**1. Introduction**

Although the industrial revolution liberated human productivity, it was destined to intensify the conflict between human development and the natural environment. The development of industry over the centuries has brought people an abundance of material resources, but at the same time has created serious environmental hazards. For example, industrial water pollution induces infant congenital anomalies [1]; plastic particles have entered the human body through the ecological cycle of land, sea and air [2,3]. The dangers of pollution have awakened humankind to the need to protect the environment and to promote sustainable development. In 2007, 50% of the world's population was urban, and by 2025 it is expected to be 60%. There is no doubt that cities will be the main carrier of human life [4], and the construction of sustainable cities is of grea<sup>t</sup> importance to sustainable development [5,6].

**Citation:** Chang, B.; Chen, L. Land Economic Efficiency and Improvement of Environmental Pollution in the Process of Sustainable Urbanization: Case of Eastern China. *Land* **2021**, *10*, 845. https://doi.org/ 10.3390/land10080845

Academic Editors: Maciej J. Nowak, Giancarlo Cotella and Przemysław Sleszy ´ ´ nski

Received: 22 June 2021 Accepted: 11 August 2021 Published: 12 August 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Sustainable cities were first formally proposed at the Second United Nations Conference on Humanity in 1996 and have a rich connotation: social connotation [7], resource connotation [8], economic connotation [9] and environmental connotation [10]. Sustainable cities are one of the current research hotspots. Although the research on sustainable cities in China started late, it has been relatively fruitful. The literature on sustainable cities in China from the perspective of economics is distinctive. There are studies from the perspective of scientific landscape of smart cities [11], applied case studies [12], studies based on the perspective of eco-cities and low-carbon cities [13] and studies measuring the level of sustainable cities [14]. In addition, there are many studies focusing on the environmental factors of sustainable cities, such as green infrastructure and urban living environment [15] and territorial spatial planning [16]. The environmental Kuznets curve (EKC) was originally used to explain the existence of an inverted U-shaped relationship between income and the environment [17,18], while scholars later extended the connotation of the EKC to the interrelationship between the economy and the environment [19]. Recently, many scholars have extended its connotation to the interrelationship between the economy and the environment. When a country has a low level of economic development, the growth of the economy brings environmental pollution due to the scale effect [20,21]. Additionally, because industrial development requires a large amount of energy, and one of the main sources of energy in China is carbon-based energy [22,23], this leads to the fact that economic development in China in the past was inevitably polluting the environment. Studies by Christmann and Taylor and Li and Gong have proved this view [24,25].

Land urbanization has a negative impact on urban eco-efficiency [26]. Thus, China's rapid urbanization [27,28] has left China with some hidden problems and contradictions: between the scarcity of land resources [29] and the growing demand for urban building land, and between the lack of land use efficiency and the growing demand for environmental protection [30–32]. Since land resources, economic development and environmental protection are all important for the development of sustainable cities, can they all benefit at the same time? Terrell found that economic growth can influence land use and thus reduce carbon emissions through the EKC [33]. Pontarollo and Muñoz found an inverted U-shaped curve relationship between land consumption and economic growth [34]. Pontarollo and Serpieri discussed EKC from the perspective of urban architecture [35]. In China, Chen examined the presence of EKC using CO2 emissions [36]. However, Wang and Ye argued that the increase in income cannot directly reduce pollution, but it needs to be achieved by improving energy efficiency and implementing carbon taxes [37]. There are scholars have also focused their perspectives on cities and found that smart cities have environmental improvement effects [38]. Liao et al. measured urban land use efficiency in the framework of sustainable cities [39]. Dong et al. clarified the interaction between LUE, industrial transformation and carbon emissions [40]. To some extent, these studies confirm that the triad of economy, land and environment can benefit simultaneously. However, there is a paucity of literature on the study of China, and their conclusions cannot be strongly supported.

In order to study land, economy and environment in the same framework, this study proposes and measures the land economic efficiency (Land\_EcoE) index based on the characteristics of the concepts of "economic benefit of land use" and "land use efficiency" (LUE). Economic benefit of land use emphasizes the value of goods and services that may be produced within a limited amount of land [41], focusing on the output dimension. Land use efficiency integrally reflects the degree of material circulation and energy exchange between the elements in the urban system, the overall system and the external environment, and is a direct reflection of the realization of land value in the process of urban economic development [42]. Based on the two concepts, Land\_EcoE not only contains the connotation of economic output, but also has the connotation of economic rationality (economic structure dimension) and economic growth potential (economic quality dimension).

In fact, the Communist Party of China and the Chinese governmen<sup>t</sup> have promptly realized that the past crude factor-driven development model cannot meet the needs of China's development in the new era and that green, healthy and sustainable development is the choice of the times. The "Ninth Five-Year Plan" period (1996–2000) put limits on energy consumption and pollution emissions. The "11th Five-Year Plan" (2006–2010) made environmental regulation a binding target for local governments. Innovation is the first driving force for development. For many years, China has been actively pursuing an economic transformation strategy towards an innovation-driven, intensive development model. Wang et al. measured the low-carbon development quality of 259 cities in China and found that the quality level was generally higher in the eastern region [43]. According to the above, the synergistic development of economy–land–environment is achievable. Then, is the synergistic development of economic–land–environmental aspects possible in eastern China, which is the first place to go for policies and economically developed regions [44]? Or will the increase in land economic efficiency and the improvement of environmental pollution occur simultaneously?

Through the aforementioned literature, it can be found that: first, sustainable cities are a current research hotspot, but in China, research on sustainable cities is relatively weak, and research from the economic and land dimensions still needs to be improved; second, there are abundant studies on the EKC, but there are few studies on LUE from multiple dimensions from an economic perspective, in order to study the land economic efficiency and environmental pollution improvement. Therefore, combining the abovementioned realistic background and the questions raised, this study includes the following hypotheses:

#### **Hypothesis 1 (H1).** *There is a positive correlation between the increase in land economic efficiency and the improvement of environmental pollution in eastern China.*

At the same time, Chong et al. emphasize the close correlation between China's economy and carbon emissions [23], considering that the eastern part of China was chosen as the subject of this study because it is the most prosperous. However, in reality, there are still some prefecture-level cities in eastern China that are relatively less developed. Therefore, on the basis of H1, this study further proposes the hypothesis that:

#### **Hypothesis 2 (H2).** *There is a positive relationship between the increase in land economic efficiency and the improvement of environmental pollution in the most economically developed group of cities in eastern China.*

The possible contributions of this paper are: first, with the changing situation in China, earlier studies on the interrelationship between the economy and the environment are no longer appropriate for the current China, and this paper complements this study. Second, few studies have examined the relationship between land use efficiency (i.e., land economic efficiency) and environmental improvement from an economic perspective. Third, unlike other indicator evaluation methods, this study empowers the land economic efficiency evaluation system with the help of the entropy method, which enables a multi-layered discussion of what Land\_EcoE is all about. Fourth, this study uses a combination of qualitative (data visualization) and quantitative (econometric modeling) methods to make the conclusions of the article more convincing.

The remainder of the paper is as follows: Section 2 provides a brief description of the subject of this paper and describes the methods that emerged from this study. Section 3 shows the variables involved in this study and their sources. The spatio-temporal evolution of carbon emissions and land economic efficiency is plotted and analyzed. Section 4 describes the empirical process and results of this study. Section 5 discusses the findings of the study. Section 6 concludes the paper and presents the policy implications of the study.

#### **2. Materials and Methods**
