The Coupling and Coordination Relationship between Leisure Tourism and Ecological Environment: The Case of Ili Region in Xinjiang Province

: There is no doubt that a coupling relationship between leisure tourism and the ecological environment exists, but how to realize their coordinated development on that basis is much less clear. In this paper, taking Xinjiang’s Ili region as the research object, we ﬁrst established a leisure tourism and ecological environment evaluation index system using the mean-variance method to assign its weighting and then built a coupling coordination model. In this way, the coupling and coordination relationship between leisure tourism and the ecological environment of the Ili region over a recent 20-year period (2001–2020) was analyzed in depth. Our results show that the economic beneﬁt of leisure tourism and the efﬁciency of ecological environment protection contribute most, respectively, to the leisure tourism and ecological environment subsystems. During the study period, the coupling and coordination of leisure tourism and ecological environment system in the Ili area could be divided into ﬁve types, namely, “serious disorder-system balanced development”, “moderate disorder-leisure tourism lags”, “near disorder-leisure tourism lags”, “barely coordination-leisure tourism lags’, and “primary coordination-system balanced development”. The comprehensive development level of leisure tourism has exceeded that of the ecological environment, and prominent ecological and environmental problems have gradually arisen. Therefore, when vigorously developing leisure tourism, we should pay more attention to the ecological environment’s problems so as to realize the sustainable, coordinated development of the two.


Introduction
Leisure tourism generally refers to touristic activity that relies on both the resources and facilities of tourism to enjoy specific cultural landscapes and various service projects so as to fulfill leisure purposes [1]. Compared with ordinary tourism, leisure tourism is not concerned with the "ornamental", nor does it cater to the "remote" [2], instead focusing on both "ease" and "recreation" [3,4]. Accordingly, it pays more attention to the state of cultural creation, construction, and appreciation of tourists and emphasizes people's spiritual enjoyment [5]. Statistics show that, in 2019 alone, the number of Chinese tourists reached 6.06 billion, and tourism revenue totaled ca. CNY 6 trillion, with 28.25 million people directly employed in tourism, reaching 79.87 million, when including those indirectly employed, this accounting for 10.31% of China's entire employed population [6]. Evidently, tourism can promote the development of touristic areas, but this entails the co-occurring consumption of resources and use of the environment, which can adversely affect the ecological environment of touristic areas. At the same time, the Chinese government views the construction of a "beautiful China" as a national strategy, and certain policy mansion, and designated by UNESCO for its 'Oriental serenade' (or the prairie night birthplace). Additionally, there are many other historical and cultural attractions, including 3 and 20 scenic spots classed at the 5A and 4A levels, respectively. The Tianshan Mountains are listed among the world's natural heritage sites, and there are 363 species of wild animals and at least 2000 species of higher wild plants in the Ili region, which is recognized as one of the world's rare gene pools of natural biodiversity. Not only is it the largest oasis in Xinjiang, but the Ili region is also a pivotal ecological barrier against desertification in China. Altogether, these geographic aspects provide a superior natural environment for leisure tourism. Finally, in recent years, due to its beautiful natural scenery and long history and culture, the Silk Road is attracting many tourists for leisure activities and sightseeing. According to official statistics, in 2019 alone, the Ili region received 45.68 million tourists, accounting for 28.3% of those visiting Xinjiang province that year and the Ili region's tourism revenue was CNY 49.585 billion, accounting for 52% of its GDP. This means that leisure tourism has become an important force for economic growth in the Ili region. However, with the rapid development of leisure tourism and the increasing number of tourists, the ecological environment of Ili has been degraded to varying extents. Therefore, it is imperative to study the coordinated and coupling relationship between leisure tourism and the ecological environment in this region of China.

