Uneven Distribution of Ecosystem Services along the Yarlung Zangbo River Basin in Tibet Reveals the Quest for Multi-Target Policies of Rural Development in Less-Favored Areas

Abstract

This study was conducted in the Qinghai-Tibet Plateau which is a typical less-favored ecologically fragile area. First, we constructed a GIS-based spatial gridding structure over the study area, the Yarlung Zangbo river basin in China’s Tibet, and used a value-assessment model to measure supply, support, regulation, and culture ecosystem services in each study grid. We then analyzed the spatiotemporal patterns of different ecosystem services in the region from 2000 to 2020. In addition, we conducted a spatial visualized analysis of the trade-off and synergies of multiple ecosystem services in each study grid. We found that: (1) On the temporal scale, from 2000 to 2020, the values of the four ecosystem services for supply, support, regulation, and culture along the basin demonstrated an upward trend. (2) On the spatial scale, the values of ecosystem services showed an uneven distribution, with a decline trend from east to west along the basin. (3) From the perspective of land use types, due to the large areas of water, grassland, and forest along the river basin, the ecosystem service values of the three types of land use ranked among the top levels. (4) The trade-offs and synergies between different ecosystem services and their spatial distribution along the river basin showed an uneven distribution pattern. The ecosystem services zoning revealed that the policies in guiding rural sustainability in the less-favored areas should adjust the measures to local conditions, it’s necessary to establish multiple targets across the entire region.

1. Introduction

Many efforts targeted at achieving rural sustainability in developing countries have been focused on highly favored regions. During recent decades, substantial progress in such regions has been made in increasing crop yields, income, and social development within favorable conditions in terms of environmental, societal, and natural resources, which can be readily integrated into national rural policies [1]. However, in less-favored areas, rural sustainable development appears to be lagging behind the highly favored regions. Due to geographic remoteness and agricultural and environmental constraints, degrees of rural poverty across the less-favored areas are essentially different [2]. Thus, developing a sustainable strategy in these rural areas represents a major challenge for policymakers. A typical less-favored area is characterized by uneven social, ecological, economic, and demographic distributions, which cause different developing paths presented by a combination of different livelihood strategies, ecological protections, and resource management regimes [2]. Such a characteristic implies that a one-for-all policy strategy cannot suffice to generate rural sustainable development.

The quantification of ecosystem services is a prerequisite for regional ecological protection measures, and a core of territorial spatial planning to implement rural development [3]. The ecosystem services comprise all the benefits that humans receive from ecosystems, including supply, regulation, support, and culture services, and their value assessment is fundamentally important for ecological protection, environmental economic accounting, and sustainable development [4]. This concept was first proposed by Wilson in 1970. Costanza conducted a more in-depth study on ecosystem services and their valuation methods in 1997 [5]. Since then, many studies have been conducted around this topic [6,7]. In 2005, a publication of the UN Millennium Ecosystem Assessment made clear that human beings have a close tie with ecosystem services and human well-being [8]. Further, it was recognized that ecosystem services are mutually constrained and cannot maximize benefits simultaneously because human claims have exceeded the limits of what the ecosystem can bear [9].

Based on the principles of ecosystem services, the essence of rural ecological revitalization is to realize a sustainable supply of rural ecosystem services [10]. However, the current approach to rural development focuses only on one type of service—supply—because this generates direct values for human demands such as food and raw materials [2]. The conflict between supply and demand for ecosystem services is becoming grave [11]. If we only focus on the supply service, and sacrifice other services to maximize the supply service, we may obtain some benefits in the short term. In the long term, however, this approach will inevitably affect the integrity of the structure and function of the rural ecosystem and eventually affect the implementation effect of rural development [12].

