3.2.1. Coupling Degree (CD) of Composite System

According to the principle of entropy increase, the system always moves from order to disorder, and the process of entropy increase is irreversible. In the composite ecosystem, composed of urbanization and ecosystems, economic, social, and ecological subsystems continue to generate biomass cycles, energy flows, and information exchanges, promoting the evolution of the complex ecosystem towards disorder. According to the synergy theory, the synergy between elements leads to overall system identity, structural stability, Area, and Baiyin.

evolutionary ordering, and functional optimization, which are the main forces that slow down the entropy increase process. The CD is a comprehensive measure of system synergy. According to the calculation results and relevant research [45], the CD is between 0.6 and 0.8, indicating that the system is in the running-in stage; and if the CD is between 0.8 and 1.0, the system is in a high coupling stage. 0.8 and 1.0, the system is in a high coupling stage The CD between urbanization quality and ecosystem services in the LXUA was 0.793 in 2000 and 0.842 in 2020, with an overall growth of 6.18% over the past two decades. In terms of changes in each county, 31 counties in the urban agglomeration showed varying degrees of growth in coupling, with 11 counties rising from the grinding stage to the

The CD between urbanization quality and ecosystem services in the LXUA was 0.793 in 2000 and 0.842 in 2020, with an overall growth of 6.18% over the past two decades. In terms of changes in each county, 31 counties in the urban agglomeration showed varying degrees of growth in coupling, with 11 counties rising from the grinding stage to the highly coupled stage (Figure 10). The growth of the CD reflects the improvement of the internal order degree of the composite system, that the overall evolution trend of the subsystems is consistent, and that the interaction is close. The CD of the eight counties decreased, with a decrease of less than 5%, mainly located in the centers of various cities. After 2000, the quality of urbanization in such counties has steadily improved, but the population is relatively dense, the proportion of construction land is relatively high, the area of natural vegetation is small, and ecosystem services are in a downward trend. The development direction of subsystems is contrary, making the CD of composite systems show a downward trend. highly coupled stage (Figure 10). The growth of the CD reflects the improvement of the internal order degree of the composite system, that the overall evolution trend of the subsystems is consistent, and that the interaction is close. The CD of the eight counties decreased, with a decrease of less than 5%, mainly located in the centers of various cities. After 2000, the quality of urbanization in such counties has steadily improved, but the population is relatively dense, the proportion of construction land is relatively high, the area of natural vegetation is small, and ecosystem services are in a downward trend. The development direction of subsystems is contrary, making the CD of composite systems show a downward trend.

*Land* **2023**, *12*, x FOR PEER REVIEW 14 of 20

*3.2. Coupling and Coordination Relationship of Composite System* 

3.2.1. Coupling Degree (CD) of Composite System

affected by human activities. So, the ecological environment of the valley basin should be

The medium- and lower-value areas of ecosystem services were located in the northeast of the LXUA, including Baiyin and Yongdeng, Gaolan and Yuzhong of the Lanzhou urban area. Land use in this area was mainly farmland and grassland. This region is located at the northwest edge of the Longxi Loess Plateau and the transitional zone from the eastern extension of the Qilian Mountains to the Tengger Desert. In this region, the climate is relatively dry, the ground vegetation is sparse, and the ecosystem services are under great pressure. The lowest-value areas of ecosystem services were highly overlapped with the water area and unused and construction land. The western part of the urban agglomeration was scattered in the Mugetan Desert of Guinan, the Tala Beach of Gonghe, the sand island at the northeast of Qinghai Lake and the Longyang Lake at the boundary between Gonghe and Guinan. The lowest-value areas in the east were mainly located in the urban built-up areas of each city, including the main urban areas of Lanzhou, Lanzhou New

According to the principle of entropy increase, the system always moves from order

to disorder, and the process of entropy increase is irreversible. In the composite ecosystem, composed of urbanization and ecosystems, economic, social, and ecological subsystems continue to generate biomass cycles, energy flows, and information exchanges, promoting the evolution of the complex ecosystem towards disorder. According to the synergy theory, the synergy between elements leads to overall system identity, structural stability, evolutionary ordering, and functional optimization, which are the main forces that slow down the entropy increase process. The CD is a comprehensive measure of system

0.6 and 0.8, indicating that the system is in the running-in stage; and if the CD is between

effectively protected to reduce ecological damage and environmental pollution.