Analysis of the Coupling Mechanism of Leisure Tourism and Ecological Environment
Coupling is a concept of physics referring to the integration phenomenon between two or more systems through the interaction and influence of their internal mechanisms. On the basis of system dynamics, system theory, and synergy theory, the function, response, information, coordination, feedback, and formation mechanism of the system of things can be studied, this being mostly applied in the fields of geography, environmental Tourism resources are abundant in the Ili region. There are three national nature reserves and two autonomous-level nature reserves, along with the famous 'narla', 'tang bra', and 'kara jun tianshan' grasslands scenery. It is home to a famous city, the Ili general mansion, and designated by UNESCO for its 'Oriental serenade' (or the prairie night birthplace). Additionally, there are many other historical and cultural attractions, including 3 and 20 scenic spots classed at the 5A and 4A levels, respectively. The Tianshan Mountains are listed among the world's natural heritage sites, and there are 363 species of wild animals and at least 2000 species of higher wild plants in the Ili region, which is recognized as one of the world's rare gene pools of natural biodiversity. Not only is it the largest oasis in Xinjiang, but the Ili region is also a pivotal ecological barrier against desertification in China. Altogether, these geographic aspects provide a superior natural environment for leisure tourism. Finally, in recent years, due to its beautiful natural scenery and long history and culture, the Silk Road is attracting many tourists for leisure activities and sightseeing.
According to official statistics, in 2019 alone, the Ili region received 45.68 million tourists, accounting for 28.3% of those visiting Xinjiang province that year and the Ili region's tourism revenue was CNY 49.585 billion, accounting for 52% of its GDP. This means that leisure tourism has become an important force for economic growth in the Ili region. However, with the rapid development of leisure tourism and the increasing number of tourists, the ecological environment of Ili has been degraded to varying extents. Therefore, it is imperative to study the coordinated and coupling relationship between leisure tourism and the ecological environment in this region of China.

Analysis of the Coupling Mechanism of Leisure Tourism and Ecological Environment
Coupling is a concept of physics referring to the integration phenomenon between two or more systems through the interaction and influence of their internal mechanisms. On the basis of system dynamics, system theory, and synergy theory, the function, response, information, coordination, feedback, and formation mechanism of the system of things can be studied, this being mostly applied in the fields of geography, environmental science, and ecology [33,34]. The leisure tourism system and ecological environment system share a complex structure and extensive content. From the perspective of the human-earth relationship research, the interacting research subject (human) and environment (earth) constitute a complex and open human-earth system [35]. Leisure tourism is human-oriented, this activity being part of a suite of human activities, while the ecological environment is a narrow geographical environment. The theoretical basis for the coupling of leisure tourism and the ecological environment is the theory of human and land systems, whose coordinated development reflects the sustainable development of the human-land relationship. Hence, we presume that leisure tourism and the ecological environment are open and complex systems that can influence each other and even restrict each other [36].
Considering leisure tourism development's role in fostering an ecological environment, the most direct manifestation of the "beautiful China" goal would be an intact ecological environment, which is the goal and foundation of leisure tourism development. To be specific, leisure tourism development can promote regional economic growth and direct more funds into ecological environment protection; in tandem, the income generated by leisure tourism can improve the related technology used by the same tourism industry, in addition to optimizing the allocation of tourism resources and reducing the consumption of ecological resources. Conversely, however, the waste gas, wastewater, and solid waste generated by leisure and tourism activities and their service departments exert significant pressure on an ecological environment's health. The pronounced economic benefits of leisure tourism often spur relevant departments and enterprises to blindly develop tourism resources and overload their operational capacity, exerting further pressure that threatens the integrity of the ecological environment.
Regarding the ecological environment's role in developing leisure tourism, a beautiful natural environment is the cornerstone of leisure tourism development. To be specific, a healthy ecological environment constitutes key capital input for gaining the economic benefits of leisure tourism, and thus the development of leisure tourism strongly depends on the quality of its ecological environment [37]. Therefore, sound protection of the ecological environment can not only improve the quality of leisure tourism resources to varying degrees but also the satisfaction of tourists and their revalidation rate, thereby promoting leisure tourism's further development. However, when excessive development of leisure tourism exceeds the local ecological carrying capacity, it will eventually destroy the ecological environment, reducing the environmental support of the scenic spot and even inhibiting ongoing or future development of leisure tourism in the affected region.
To sum up, in the process of leisure tourism development, its ecological environment provides it with the necessary material basis and goal orientation. It follows that leisure tourism should be based on meeting the needs of the ecological environment via effective governance and protection. In this way, leisure tourism and the ecological environment comprise a two-system interaction whose mutual promotion, feedback, and integration together constitute a benign coordinated development of a coupling system. This coupling mechanism is outlined in Figure 2.

