1. Introduction
Land is an important material carrier for urban economic, ecological, and social development. The rational and efficient use of land is a fundamental way to alleviate resource difficulties, ensure economic prosperity, and achieve the sustainable development of land space. However, with the accelerating process of urbanization, the construction land scale has expanded rapidly. From 2000 to 2020, the urban construction land area in China increased by 163.89% (the data are from
China City Statistical Yearbook). The land area to be built in the development zone reached 67,000 hectares in 2020, and the idle land increased by nearly 40% compared with 2021 (
http://www.gov.cn/xinwen/2021-01/13/content_5579414.htm (accessed on 20 September 2021)). The rapid expansion of cities has caused increasingly serious problems, such as inefficient land use and the disorderly development of marginal areas [
1,
2,
3,
4]. At the same time, extensive land use also damages the ecological balance of cities. As the main source of new urban land, agricultural land can also produce a lot of emissions in the transformation process, aggravating urban environmental problems [
5,
6,
7]. There is little doubt that the problem of low efficiency and pollution caused by the disorderly expansion of cities has become the biggest obstacle to the realization of high-quality development in China.
In order to improve resource utilization efficiency and advocate a sustainable development mode, the Chinese government has introduced a series of policies and measures to improve the urban green development level, of which the low-carbon pilot policy has attracted much attention. In September 2007, China clearly advocated the development of a low-carbon economy at the 15th Asia–Pacific Economic Cooperation (APEC) leaders’ meeting. With the meeting as an opportunity, the National Development and Reform Commission issued the Notice on the National Low-Carbon City Pilot Work and the Notice on the Pilot Work of Low-Carbon Provinces and Cities in 2010, the Notice on the Second Batch of Low-Carbon Provinces and Cities in 2012, and the Notice on the Third Batch of National Low-Carbon Cities Pilot Work and 2017, and successively identified 80 cities, such as Shanghai, Tianjin, and Shenzhen, as national low-carbon pilot cities, leading the country in exploring a new model of low-carbon development. Since then, active exploration has been carried out all over the country. Jiangsu, Guangdong, Hubei The information is from Implementation Opinions of Jiangsu Government on Accelerating the Establishment and Improvement of a Green and Low-Carbon Recycling Development Economic System, the 14th Five-Year Plan on Ecological Civilization Construction in Guangdong, and the Implementation Plan for Green Buildings Creation in Hubei, respectively. Other provinces (prefecture-level cities) successively introduced action plans for low-carbon construction in terms of intensive land use, green buildings, and other aspects in order to comprehensively implement the green low-carbon development model.
With the deepening of the green development concept, the relationship between low-carbon policy and urban land green use is becoming closer [
8,
9,
10]. The low-carbon policy can not only reduce the carbon emissions of land use by optimizing the urban spatial structure [
11,
12] but also restrain urban expansion by increasing areas of urban green belts, thereby helping relieve the impact of climate change [
13], which has a more significant effect in larger cities [
14]. However, most of the existing studies focus on the measurement and spatio-temporal analysis of urban land green use efficiency itself from the perspective of low-carbon, and research on the influence mechanism and spatial spillover effect is relatively rare. Therefore, this study analyzes the impact of low-carbon pilot policy on urban land green use efficiency (ULGUE) in 266 Chinese cities by studying the following three issues: (1) Can the low-carbon pilot policy improve ULGUE? (2) If so, how is it implemented? (3) Is there a significant spatial spillover effect? By answering these questions, the current situation of green land use in China can be comprehensively evaluated, which is beneficial to establishing and improving the existing policy evaluation system. In addition, it can speed up the improvements regarding performance evaluations of low-carbon pilot policies and provide theoretical support for the expansion of low-carbon pilot policies. Finally, it will help to clarify the key urban development mechanism and accelerate the realization of sustainable development goals.
Building upon the concept of the Kuznets curve proposed by economist Simon Smith Kuznets in 1955, the relationship between environmental quality and per capita income was named the Environmental Kuznets Curve (EKC) by Panayotou in 1993. The prediction results of the above hypothesis had been confirmed by actual conditions in western countries; therefore, many scholars have tried to test its applicability in China in recent years. Due to China’s increasing attention to its own environmental problems, administrative units at different levels have been changing from an interactive game to cooperation, which has advanced the arrival of an “inflection point” for the inverted “U” curve. This not only helps China build strong confidence in dealing with environmental and development issues but also shows its exemplary role in global environmental protection and green transformation and development, which is also of great significance to other developing countries. Obviously, whether from the perspective of practice or research value, the problems derived from interregional development in China are no longer limited to the country itself, they are increasingly becoming major concerns for the whole world. The starting point of this study is very consistent with the above background. The study of the spatial spillover effect of low-carbon pilot policy provides strong support for understanding the importance of public policy in green development.