**Figure 10.** The coupling degree of composite ecosystem in LXUA in 2000 and 2020.

From the perspective of distribution pattern, in 2020, the CD of the Qinghai area in the west of the LXUA was higher than in the east. In 2020, there were 15 counties with a CD above 0.8, which were in a high coupling stage, mainly concentrated in Xining Haidong and Linxia urban areas. The CD of 24 counties was between 0.6 and 0.8, which indicates the running-in stage. The counties in the running-in stage can be divided into two categories in total. The first is Dingxi and Baiyin, which are affected by natural factors such as climate and terrain, and their ecosystem services are at a low level. Compared to the rapid development of urbanization, the ecosystem service capabilities centered on water conservation, soil conservation, carbon fixation and oxygen release have not been effectively improved, and even some regions have shown a downward trend. The low level of ecosystem services is the main reason affecting the CD of the system. The other is the counties in the southwest of the urban agglomeration, such as Guinan and Tongren. These areas are located in the Nature Preservation Zone of Sanjiangyuan, with abundant water resources, a wide variety of biological species, and a good ecological environment. In recent years, with the increase of national protection efforts and the promotion of relevant policies, the regional ecosystem service capacity has been significantly improved. However, due to the high altitude and relatively sparse population in this region, the development of urbanization is limited to some extent. The urbanization quality subsystem is significantly lagging behind the ecosystem service subsystem, and there is significant room for improvement in coupling.

## 3.2.2. Coupling Coordination Degree (CCD) of Composite System

The degree of coupling can better represent the overall order of the composite system and the strength of the interaction between the internal subsystems, but it is impossible to judge whether the coupling is benign; that is, when the quality of urbanization and the level of ecosystem services are low, a higher degree of coupling can still be obtained. The concept of ecological civilization emphasizes the interdependence and coexistence of production, life, and ecological development. If a subsystem in a composite system is in poor condition, it will affect the overall development of the system. Only when the two are at a high level and have a high degree of coupling can system coupling truly be achieved. The introduction of coordination as a comprehensive measure of coupling and development level can reflect the degree of order of the internal structure of the system and the accumulation of external scale. According to relevant research results, the coordination degree was divided into 10 intervals (Table 2), and the lowest scoring subsystem was defined as a lagging subsystem.



In 2000, the average coordination degree between urbanization quality and ecosystem service in 39 counties of the LXUA was 0.464. In 2020, it was 0.493, an overall increase of 6.25%. Among them, the ecosystem service index in 31 counties was lower than the urbanization quality index. The coordination degree of various counties ranged from 0.372 to 0.753, with a total of 11 counties higher than 0.5, including the intermediate coordination area Chengguan in Lanzhou urban area, the primary coordination area Qilihe and Anning, the central and western urban area of Xining, and 6 barely coordinated areas (Figure 11). Such counties belong to the central urban areas of various cities and are also the core and secondary core of the development of urban agglomerations. They have a relatively good industrial foundation and a densely distributed urban population. Under the strong impetus of regional urbanization, the overall coordination degree of the composite system is at a high level. At the same time, 7 lagging subsystems in 11 counties, including Chengguan, Anding, and Chengzhong, are ecosystem service subsystems, and there is significant room for improvement in regional ecosystem services. coordination area Chengguan in Lanzhou urban area, the primary coordination area Qilihe and Anning, the central and western urban area of Xining, and 6 barely coordinated areas (Figure 11). Such counties belong to the central urban areas of various cities and are also the core and secondary core of the development of urban agglomerations. They have a relatively good industrial foundation and a densely distributed urban population. Under the strong impetus of regional urbanization, the overall coordination degree of the composite system is at a high level. At the same time, 7 lagging subsystems in 11 counties, including Chengguan, Anding, and Chengzhong, are ecosystem service subsystems, and there is significant room for improvement in regional ecosystem services.