Index Selection
According to the coupling and coordination mechanism of leisure tourism and the ecological environment, these two components are complex systems, and the key to understanding their coupling evaluation is to establish a robust scientific index system. Following previous studies [12,[38][39][40][41] and adhering to the principles of scientificity, systematization, representativeness, and availability, we chose 15 indicators-of leisure tourism

Index Selection
According to the coupling and coordination mechanism of leisure tourism and the ecological environment, these two components are complex systems, and the key to understanding their coupling evaluation is to establish a robust scientific index system. Following previous studies [12,[38][39][40][41] and adhering to the principles of scientificity, systematization, representativeness, and availability, we chose 15 indicators-of leisure tourism resource quality, leisure tourism infrastructure, and leisure tourism economic benefit-to reflect the comprehensive level of leisure tourism development (see Table 1). The term 'comprehensive development level' refers to the numerical value calculated through multiple indicators and their weights within a certain system to measure the comprehensive development status of the system. In this study, the higher its value, the better the condition is; otherwise, the worse the condition is. For the ecological environment, its comprehensive development level was conveyed on the basis of three levels: pressure, protection investment, and protection benefit (see Table 2). For this, the ratio of the no. of A-level scenic spots to the no. of A-level scenic spots in the province was used.
Leisure and tourism infrastructure (0.2557) Tourism infrastructure investment (10 3 yuan), X 5 0.0913 Refers to the economic investment generated by the construction and purchase of fixed assets in the process of tourism development, as expressed by the total investment in various reconstruction, expansion, and new construction projects for scenic spots. Share of tourism revenue in GDP (%), X 10 0.0424 Expressed as the ratio of the total tourism revenue to the total local GDP.
Tourism income (10 3 yuan) X 11 0.0349 This is the total consumption (amount spent) of tourists at tourist attractions. Expressed as the ratio of the no. of people lifted out of poverty by tourism to the total no. of registered poor population.
Tourism employment rate (%), X 15 0.0974 The ratio between the no. of local tourists and the total no. of villagers aged 16 and above. Table 2. Eco-environment system assessment index system and its meaning as applied to the Ili region.

System Level Level 1 Indicators Secondary Indicators Secondary Index Weight
Index Interpretation Characterizes the pressure of household waste gas on the atmospheric environment, as reflected by the amount of waste gas discharged by residents.
Household garbage clearance volume (ten t), Y 3 0.0311 Characterizes the pressure of household garbage on the ecological environment, expressed as the amount of household garbage output that can be transported to the garbage consumption place or a transfer place.
Population density, Y 4 0.0823 This is the ratio of the total regional population to the total local area.
Pesticide application intensity (kg/hm 2 ), Y 5 0.0201 Characterizes the pressure of sightseeing agricultural production on the ecological environment, as expressed by the number of pesticides applied per hectare per year.
Strength of chemical fertilizer application (kg/hm 2 ), Y 6 0.0307 This describes the pressure of sightseeing agricultural production on the ecological environment, as expressed by the amount of fertilizer applied per hectare per year.
Investment in ecological and environmental protection (0.2864) Environmental protection investment index (%), Y 7 0.0809 Characterizes the investment adequacy of regional environmental management funds, as expressed by the ratio of regional environmental protection investment to GDP. Characterizes the greening status of the wasteland as the sum of the plantation area on the wasteland and the afforestation area sown by aircraft.
Tap water penetration rate in rural areas (%), Y 9 0.0675 The ratio of the population of regional tap water users to the total population of the region.
Garbage collection facilities (one), Y 10 0.0666 The total no. of garbage bins, garbage compression trucks, garbage transfer stations, etc.
Environmental protection efficiency (0.4568) Domestic sewage treatment rate (%), Y 11 0.0755 Characterizes the regional sewage treatment status, as expressed by the ratio of the regional sewage treatment capacity to the sewage discharge capacity.
Household waste disposal rate (%), Y 12 0.0775 Characterizes the regional garbage treatment using the ratio of the amount of treated domestic garbage to the total amount of domestic garbage.
Days with good air quality (%), Y 13 0.0700 Characterizes the regional air quality, as expressed by the ratio of days with good or above regional air quality to the total number of days in the year.
Qualified drinking water quality rate (%), Y 14 0.0667 Characterizes the water quality in the area using the ratio of the amount of water to the total amount of drinking water meeting the sanitation standard (GB5749).
Characterizes the species change state in the region, as reflected by the ratio between the no. of local plant species and the no. of plant species in the biogeographic area.
Vegetation coverage rate (%), Y 16 0.0719 The overall green space status of the study area is conveyed by the ratio of its vegetation area to its total land area.
Public green space area per capita (m 2 ), Y 17 0.0784 Expressed as the ratio of the green area of residential zones in the area to the total population of the area.