This suggests that the different types of ecosystem services interact with each other. The trade-offs and synergies are closely related to the level of demand for ecosystems [13]. Although the trade-offs and synergies among ecosystem services are prevalent at a global scale, they exhibit significant geographical variability and dynamic changes. Ecosystem service “trade-off” refers to a situation where the supply of one type of ecosystem service decreases due to the increase in other types of ecosystem services. On the other hand, there is a synergistic relationship between different types of ecosystem services, the “synergies” being situations in which two or more ecosystem services are simultaneously enhanced or reduced [14]. Currently, trade-offs and synergies in ecosystem services are usually analyzed in studies related to geography and ecology. There has been much less analysis of this kind linked to decision-making for rural developments in less-favored areas [15]. How to achieve rural sustainable development depends on the various resource capacities and economic developments, which are supposed to be optimally arranged by different policy packages focusing on different targets [12].

Thus, identifying the trade-offs and synergies among different rural ecosystem services is one of the core issues in decision-making for the optimal layout of rural revitalization. Among all types of ecosystem services, promoting rural ecological revitalization must be considered as a priority for implementing rural revitalization strategies and achieving comprehensive rural sustainability [16]. Under the current dual strategic needs of ecological civilization construction and rural revitalization, the synergistic development of ecological protection, economic development, and cultural revitalization can be ensured through scientific identification and benefit transformation of rural ecosystem values. Ecosystem services, as a theoretical model for realizing the transformation of ecological values and human benefits, represents a fundamental theoretical and practical methodological reference [17].

We took the Yarlung Zangbo river in Tibet as a study area to analyze the spatial and temporal patterns of ecosystem services and their implications for the layouts of rural revitalization in less-favored areas. The Yarlung Zangbo river is the highest river in China. The river is an important water source, and its valley is an important plateau agricultural and pastoral area [18]. However, the river basin is extremely sensitive to global climate change, and thus its eco-environment is fragile. Despite this, studies of the spatial and temporal dynamics of ecosystem services and their trade-offs and synergies along the Yarlung Zangbo river basin are rare [18]. At present, studies of ecosystem services along the basin are mostly focused on land-use change, geological hazards, and hydrological features of the river basin ecosystem with high anthropogenic disturbance. Thus, this study was motivated by the following research questions: (1) What are the spatial and temporal distribution patterns of ecosystem service values along the Yarlung Zangbo river basin? (2) What are the relationships between the different ecosystem services along the basin? (3) What do the distributions of ecosystem services and their trade-offs and synergies suggest for the policymakers regarding rural development and revitalization? To answer the questions, this study applied Gaodi Xie’s estimation model to calculate ecosystem services along the Yarlung Zangbo river basin during three periods in 2000, 2010, and 2020, and analyzed the changes in ecosystem service values during 20 years. The relationships involving trade-offs and synergies among different ecosystem services along the river basin were calculated by correlation analysis and spatially autocorrelated Moran’s I index. The results of the study can provide a scientific basis for policymaking in promoting rural revitalization and protecting ecological resources in Tibetan areas, as well as a study reference for the assessment of ecosystem services in other less-favored areas.

2. Materials and Methods

2.1. Study Area

The Yarlung Zangbo river originates from the northern foothills of the Himalayas in southwestern Tibet, and runs from west to east across southern Tibet, skirting the easternmost peak of the Himalayas at the Namcha Barwa Mountain and turning south to flow out of China. The Yarlung Zangbo river is defined as the longest highland river in China and one of the highest rivers in the world. The basin covers an area of 25.89 × 106 hm² and is located at 27–32° N and 81–98° E. The basin has many tributaries and is second only to the Yangtze river in China in terms of hydroelectric energy capacity. The annual precipitation along the basin is uneven. The upper reaches of the river are mainly recharged by snowmelt, with relatively low precipitation, while the middle and downstream reaches of the river receive more rainfall, especially the downstream areas, which are in the water vapor transport channel of the warm and humid air flow of the Indian Ocean, with high precipitation. The average annual temperature of the basin is 5–10 °C, the annual rainfall is 200–500 mm, and the average annual relative humidity is 40–50%. The basin is an ecological vulnerability and governance area in Tibet. According to the data (Figure 1), the land-use types of the basin are mainly grassland, forest, and desert. Due to the natural factor and limited human impact, the land-use change in the basin is small.