The rest is arranged as follows:
Section 2 reviews the relevant literature, which lays the vital foundations for the following mechanism analysis;
Section 3 theoretically analyzes the effect mechanism for ULGUE;
Section 4 provides the research design, research method, data resources, variable selection, etc.;
Section 5 gives our empirical analysis, including basic robustness and endogeneity tests;
Section 6 explores the impact mechanism and spatial spillover effect of low-carbon pilot policy on ULGUE; and
Section 7 shows our conclusions and relevant policy recommendations.
2. Literature Review
Fully understanding the concept, measurement methods, and driving factors of urban land green use efficiency is of great significance for testing the relationship between the low-carbon pilot policy and ULGUE. In terms of concept, ULGUE is the ratio of input factors (land and other factors) of the land use system and land use output (including economic and ecological values) under certain production technology conditions. This reveals that ULGUE emphasizes the coupling of economy and ecological environment, and this study takes into comprehensive consideration economic and environmental factors. Unlike the traditional land use efficiency (ULUE), which only takes economic benefits as “desirable” output, urban land green use efficiency (ULGUE) takes urban pollution index as “undesirable” output when ensuring the rationalization of input and output, and establishes a land use evaluation system combining efficiency and green factors [
15]. In terms of measurement methods, urban land use efficiency (ULUE) mostly uses multi-input methods to measure land use efficiency, such as data envelopment, entropy, and stochastic frontier analyses [
16,
17,
18,
19], relieving the difficulty of conducting a multi-dimensional evaluation. With the continuous development of a green concept and measurement model, social and environmental costs should also be considered on the basis of considering economic benefits. With the help of the Slacks-based measure (SBM) model, which measures super efficiency based on unexpected output and stochastic frontier analysis, pollution indicators, such as industrial “three wastes” and carbon emissions, are set as unexpected output to achieve a more comprehensive ULGUE measurement [
15,
19]. Therefore, the expression of ecological significance is strengthened while the land economic effect is focused on.
The driving factors are roughly divided into three categories: (1) Regional policy. The regional policy covers high-tech zone policies and special economic zone policies [
19,
20]. The local government integrates resources according to regional characteristics and strengthens the input–output ratio of unit land area. However, the regional policy sometimes has negative effects. “Land finance” has been proved to have a direct impact from improvement to inhibition on ULGUE, producing a spatial spillover effect, and the long-term effect is more obvious than the short-term effect [
21]. (2) Industry cluster. In the industry cluster process, two results of a cluster economy and cluster diseconomy emerge. In the process of an industry cluster, there will be two results, namely an agglomeration economy and agglomeration diseconomy, which will have positive and negative impacts on ULGUE. The cluster economy can be understood by Jacobs’ externality theory [
22], namely that the integrated development of different industries produces the knowledge spillover effect and innovation effect, which not only improve the productivity of enterprises but also promote the economic benefits of land. The cluster diseconomy means that based on the premise of scarcity regarding land resources, an excessive industry cluster will lead to problems, such as a rise in the land use costs of enterprises and a decline in ecological environment quality, resulting in a simultaneous reduction in land economic benefits and environmental benefits [
23]. (3) Social development. The existing studies have shown that population migration, urbanization, and regional economic integration are closely related to ULGUE [
24,
25,
26,
27]. In addition, urban infrastructure construction will also have a significant impact on ULGUE [
28,
29]. For example, the research of Xiao et al. [
29] shows that urban roads can effectively attract and accelerate factors flow, optimize the land use model, and improve ULGUE.
3. Effect Mechanism Analysis
As a basic human value, environmental protection has been recognized by the whole of society; therefore, it has become one of the basic political goals of government. The implementation of a low-carbon pilot policy can not only directly affect ULGUE through “emission reduction” and “greening”, it also indirectly affects ULGUE through technological and structural changes. In order to fully reveal the influence mechanism of low-carbon pilot projects on ULGUE, the direct effect and indirect effect will be analyzed below.
