system, but to achieve a benign interaction and collaborative development between urban land development and green economy are promising.
5. Conclusions
This paper has explored the dynamic relationship between ULDI and GEE. It mainly draws the following two conclusions: (1) from 2003 to 2019, China’s ULDI and GEE showed a relatively obvious upward trend, and the increase in ULDI in the period of increasing GEE was larger than that in the period of declining GEE. The growth and evolution trend of ULDI and GEE has the characteristics of interaction and coordination. (2) There is a two-way interactive Granger causality between ULDI and GEE. The GMM model estimation results show that both ULDI and GEE have positive inertial growth and self-enhancement mechanisms. The interaction between GEE and ULDI has nonlinear characteristics, which is manifested as a positive cumulative effect on the time scale of the effect of GEE on ULDI, but the effect of ULDI on GEE only has a significant positive enhancement effect in the short term, but this contribution gradually weakened as the number of ULDI lag periods increased. From the results of impulse response analysis, ULDI has a positive response to GEE, which tends to be stable after reaching the highest value in the fourth period and has a significant positive enhancement effect in the long run. The results of impulse response analysis also showed that GEE also had a significant positive response to ULDI, and its impulse response showed a phased “U”-shaped fluctuation trajectory, and ULDI has a fluctuating promoting effect on GEE.
When discussing sustainable development issues from the perspective of urban land use and economic development, it is different from looking at issues from one side. Our novel research perspective is to examine the bidirectional dynamic relationship between GEE and ULDI. The empirical test based on the interaction and response mechanism between GEE and ULDI provides a basis for realizing the path of sustainable development by realizing the urban land development system, the green economic development system, and promoting the good mutual feedback evolution between the two. It can be seen that the development of ULDI can play a positive role in improving GEE. With the expansion of construction land scale, the adjustment of land-use type structure and the improvement of urban land development functions, the green economy development can be continuously promoted. However, when the ULDI reaches a certain level, its influence on GEE will continue to weaken or even have a negative impact. However, at the same time, when GEE is improved through technological innovation, industrial structure transformation, and upgrading, it can continuously optimize the urban land development structure and improve the comprehensive benefits of urban land development, and reduce the dependence of economic development on urban land resources to a greater extent. Similarly, when GEE increases to a certain range, its impact on ULDI will continue to weaken and eventually stabilize. This means that under the support of a certain ULDI, GEE has been improved to a certain level, a new balance has been achieved between ULDI and GEE, and the whole society is in a state of a virtuous circle of sustainable development. However, simply relying on the internal optimization of the urban land development system to improve the ULDI or relying on the internal optimization of the green economic development system to improve GEE is not sustainable. Regional sustainable development plans and policies should be formulated from the perspective of the coordinated development of urban land development and green economy according to their own development conditions.
Admittedly, this study has several limitations. For example, first, there are other indicators and methods for measuring the status quo of urban land development and green economy development. Even the existing index system in this paper also needs to be further supplemented and improved according to the actual situation of each country or city. Second, this study only considers the interactive response between green economic efficiency and urban land development intensity. Studies have shown that resource endowment, population size, and structural characteristics, policies, and regulations have significant impacts on urban land development intensity and green economic efficiency. The current study does not incorporate these factors into the analytical framework. Third, there are significant regional heterogeneities in the resource endowment conditions and social and economic development levels of various countries, and there may be regional differences in the interactive response effect between green economic efficiency and the intensity of national land and space development. Future research will explore the construction of a more scientific index system and method for measuring urban land development intensity and green economic efficiency, and incorporate regional heterogeneity into the study of the relationship between the two. It is also a future research direction to refine the internal dimension of green economic efficiency improvement and the internal dimension of urban land development intensity to reveal the interactive response mechanism between green economic efficiency and urban land development intensity at a deeper level.