Index Weight Calculation
In the evaluation system, the role of each index differs, so the determination of their corresponding weight will figure prominently in the evaluation results. The methods for calculating index weightings mainly include the hierarchical analysis method, mean-variance method, and coefficient of variation method. Of these, the mean-variance method entails using the importance of an index random variable discrete program to judge the size of a given weight, which is widely used in multi-objective decision-making. The research began by selecting pertinent evaluation indices for the leisure tourism and ecological environment systems. Indices were selected based on their impact on the systems in question. The mean-variance method was employed to assign weights, with this method chosen for its effectiveness in providing a comprehensive evaluation by balancing both mean value and variance. The relevant methodologies and walkthrough can refer to previous research in Chongqing City [42]. The steps involved in obtaining this are as follows: (1) Unitless treatment of data indicators. Assemble the judgment matrix composed of n evaluation objects and an m index, for which when the indicator is positive, we obtain and when the indicator is negative, we obtain where X ab is the NO.b evaluation index value of the NO.a evaluation object; max(X ab ) is the maximum value of the NO.a evaluation object; and min(X ab ) is the minimum value of the NO.a evaluation object.
(2) Then, calculate the mean value of the random variables.
(3) And calculate the mean-variance in X i this way.
(4) Finally, calculate the weight value of the index X i .
The relevant data of the Ili region from 2001 to 2020 are substituted into Formulas (1)- (5), and the weight of each index of the leisure tourism system and ecological environment system are obtained. These are respectively given in Tables 1 and 2.

A Comprehensive Evaluation Model
Based on the standardized data and weight values (see above), the evaluation model was then established as follows: (1) Comprehensive development level of basic indicators (Y ij ).
(2) Comprehensive development level of first-level indicators (Y i ).
(3) Comprehensive development level of the subsystem (Y).
In the above three formulas, i is the year, j is the serial number of a given leisure tourism (or ecological environment) indicator, r ij is the standardized value of a given leisure tourism (or ecological environment) indicator, w j is the weight of each indicator, n is the number of basic indicators within the first-level indicators, and m is the number of first-level indicators within a subsystem. We used the three formulas to calculate the comprehensive development level of each of the two systems; the higher its value, the better the condition is; otherwise, the worse the condition is [43].