The low-carbon pilot policy directly affects ULGUE through “emission reduction” and “greening”. In terms of “emission reduction”, in low-carbon pilot areas, the government usually introduces strict environmental regulations to ensure that the wastes in the production procedures of enterprises in the region meet emission requirements. At this time, manufacturers tend to directly allocate parts of funds as pollution control expenditure, which encourages enterprises to make technological progress in pollution control and emission reduction, reduce pollution emissions, and increase ULGUE accordingly [
30]. In terms of “greening”, under the triple pressure of low-carbon targets and the assessment and public demand of the National Development and Reform Commission (NDRC), local governments in pilot areas tend to increase their investment in basic facilities, such as “urban green lungs”, while “reducing emissions”. Therefore, urban ecological resources will continue to be enriched, and the local environment will be improved with the acceleration of the decomposition and absorption of pollutants, promoting ULGUE progress [
31].
H1. The low-carbon pilot policy can significantly improve ULGUE.
The low-carbon pilot policy indirectly affects ULGUE through technological and structural effects. Through the technological effect, the low-carbon pilot policy can effectively improve the urban innovation level. Technological innovation is a key channel to improve resource allocation efficiency and labor production in the whole of society, meaning it is an important driving force for high-quality development [
32,
33,
34]. Combining the existing literature and economic logic, we found that the low-carbon pilot policy mainly promoted technological innovation through talent gathering and capital allocation effects. Regarding fund allocation, during the construction of low-carbon pilot cities, the local government at all levels adjusts the financial expenditure structure according to their own conditions, increases R&D subsidies for enterprises, and reduces taxes on innovative enterprises. While mitigating the costs and risks of innovation subjects, they convey positive information to society and promote regional scientific and technological innovation. Talent gathering is considerable because, as a direct factor input, talents are conducive to accelerating local independent innovation and catalyzing the green innovation process of enterprises. At the same time, as carriers of new knowledge and skills, innovators can effectively promote enterprises’ learning abilities, thereby transforming, integrating, and applying new technologies, while providing intellectual support for emissions reduction and efficiency increases. Technical innovation can effectively improve ULGUE [
35,
36]. First of all, scientific and technological innovation can effectively promote productivity increases. By improving economic development, the pilot cities enhanced their comprehensive strength, attracted more high-quality investment projects, and increased the intensity of input–output per unit area of land, improving ULGUE in low-carbon pilot cities. More importantly, high-end and new technologies can promote the rapid development of communication, energy, transportation, etc., constantly enhancing the urban accessibility and thereby increasing attractiveness for external investment. Therefore, increases in regional incomes lead to changes in land use structures, elevating ULGUE.
Through the structural effect, a low-carbon pilot policy can significantly optimize the urban industrial structure. The optimization of industrial structures is essential to improving resource allocation levels among industries and promoting the optimal ratio of input factors to output factors. The low-carbon pilot policy mainly optimizes the industrial structure through industrial transfer and industrial transformation. Regarding industrial transfer, according to the “Pollution Paradise Hypothesis”, the low-carbon pilot policy will lead to the transfer of high-pollution enterprises from pilot areas to non-pilot areas because more relaxed environmental policies in non-pilot areas can accommodate these enterprises [
37]. At the same time, due to policy restrictions, it is difficult for low-carbon pilot cities to undertake high-pollution enterprises transferred from other regions in order to optimize regional industrial structures. Next, according to existing studies, industrial transformation can be divided into externally driven and internally driven. Regarding externally driven transformation, according to the “Porter hypothesis” [
38], when regional economic development is high, the environmental standard of production can be improved accordingly, with only enterprises whose innovation cost is less than innovation income surviving, resulting in a regional industrial transfer. Regarding internally driven transformation, when the demand structure changes, a hasty industrial transfer will result in huge sunk costs and goodwill losses. Some enterprises will choose to make corresponding adjustments to their industrial structure and technology investment to cope with environmental changes, thus completing the process of regional industrial transformation. The optimization of the industrial structure can promote ULGUE. On the one hand, the non-renewable nature of land itself will lead to the competitive use of resources in the land market, increasing the price of land and enterprise production costs. As a result, the “crowding-out effect” of industrial restructuring will force enterprises with high-pollution and low-income levels to move away from the area. The economic and environmental benefits of the area and ULGUE will be improved [
29]. On the other hand, thanks to the development of information technology, production factors, development policies, and other information in various regions can be circulated at a high speed. Low-carbon pilot cities have a “magnetic attraction effect”, attracting industries with high input–output returns to continue to concentrate, resulting in a cluster effect. The proportion of land used by inefficient industries is reduced, promoting ULGUE. The effect mechanism, including direct and indirect effects, is shown in
Figure 1.
H2. Low-carbon pilot policies indirectly improve ULGUE through technological and structural effects.