**Figure 11.** Coupling coordination degree of composite ecosystem in LXUA in 2000 and 2020. mainly engaged in raw materials and heavy chemicals, which were built during the "First **Figure 11.** Coupling coordination degree of composite ecosystem in LXUA in 2000 and 2020.

counties in the current urban agglomeration.

glomeration coordination level, its internal structure and external scale represent the overall state and development level of urban agglomeration. Except for Lintao, Weiyuan, and Datong, the urbanization quality index in the near-imbalance areas was significantly lower than the ecosystem service index. Based on the analysis of the status of subsystems and the degree of coupling, it was found that the key factor affecting the degree of coordination lies in the low comprehensive development score of the composite system, and more specifically, the low quality of urbanization. According to relevant indicators, the per capita GDP of the 24 counties on the brink of imbalance in 2020 was only about 60% of the national average. The proportion of high-tech industries is low, and the problems of industrial isomorphism and homogeneous competition in each county are more prominent. At the same time, the overall scale of each county is relatively small, mostly smalland medium-sized towns with less than 500,000 people, with many infrastructure weaknesses and low public service levels. Building a platform of distinctive and advantageous industries in counties, increasing their overall carrying capacity, and directing the orderly transfer of agricultural population are all essential to the high-quality development of

In addition to Baiyin and the intermediate, primary, and barely coordinated areas,

The four counties belong to the mild-disorder area, mainly distributed in Baiyin urban area in the northeast of the urban agglomeration, including Baiyin, Pingchuan, Jingyuan and Jingtai, and the lagging subsystems are all ecosystem service subsystems. The CD of the four counties with mild disorder was at a relatively low level among the 39 counties, and the overall level of ecosystem services was low. Baiyin is located in the northwest of the LXUA, adjacent to the Tengger Desert in the north. The climate is relatively dry, with an annual rainfall of 180~450 mm and annual evaporation of 1500~1600 mm, and the forest coverage rate of the city is only 5.30%. Located in the transitional zone from the Loess Plateau to the inland denuded plateau, the ground is broken. The surface is mostly covered with loess and mainly composed of silty sand, with developed vertical joints, high porosity, and weak corrosion resistance. The fine soil covering layer on the surface is relatively thin and has a loose structure, which is prone to wind erosion and poplar blowing. At the same time, the backbone enterprises in Baiyin are still enterprises

In addition to Baiyin and the intermediate, primary, and barely coordinated areas, the remaining 24 counties were on the verge of imbalance. As the main type of urban agglomeration coordination level, its internal structure and external scale represent the overall state and development level of urban agglomeration. Except for Lintao, Weiyuan, and Datong, the urbanization quality index in the near-imbalance areas was significantly lower than the ecosystem service index. Based on the analysis of the status of subsystems and the degree of coupling, it was found that the key factor affecting the degree of coordination lies in the low comprehensive development score of the composite system, and more specifically, the low quality of urbanization. According to relevant indicators, the per capita GDP of the 24 counties on the brink of imbalance in 2020 was only about 60% of the national average. The proportion of high-tech industries is low, and the problems of industrial isomorphism and homogeneous competition in each county are more prominent. At the same time, the overall scale of each county is relatively small, mostly small- and medium-sized towns with less than 500,000 people, with many infrastructure weaknesses and low public service levels. Building a platform of distinctive and advantageous industries in counties, increasing their overall carrying capacity, and directing the orderly transfer of agricultural population are all essential to the high-quality development of counties in the current urban agglomeration.

The four counties belong to the mild-disorder area, mainly distributed in Baiyin urban area in the northeast of the urban agglomeration, including Baiyin, Pingchuan, Jingyuan and Jingtai, and the lagging subsystems are all ecosystem service subsystems. The CD of the four counties with mild disorder was at a relatively low level among the 39 counties, and the overall level of ecosystem services was low. Baiyin is located in the northwest of the LXUA, adjacent to the Tengger Desert in the north. The climate is relatively dry, with an annual rainfall of 180~450 mm and annual evaporation of 1500~1600 mm, and the forest coverage rate of the city is only 5.30%. Located in the transitional zone from the Loess Plateau to the inland denuded plateau, the ground is broken. The surface is mostly covered with loess and mainly composed of silty sand, with developed vertical joints, high porosity, and weak corrosion resistance. The fine soil covering layer on the surface is relatively thin and has a loose structure, which is prone to wind erosion and poplar blowing. At the same time, the backbone enterprises in Baiyin are still enterprises mainly engaged in raw materials and heavy chemicals, which were built during the "First Five-Year Plan" and "Third Line" periods, with high-energy-consumption industries such as nonferrous metals, chemical industry, thermal power, and building materials accounting for about 90%. The tasks of energy conservation and carbon reduction are relatively arduous. Strengthening environmental governance and protection and promoting the transformation and upgrading of industrial structure are currently the top priorities for the sustainable development of mild-disorder areas.