Coupled Coordination Degree Model
The term 'coupling degree' refers to the degree of interaction between systems or system elements. In the critical zone, the characteristics and laws of the change in the system's phase from disorder to order are determined by the coupling action and coordination degree. The term 'coupling coordination degree' refers to a measure that quantifies the integration level and interaction between two or more systems-in our study, the leisure tourism system and the ecological environment system. A higher degree indicates a stronger, balanced interplay, while a lower degree signifies weaker interaction and potential imbalances. Accordingly, the full model of leisure tourism and the ecological environment has two parts: a coupling degree model and a coupling coordination degree model. This is their specific formula: where C is the coupling value between leisure tourism and the ecological environment, C ∈ [0, 1]: when C = 0, there is no correlation between the two systems; when C = 1, the two systems are in a benign resonant coupling state, and the system will develop in a new orderly direction; f (U) denotes the comprehensive development level of leisure tourism and, likewise, g(E) denotes the comprehensive development level of the ecological environment. The 'g(E) − f (U)' is used in this study to represent the difference in the comprehensive development level of leisure tourism and ecological environment systems. The difference is within the threshold range, indicating a balanced system development.
If the value of leisure tourism is greater than that of the ecological environment and the exponential difference exceeds the threshold. In different time periods, however, the degree of coupling and coordination between leisure tourism and the ecological environment may differ. These discrepancies (or shifts) can be detected by constructing a model for the coupling and coordination between leisure tourism and the ecological environment. It is formulated as follows: where D is the coupling degree of leisure tourism and the ecological environment, T is the comprehensive coordination index of leisure tourism and ecological environment, and α and β represent the contribution rate of leisure tourism and ecological environment, respectively, such that α + β = 1. In this paper, we set α = β = 0.5, meaning that leisure tourism and the ecological environment are equally important contributors.

The Coupling-Type Division
Following the coordination types that are standard in physics and referring to previous studies [16,44,45], the results for the coupling types between leisure tourism and the ecological environment were divided into three categories and eight sub-categories. According to the specific situation of coupling degree D, the range of moderate and severe imbalance is doubled, as detailed in Table 3. Based on system science theory, if the exponential difference between leisure tourism and the ecological environment falls within the threshold range, overall system development is balanced; but if the value of leisure tourism is greater than that of the ecological environment and the exponential difference exceeds the threshold, this indicates that the ecological environment lags; conversely, if the value of leisure tourism is less than the ecological environment value and the exponential difference exceeds the threshold, this indicates that leisure tourism lags. In this study, the threshold was set to 0.1, resulting in 24 sub-categories. Table 3. Classification scheme used for the development of coupling of leisure tourism and the eco-environment.

Class Division Basis Sub-Category System Numerical Comparison Sub-Category Type
Harmonious development

Related Data Sources and Calculation
The relevant data studied in this paper mainly came from statistical data published in the Statistical Yearbook of Ili Kazakh Autonomous Prefecture (2002-2021); the Water Resources Bulletin of Ili Kazak Autonomous Prefecture (2002-2021); the Social and Economic Development Bulletin of Ili Kazakh Autonomous Prefecture (2002-2021); and the Culture and Tourism Bureau of Ili Kazak Autonomous Prefecture. Some data were obtained from the 2020 questionnaire survey and related literature data. For some missing data, this paper used the growth rate filling and sliding average method to calculate them.
Relevant original data were entered into Formulas (6)- (8) to quantify the leisure tourism and ecological environment subsystems and corresponding comprehensive levels, as shown in Figures 3-5. Those results were then used in Formulas (9)-(11) to derive the leisure tourism and ecological environment coupling coordination values based on type (as defined in Table 3). This was used to assess the temporal trend in the Ili region's leisure tourism and ecological environment coupling coordination type, as illustrated in Figure 6.

Analysis of Comprehensive Development Levels of Leisure Tourism and the Ecological Environment
As seen in Table 1, the first-level indicators of leisure tourism resource quality, leisure tourism infrastructure, and leisure tourism economic benefits are ranked according to the size of their weighted value, namely, the economic benefits of leisure tourism (0.4211) > the quality of leisure tourism resources (0.3232) > the leisure tourism infrastructure (0.2557). Evidently, the factor most affecting the comprehensive development level of leisure tourism is its economic benefits, followed by the quality of its resources and infrastructure. In the evaluation index system of leisure tourism, those indicators whose contribution share is large are the tourism employment rate (0.0974), the investment of tourism infrastructure (0.0913), the development level of national culture (0.0887), and the scale and abundance of tourism resources (0.0880). The pooled weight values of these four indicators account for 36.54% of the total weight; hence, during the study period, those four factors contributed to the rapid development of leisure tourism in the Ili region. Therefore, the relevant government agencies and leisure tourism planners should pay