However, the low-carbon pilot policy may also have a negative effect, leading to ULGUE reduction. On the one hand, harsh environmental protection policies have a negative impact on regional economic development [
39,
40]. For example, in their research, Martin et al. [
39] found that the implementation of differentiated “emission reduction” policies in the EU increased energy prices in the region, leading to higher production costs and thereby affecting the regional ULGUE. On the other hand, a perfect design and good intentions may not generate good results. Similarly, enterprises may also accelerate resource consumption and increase urban pollution emissions due to a fear that green economic policies could damage their future earnings [
41], resulting in ULGUE reduction.
The main reason for the divergence in the above studies lies in the differentiated approaches to achieving emission reduction goals. In foreign countries, in the view of emission reduction policies increasing the production costs of energy-intensive industries in the region, emission reduction regions will transfer carbon-intensive industries to neighboring regions in order to achieve the coexistence of emission reduction goals and profits maximization. This process will not only increase global greenhouse gas emissions but also affect economic benefits in emission reduction regions [
39]. This phenomenon is called carbon leakage, whereby emission reduction areas take measures that lead to carbon emission increases in other non-emission-reduction areas. The research has revealed that the European Union and other developed countries have produced a very serious “carbon leakage” phenomenon [
42], increasing carbon emissions in surrounding countries that are used to produce cheap export products, thereby implicating themselves in the development dilemma [
43,
44], resulting in difficulties for ULGUE improvement.
Different from other countries, China has incorporated environmental performance assessments into the hard indicators of local government performance assessments (
http://www.gov.cn/jrzg/2013-12/09/content_2545183.htm (accessed on 20 September 2021);
https://www.spp.gov.cn/dj/c100027/201711/t20171109_320723.shtml (accessed on 22 September 2021);
http://hzedz.hanzhong.gov.cn/jjkfqzf/gwhwj/201901/t20190119_565959.shtml (accessed on 22 September 2021)), which means that regional officials need to take into account environmental quality on the basis of regional economic development, which leads to the phenomenon that surrounding regions do not fully accept the carbon-intensive industries transferred from pilot areas. Other regions will force pilot cities to implement technology upgrades and industrial transformation while ensuring their own economic development and environmental benefits. While relieving the “carbon leakage” phenomenon in low-carbon pilot cities [
45], the policy promotes the common progress of ULGUE in China through the spillover effects of technological upgrading and industrial transformation [
46,
47,
48,
49,
50]. According to the International Energy Agency (IEA) report (
https://www.iea.org/reports/global-energy-review-co2-emissions-in-2021-2 (accessed on 22 September 2021)), the overall carbon emission intensity in China decreased by 40% compared with 2000, while its intensity in developed countries has only decreased by 3% since 2010, which also supports the above view of this study.
H3. The low-carbon pilot policy can produce the positive spillover effect to improve ULGUE in nearby areas.
7. Discussion
This study selected 266 cities at prefecture level and above as samples and adopted muti-period DID and SDM-DID models to investigate the impact of low-carbon pilot construction. The results show that the low-carbon pilot policy is able to improve the ULGUE of pilot cities through technical and structural effects and has a positive impact on the ULGUE of surrounding cities.
(1) Channel mechanism. First of all, the low-carbon pilot policy aims at drawing up low-carbon development planning, formulating supporting policies, and establishing an industrial system characterized by low-carbon emissions. Based on urban land green use, it is intended to speed up the optimization of urban industrial structure, so as to continuously reduce urban environmental pollution and resource consumption while increasing urban economic development scale, which refers to the dialectical unity of environment and development. More importantly, technological innovation, as a key channel to improve the productivity of the whole society, is an important driving force for green development. With the deepening of the implementation of low-carbon pilot policy, the capital and talent levels have been continuously improved, the cost and benefits beneath low-carbon production have been consistently rationalized, and the productivity and green development have been mutually promoted and improved.
(2) Spatial spillover. Firstly, due to its unique national condition, China has seen barriers to the “industrial transfer” between cities, namely that low-carbon pilot cities cannot transfer high-pollution enterprises to non-pilot cities arbitrarily, and that non-pilot cities tend to prudently accept carbon-intensive industries due to official promotion and policy limitations. Then, the unique “reverse driving” mechanism is formed to urge pilot and non-pilot cities to jointly improve urban green development levels, which the significantly positive results of
dids in
Table 10 have proved. This is helpful for China to embark on a civilized development path of production development, ensuring a rich life and sound ecology in the future. Secondly, the research exerts a vital impact on global climate change. Since the Kyoto Protocol in 1997, major developed countries have transferred a large number of carbon-intensive industries to developing countries in order to meet their own emission reduction standards. The phenomenon of “carbon leakage” has failed to make an obvious effect on the remission of global climate change. The low-carbon pilot policy in China has been proved to generate a significant effect on China’s overall green development. If this experience is applied to neighboring countries and even the world, more positive effects are to be seen on global climate change. However, the path to realize the combination of its operation mechanism and national conditions of each country, so as to exert more positive impacts on global climate change, is a notable direction for future research.