2.2. Data Sources

The land-use data in 2000, 2010, and 2020 used in this study were obtained from the European Space Agency (https://www.esa.int (accessed on 6 May 2022)) at a resolution of 30 m. The national sown area of rice, wheat, and corn as well as the revenue and expenditure per unit area data for the three periods of 2000, 2010 and 2020 were obtained from the China Statistical Yearbook and the National Compilation of Information on Costs and Returns of Agricultural Products.

There are some differences between the criteria for classifying land-use data and the classification in the ecosystem value-estimation model, and we needed to reclassify the land-use types. According to the ecosystem service equivalent value per unit area table proposed by Gaodi Xie, land use was classified into six categories: cropland, grassland, forest, water, desert and wetland.

2.3. Methods

2.3.1. Determination of Grid Scale in the Study Area

First, we built a spatial grid structure covering the study area. To determine the grid scale, the landscape diversity index of land types was used. The diversity index refers to the diversity of landscape elements or ecosystems in terms of structure, function, and change over time, and it reflects the richness and complexity of different landscape types. The calculation formula is as follows:

$$H=-{\displaystyle \sum _{i=1}^m\left(Pi\right)\left({\log }_{2}Pi\right)}$$

(1)

where H is the diversity index; Pi is the proportion of the area occupied by landscape type i; and m is the number of landscape types. A higher value of H indicates greater landscape diversity. Analysis shows that when the grid scale is larger than 35 km × 35 km, the rise in the diversity index of landscape types approaches an asymptote. Therefore, a grid of 35 km × 35 km size was selected as a basic spatial unit for subsequent analyses in this study.

2.3.2. Ecosystem Service Value-Estimation Model

1.

Standard unit equivalent factor analysis

The standard unit equivalent factor is the economic value of the annual natural food production of agricultural land with a national average yield of 1 hm² [19], and with this equivalent as a reference and combined with expert knowledge, the value of the standard unit equivalent factor of other ecosystem services can be determined, which can characterize and quantify the potential contribution capacity of different types of ecosystem service [19]. Referring to the ecosystem service assessment method proposed by Gaodi Xie and combining the standard unit area equivalent to modify the value of ecosystem services in the study area [20], the calculation formulas are:

$$D_z={\displaystyle \sum _{i=1}^n\frac{s_c{p}_c{q}_c}{s}}$$

(2)

$$ES{V}_z=D_z\cdot {\displaystyle \sum _{i=1}^n{\displaystyle \sum _{j=1}^m\left(b{e}_{ij}\cdot s_i\right)}}$$

(3)

where $ES{V}_z$ is the ecosystem service value dollar at time z; $D_z$ is the unit standard equivalent factor value (yuan/hm⁻²); $s_c$, $q_c$ and $p_c$ are the sown area (hm²), net profit (yuan·kg⁻¹) and yield per unit area (kg·hm⁻²) of grain type c, respectively, and c is the three grain types rice, wheat and corn; s is the total sown area of grain (hm²); $b{e}_{ij}$ is the value of i land use type j ecosystem service type (

Table 1. Ecosystem service equivalent value per unit area.

Types of Ecosystem Services		Cropland	Forest	Grassland	Water	Desert	Wetland
supply service	Food Production	0.85	0.31	0.1	0.8	0.01	0.51
	Raw material production	0.4	0.71	0.14	0.23	0.03	0.5
	Water supply	0.02	0.37	0.08	8.29	0.02	2.59
regulation service	Gas regulation	0.67	2.35	0.51	0.77	0.11	1.9
	Climate regulation	0.36	7.03	1.34	2.29	0.1	3.6
	Environmental purification	0.1	1.99	0.44	5.55	0.31	3.6
	Hydrological regulation	0.27	3.51	0.98	102.24	0.21	24.23
support service	Soil Maintenance	1.03	2.86	0.62	0.93	0.13	2.31
	Nutrient cycle maintenance	0.12	0.22	0.05	0.07	0.01	0.18
	Biodiversity	0.13	2.6	0.56	2.55	0.12	7.87
culture service	Aesthetic landscape	0.06	1.14	0.25	1.89	0.05	4.73

); Si is the area of land use type i (hm²).