Analysis of Comprehensive Development Levels of Leisure Tourism and the Ecological Environment
As seen in Table 1, the first-level indicators of leisure tourism resource quality, leisure tourism infrastructure, and leisure tourism economic benefits are ranked according to the size of their weighted value, namely, the economic benefits of leisure tourism (0.4211) > the quality of leisure tourism resources (0.3232) > the leisure tourism infrastructure (0.2557). Evidently, the factor most affecting the comprehensive development level of leisure tourism is its economic benefits, followed by the quality of its resources and infrastructure. In the evaluation index system of leisure tourism, those indicators whose contribution share is large are the tourism employment rate (0.0974), the investment of tourism infrastructure (0.0913), the development level of national culture (0.0887), and the scale and abundance of tourism resources (0.0880). The pooled weight values of these four indicators account for 36.54% of the total weight; hence, during the study period, those four factors contributed to the rapid development of leisure tourism in the Ili region. Therefore, the relevant government agencies and leisure tourism planners should pay

Analysis of Comprehensive Development Levels of Leisure Tourism and the Ecological Environment
As seen in Table 1, the first-level indicators of leisure tourism resource quality, leisure tourism infrastructure, and leisure tourism economic benefits are ranked according to the size of their weighted value, namely, the economic benefits of leisure tourism (0.4211) > the quality of leisure tourism resources (0.3232) > the leisure tourism infrastructure (0.2557). Evidently, the factor most affecting the comprehensive development level of leisure tourism is its economic benefits, followed by the quality of its resources and infrastructure. In the evaluation index system of leisure tourism, those indicators whose contribution share is large are the tourism employment rate (0.0974), the investment of tourism infrastructure (0.0913), the development level of national culture (0.0887), and the scale and abundance of tourism resources (0.0880). The pooled weight values of these four indicators account for 36.54% of the total weight; hence, during the study period, those four factors contributed to the rapid development of leisure tourism in the Ili region. Therefore, the relevant government agencies and leisure tourism planners should pay greater attention to the tourism employment rate; strive to do a good job in the construction of tourism infrastructure; improve the level of national culture development and the scale and abundance of tourism resources; and, adopt the appropriate leisure tourism development strategy. These four actions are strategically significant for ensuring the healthy development of leisure tourism in the Ili region.
As Table 2 shows, the efficacy of ecological environment protection (0.4568) has the largest weight in the comprehensive index system of ecological environment, so it has the largest impact on the latter's comprehensive development level, followed by ecological environment protection investment (0.2864) and ecological environment pressure (0.2568). Nonetheless, population density (0.0823), the environmental protection investment index (0.0809), per capita public green space area (0.0784), and household waste disposal rate (0.0775) each make a moderate contribution, with their pooled weight values accounting for 33.03% of the total weight. In general, the comprehensive development level of the ecological environment is most affected by two factors: its protection efficiency and protection investment. Accordingly, we may infer that the regional population consumes material and resource consumption in both social production and living activities, which discharges many pollutants in high amounts, which is seriously impairing the development of the regional ecological environment and leading to its alteration. Therefore, bolstering the investment in environmental protection, improving the treatment rate of household garbage, and expanding the per capita public green space area are powerful measures that should be implemented to enhance the level of comprehensive development of the Ili region's ecological environment.
As Figure 3 shows, from 2001 to 2019, the comprehensive level of the leisure tourism system in the Ili region was distinguished by an upward trend. This result demonstrates that in recent years the Ili region has attached substantial importance to fostering leisure tourism, whose resources are well-developed and utilized, having achieved certain economic benefits. In 2020, the overall level of the leisure tourism system declined slightly, mainly due to the impact of the global COVID-19 pandemic. In further analyzing the evolution of each subsystem of leisure tourism, we see that the quality of leisure tourism's resources and its economic benefits have been rising steadily from 2001 to 2020. Specifically, the economic benefits of leisure tourism have undergone the fastest growth, which is consistent with it being responsible for the largest contribution to the comprehensive development of leisure tourism. The quality of leisure tourism resources has gradually improved, especially after 2011, when the first 5A-level scenic spot was designated in the Ili region. By 2020, it harbored three 5A-level scenic spots, with the number of 4A-level scenic spots reaching 20, thus increasing their popularity with tourists. From 2001 to 2011, its expansion was rather slow, but its growth rose rapidly from 2012 to 2017. After modest growth in 2018, it underwent a significant decline from 2019 to 202. This pattern suggests that the construction of leisure tourism infrastructure in the Ili region should shift from quantitative growth to qualitative improvement.
As seen in Figure 4, during the 20-year study period, the comprehensive level of the ecological environment system in the Ili region showed a trend of increasing development that was approximately linear since 2005. This shows that under the guiding concept of 'Lucid waters and lush mountains are invaluable assets', the Ili region greatly values the ecological environment's construction, in that its comprehensive level has continually improved in the 21st century. Regarding the trends in its subsystems for 2001-2020, the input subsystem and efficiency subsystem of the ecological environment have both risen in parallel, whereas the ecological environment pressure subsystem curve dips and fluctuates over the same period.