#### **4. Discussion**

By comparing previous studies, we believe that evaluating the scale of urbanization solely from population, economy, and land is not comprehensive in Northwest China. The assessment must consider aspects such as people's living standards, environmental protection, infrastructure, public service, urban vitality, and urban–rural relations. More than 60% of counties had an urbanization quality below 0.4 in 2020, indicating that the overall quality of urbanization in the LXUA is still low. It is necessary to change the development mode of simply pursuing the urbanization scale and focus on improving the quality and efficiency of urbanization. In the current research, statistical indicators are often used to evaluate the environmental condition, which can lead to higher evaluation results, reduce the spatial continuity, and enhance the mutability of the data. It is hard to reflect the real ecological status of the region using the evaluation results. Based on multivariate data and the InVEST model, we found that the overall spatial pattern of ecosystem services in the LXUA shows an increasing trend from northeast to southwest, while the level of ecosystem services is relatively low in city-and-town concentrated areas. The two systems

in general show a "high coupling–low coordination" development status. This indicates that urbanization quality and ecosystem services are closely related, and the feedback effect is obvious in the northwest arid area. Many counties are still the antagonistic stage and the running-in stage between urbanization and ecosystems, and the overall coupling coordination degree is relatively low. It is necessary to reduce the negative impact of industry and life on ecosystems through policies, funds, technology, and other means.

The coupling mechanism between urbanization and ecosystems is very complex. This study starts from two aspects of urbanization quality and ecosystem services, and the evaluation and analysis of the composite system may still be incomplete. Subsequent research will continue to be supplemented and improved. The study area for this article is the LXUA. What are the different coupling mechanisms between this area and other regions? Whether the conclusions obtained in this study are applicable to other urban agglomerations, as well as other spatial scales at home and abroad, requires further research and verification in the future.

We found that there are significant differences in the development level of subsystems and the coupling coordination degree of composite systems in different regions. Each county should adopt measures suiting local conditions. The construction of public green space such as parkland, square land and urban protection greenbelt should be strengthened in the intermediate, primary, and barely coordinated areas. In addition, the regions also need to strengthen urban pollution control, promote waste recycling and low-carbon treatment, and improve urban resilience and ecological security guarantee capacity. Counties on the verge of disorder should rely on ecological security barriers such as the three-rivers source area and the Gannan Plateau, accelerate the construction of the ecological protection belt in the Upper Yellow River, and actively protect the Huangshui River, Datong River, Daban Mountains, Laji Mountains and other ecological corridors. Each county should actively improve its infrastructure and public services to enhance the quality of the county's residential environment. On the one hand, mild-disorder counties should strengthen their combat of desertification and water loss and governance of soil erosion, as well as reduce environmental risk and pollutant emissions. On the other hand, these counties should repair the abandoned mines, actively build the circular economy industrial system, and promote the green transformation of the economy and society.

#### **5. Conclusions**

This paper takes the LXUA in the Upper Yellow River as a case study area. We constructed a comprehensive evaluation index system for urbanization quality and ecosystem services. Through the exponential efficacy function model, the InVEST model and the coupling coordination model, we analyzed the respective development status of urbanization quality and ecosystem services in the LXUA and explored the coupling coordination relationship between them. This study is important to clarify the coevolution mechanism of the man–land areal system in the Upper Yellow River. The results of the study can pro-vide decision support and a theoretical basis for the ecological protection and high-quality development of the Yellow River Basin. The main conclusions are as follows:


**Author Contributions:** Conceptualization, W.Z. and P.S.; data curation, W.Z.; formal analysis, W.Z. and P.S.; funding acquisition, P.S.; investigation, W.Z. and Y.Y.; methodology, W.Z. and Y.W.; project administration, W.Z. and P.S.; resources, P.S.; software, W.Z.; supervision, P.S.; validation, P.S.; visualization, W.Z.; writing—original draft, W.Z.; writing—review and editing, P.S. and Y.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the National Natural Science Foundation of China (Grant Number: 41771130).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the first author.

**Acknowledgments:** We sincerely thank the reviewers for their helpful comments and suggestions about our manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **Abbreviations**


#### **References**


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