8. Conclusions and Suggestions
Based on the panel data of 266 prefecture-level cities from 2006 to 2019, this study used the low-carbon pilot policy in China as a quasi-natural experiment and established the multi-period difference-in-differences and SDM-DID models to verify that the construction of low-carbon pilot cities has a significant impact on ULGUE.
The specific conclusions are as follows: (1) In general, the construction of low-carbon pilot cities has a significantly positive impact on ULGUE. This conclusion is still valid after a series of robustness tests that objectively prove the feasibility of low-carbon-pilot city construction for promoting urban ecological, economic, and social benefits. (2) The impact of low-carbon pilot policies on ULGUE has both direct and indirect effects. The low-carbon pilot construction has been proved to directly improve ULGUE, and also indirectly improve ULGUE through technological and structural effects, indicating that the impact of low-carbon pilot city construction on ULGUE is multi-dimensional and multi-channel. (3) The construction of low-carbon pilot cities can not only improve local ULGUE, but also result in a significantly positive impact on nearby cities. Based on these conclusions, this study proposes the following suggestions:
- (1)
The low-carbon pilot policy diffusion is implemented steadily and orderly. The core of the pilot policy is to follow the gradual reform model, which is conducive to avoiding the uncontrollable risks caused by large-scale transformation while fostering the advance of green and efficient development models. The above conclusions have proved that the low-carbon pilot policy not only contributes to local ULGUE improvement but also has a significant spatial spillover effect to improve the ULGUE of neighboring cities. This shows that the low-carbon pilot policy has played a significant positive role in ensuring a city’s “green and efficiency” levels. Therefore, the pilot cities can summarize and condense their successful experiences, continuously expand the pilot scope of low-carbon cities, and gradually promote the policy to the whole country. Meanwhile, we should correctly grasp the positive spatial spillover effect generated by the construction of low-carbon pilot cities, promote cross-regional cooperation between cities, and strengthen the flow of green production factors among different cities to promote steady improvements in ULGUE and make important contributions to the realization of the “dual carbon” goal and global climate change objectives;
- (2)
The channel mechanism is used to provide path support for the further optimization of low-carbon pilot policies. From the perspective of effectively improving technological innovation and industrial structure, the low-carbon pilot policy will play a more far-reaching and lasting role in ULGUE through optimizing the role of low-carbon cities. On the one hand, the innovation support is supposed to be provided by increasing innovation investment, talent support, and infrastructure construction. Furthermore, the creation of an innovative atmosphere and improvements in urban innovation ability are to be achieved by building a knowledge-sharing platform and promoting the free flow of factor resources. On the other hand, it is necessary to reasonably plan industrial development goals and realize the effective transformation of secondary industry to tertiary industry, high-additional-valued industry to low-additional-valued industry, and high-pollution industry to low-carbon environmentally protective industry in the region, as well as improving large-scale industrial operations with the aid of provincial development parks and national high-tech industrial parks and other carriers to promote the transformation of regional industrial structure. Global climate change originates from the industrial revolution, including its effects on industrial structure changes and resource consumption. The further optimization of operation channels though a low-carbon pilot policy is certainly conducive to mitigating global climate change.
There are still several limitations in this study. First of all, due to the difficulty in obtaining data, such as greenhouse gas emissions and soil erosion, the unexpected output in ULGUE is only measured by using industrial wastes. There is still room for improvement in this study, regardless of whether it is infinitely close to the actual level. Therefore, future research should focus more on continuously improving the composite output index, so as to interpret ULGUE from a more comprehensive perspective. Secondly, the spatial effect verified by spatial Durbin difference model is jointly reflected by pilot cities and non-pilot cities, which leads to difficulties in stripping and quantifying the net effects of the pilot policy on non-pilot cities. In subsequent research, on the basis of continuously improving the ULGUE indicator system, we will pay more attention to the net effect of low-carbon pilot policy on non-pilot cities through more appropriate methods in order to help policy makers formulate relevant strategies and achieve sustainable urban development goals.