Analysis of the Coupling Results of Leisure Tourism and Ecological Environment System
As Figure 6 shows, the coupling and coordination of leisure tourism and the ecological environment system in the Ili region have increased almost 7-fold over the 20-year period (2001-2020). According to the classification scheme described in Table 3, combined with the Figures 5 and 6 trends, we may infer that the coupling and coordination of leisure tourism and the ecological environment system in the Ili area predominately consists of five types: (1) From 2001 to 2002, the coupling coordination degree value of leisure tourism and the ecological environment system in the Ili region nearly doubled, increasing from 0.0812 to 0.1596, with a g(E) − f (U) ≤ 0.1. So, according to Table 3, it belongs to the subtype 'major dysregulation-system balanced development'. During this brief period, the comprehensive level of the ecological environment system exceeded that of the leisure tourism system, and leisure tourism in the Ili region was not developed. This led to stark discordance between the leisure tourism system and the ecological environment system; (2) From 2003 to 2009, the comprehensive development levels of the leisure tourism system and the ecological environment system in the Ili region were on the rise (Figure 5), and the coupling coordination degree of the system likewise increased, from 0.2025 to 0.3916, with a g(E) − f (U) > 0.1. The coupling coordination type thus changed to 'moderate dysregulation-leisure tourism lags'. During this period, the government gradually paid attention to the development of leisure tourism and actively promoted the decision of 'promoting governance with awards', as proposed by the central government for the ecological environment, which promoted its better governance. Accordingly, the coupling and coordination degree value of the leisure tourism system and the ecological environment system steadily traversed the 'moderate imbalance-leisure tourism lags'; (3) From 2010 to 2013, the comprehensive development levels of the leisure tourism system and the ecological environment system in the Ili region continued their rise, with the coupling coordination value of the system increasing from 0.4070 to 0.4788, and a g(E) − f (U) > 0.1. Hence, the coupling coordination type shifted to the subtype 'on the verge of dysregulation-leisure tourism lags'. On the one hand, after years of efforts in the early stage of its leisure tourism development, the Ili region built a 5A-level scenic spot, the Nalati tourist scenic spot. At the same time, the province and its cities vigorously promoted Xinjiang's tourism resources, augmenting leisure tourism activity in the Ili region, which in turn hastened tourism's development. On the other hand, the region attached great importance to the construction and protection of the ecological environment, implementing its development strategy of 'ecological area, environmental protection first'. This further strengthened the development concept of giving priority to natural ecological protection in the Ili region. The leisure tourism system and the ecological environment system have simultaneously evolved, but the foundation of leisure tourism was weaker at this time, so it still lagged behind; (4) In the 2014 to 2016 period, the comprehensive development level of the leisure tourism system and the ecological environment system in the Ili region continued to mount. The coordination degree value of system coupling increased from 0.5034 to 0.5793, with a g(E) − f (U) > 0.1, and the coupling coordination type shifted to the subtype 'barely coordinated-leisure tourism lags'. During this short period, the development of leisure tourism was prioritized in that various counties and cities introduced measures to accelerate leisure tourism so that it would become the leading industry of the Ili region's economy. Concerning the ecological environment, the Overall Plan of Ili Prefecture (2012-2030) was formulated in 2014, which set forth and defined the construction goal of 'sustainable resource development and sustainable ecological environment'. Consequently, the leisure tourism system and ecological environment system were promoted into the subtype 'barely coordinated-leisure tourism lags'; (5) From 2017 to 2020, the comprehensive development level of the leisure tourism system and the ecological environment system in the Ili region rapidly rose, with the coupling coordination degree value of the system increasing from 0.6043 to 0.6668, with a g(E) − f (U) ≤ 0.1. Hence, the coupling coordination type became the subtype 'primary coordination-system balanced development'. Under the policy support of the '13th Five-Year Tourism Development Plan', and guided by the 'tourism+' and regional priority tourism development policy, during this period, the Ili region vigorously advanced its leisure tourism while also carrying out ecological environment construction. Thus, the type of coupling coordination was upgraded to 'primary coordination-system balanced development'. However, the trend curve in Figure 6 shows that from 2018 to 2019, the comprehensive development level of leisure tourism exceeded that of the ecological environment, indicating that ecological and environmental problems are gradually becoming prominent. Therefore, when vigorously developing leisure tourism, attention should be focused on resolving ecological, environmental problems, improving the quality of the ecological environment, and realizing fully coordinated development.
These results indicate the interdependence and mutual promotion between leisure tourism and the ecological environment. Ecological environment construction can provide a material foundation for leisure tourism, and the development of leisure tourism can promote ecological environment construction. This study analyzes the coupling and coordination relationship between leisure tourism and the ecological environment in the Ili region, which has important research significance. However, the spatial characteristics of various leisure tourism attractions in the Ili region, as well as the impact of factors such as the epidemic, cuisine, and stereotypes on local leisure tourism, have not been studied. The impact of these factors on leisure tourism has been confirmed by researchers in other regions [27][28][29][30][31]. This is the deficiency of this study and the problem to be solved in the next step.