2.

Value Equivalent Factor analysis

Value equivalent factor per unit area is the basis for assessing the value of each ecosystem service in regional ecosystems, and it refers to the annual average value equivalence of each type of ecosystem service per unit area [19]. Therefore, this study adopted a base equivalence table of ecosystem service values in China developed by Gaodi Xie based on the ecosystem and socioeconomic developments of China [6].

According to the ecosystem service value per unit area equivalence table proposed by Gaodi Xie, land-use was classified into six categories: cropland, forest, grassland, water, desert, and wetland. In the ESA’s approach to land classification, the ecosystem service value of construction land is similar as that of desert, so construction land is classified as desert. Thus, we made the table of Ecosystem service equivalent value per unit area of the Yarlung Zangbo river basin in 2020 (

Table 2. Ecosystem service equivalent value per unit area of the Yarlung Zangbo river basin in 2020 (yuan∙hm⁻²).

Types of Ecosystem Services	First-Class Classification	Cropland	Forest	Grassland	Water	Desert	Wetland
Supply service	Food Production	3746.12	1366.23	440.72	3525.76	44.07	2247.67
	Raw material production	1762.88	3129.11	617.01	1013.66	132.22	2203.60
	Water supply	88.14	1630.66	352.58	36,535.69	88.14	11,414.65
Regulation service	Gas regulation	2952.82	10,356.92	2247.67	3393.54	484.79	8373.68
	Climate regulation	1586.59	30,982.62	5905.65	10,092.49	440.72	15,865.92
	Environmental purification	440.72	8770.33	1939.17	24,459.96	1366.23	15,865.92
	Hydrological regulation	1189.94	15,469.27	4319.06	450,592.13	925.51	106,786.46
Support service	Soil Maintenance	4539.42	12,604.59	2732.46	4098.70	572.94	10,180.63
	Nutrient cycle maintenance	528.86	969.58	220.36	308.50	44.07	793.30
	Biodiversity	572.94	11,458.72	2468.03	11,238.36	528.86	34,684.66
Culture service	Aesthetic landscape	264.43	5024.21	1101.80	8329.61	220.36	20,846.06

).

2.3.3. Correlation Analysis

Correlation analysis was used to determine the linear relationship between variables and to clarify the direction of correlation between two variables [5]. If the correlation has a strong positive relationship, it means the value is larger, the correlation is stronger. If the value is smaller, the correlation is weaker. A positive value, or positive correlation indicates that when one variable increases, the other also increases. A negative value, or negative correlation indicates that when one variable increases, the other decreases. The calculation formula is as follows:

$$R_{xy}=\frac{{\displaystyle \sum _{i=1}^n\left(x_i-\overline{x}\right)\left(y-\overline{y}\right)}}{\sqrt{{\displaystyle \sum _{i=1}^n{\left(x_i-\overline{x}\right)}^2\sqrt{{\left(y_i-\overline{y}\right)}^2}}}}$$

(4)

where $R_{xy}$ is the correlation coefficient; n is the number of samples; $x_i{y}_i$ are the i-th value of x, y, respectively; $\overline{x}$$\overline{y}$ is the average of the variables x, y, respectively.