Conclusions
In this study, the mean-variance method was used to calculate the weight value of each evaluation index, and a coupling and coordination model between leisure tourism and the ecological environment was built to analyze trends in their coupling and coordination relationships from 2001 to 2020. The largest contributing component (i.e., highest proportion value) to the leisure tourism system and ecological environment system is, respectively, the former's economic benefit and the latter's protection efficiency. For the leisure tourism system, the key indicators (having the largest proportion) are the tourism employment rate, tourism infrastructure investment, the level of national culture development, and the scale and abundance of tourism resources. For the ecological environment system, the key indicators are population density, environmental protection investment index, per capita public green space area, and household waste disposal rate. During the 2001-2020 study period, the coupling and coordination degree of leisure tourism and the ecological environment in the Ili region was distinguishable into five types. The comprehensive levels of leisure tourism and the ecological environment had similar trends. Leisure tourism's development can promote the construction of an ecological environment, and a more beautiful ecological environment can, in turn, improve the development of leisure tourism. On the one hand, we should strengthen the development of leisure tourism; on the other hand, we should increase the intensity of ecological environment protection and governance, further improve the quality of the ecological environment, and implement the coordinated development of leisure tourism and the ecological environment. Policymakers in the Ili region might consider strategies that promote sustainable tourism practices, such as investing in ecofriendly tourist infrastructure and implementing strict environmental standards for tourism activities. Overcoming potential challenges such as resistance from operators or financial constraints could involve comprehensive solutions such as public awareness campaigns about the benefits of sustainable tourism and financial incentives for eco-friendly practices. However, the study did not pay attention to the spatial characteristics of various leisure tourism attractions in the Ili region, as well as the impact of factors such as the epidemic, cuisine, and stereotypes on local leisure tourism. This is the deficiency of this study and the focus of the next step of research.