2.3.4. Spatial Autocorrelation Analysis

According to the principles of the first law of geography, spatial phenomena are universally autocorrelated [21]. The method of spatial autocorrelation analysis is to indicate that similarity between two locations depends on the spatial distance between them, including both global spatial autocorrelation and local spatial autocorrelation, which is often expressed by Moran’s I index, with Moran’s value between plus and minus 1. A value of 0 indicates no spatial correlation, greater than 0 indicates a positive spatial correlation, and below 0 indicates negative spatial correlation. Bivariate autocorrelation shows five results: high-low clustering, high-high clustering, low-high clustering, low-low clustering, and non-significant clustering, where high-high clustering and low-low clustering spatial distribution characteristics indicate synergistic relationships among ecosystem services, while high-low clustering and low-high clustering spatial distribution characteristics indicate trade-off relationships among ecosystem services [22]. The equations are as follows:

$$I=\frac{n{\displaystyle \sum _{i=1}^n{\displaystyle \sum _{j=1}^n{w}_{ij}\left(x_i-\overline{x}\right)\left(x_j-\overline{x}\right)}}}{{\displaystyle \sum _{i=1}^n\left(x_i-\overline{x}\right)\left({\displaystyle {\sum }_i{\displaystyle {\sum }_j{w}_{ij}}}\right)}}$$

(5)

$$I_i=\frac{n\left(x_i-\overline{x}\right){\displaystyle \sum _{j=1}^n{w}_{ij}\left(x_i-\overline{x}\right)}}{{\displaystyle \sum _{i=1}^n\left(x_i-\overline{x}\right)}}$$

(6)

where n is the total number of grid cells; $x_i\left(x_j\right)$ is the risk value of grid cell; $\left(x_i-\overline{x}\right)$ is the deviation of the risk value from the mean value on the i-th grid cell; and $w_{ij}$ is the normalized spatial weight matrix.

2.4. Method Restrictions

In this study, we used the ecosystem service value-estimation model, and equivalent factor analysis. These quantitative approaches are simple and easy to operate. Because the approaches are common, results obtained by practical application can easily be compared with those from quantity-based evaluation methods. The approaches applied can achieve rapid accounting of ecosystem service values, but also have certain limitations [23]. Due to the complexity of ecosystems, there are significant differences in magnitude and type of service, which are influenced by various environmental and biological conditions [24].

3. Results

3.1. Dynamics of Ecosystem Service Values in the Yarlung Zangbo River Basin

As demonstrated in

Table 3. ESVs in the Yarlung Zangbo river basin from 2000 to 2020.

Types of Ecosystem Services	Ecosystem Service Value (108 yuan)
First-class classification	Second-class classification	2000	2010	2020
Supply service	Food Production	68.36	138.82	185.05
	Raw material production	87.78	178.12	241.25
	Water supply	258.93	533.03	683.54
Regulation service	Gas regulation	304.87	618.44	837.33
	Climate regulation	845.56	1717.04	2326.04
	Environmental purification	395.6	807.44	1068.28
	Hydrological regulation	3133.2	6450.01	8260.77
Support service	Soil Maintenance	370.62	751.72	1017.94
	Nutrient cycle maintenance	29.19	59.17	80.15
	Biodiversity	379.49	771.67	1036.89
Culture service	Aesthetic landscape	187.57	382.01	510.23

, the ESVs along the Yarlung Zangbo river basin showed an increasing trend from 2000 to 2020. In Figure 2, the ESV of each type of land-use from 2000 to 2020 showed an upwards trend, with watershed showing the highest increase. The ESV for water land was also shown to be the highest among all land-use types for 20 years. The ESV of grassland and forest land was second-highest, and the increase in grassland and forest land was also larger. This is mainly because the areas of grassland, water, and forest along the Yarlung Zangbo river basin are larger, while the areas of desert, wetland, and cropland are smaller. In addition, although the ESVs of desert, wetland, and cropland were lower, they showed an increasing trend.

In general, the values of ecosystem services along the Yarlung Zangbo river basin increased from 2000 to 2020. Furthermore, the value of each service increased due to the elevation of the equivalent factor. In the

Table 4. ESV of various land use in the Yarlung Zangbo river basin from 2000 to 2020.

Land-Use Classification	Ecosystem Service Value (108 yuan)
	2000	2010	2020
Cropland	2.27	3.38	6.00
Forest	1242.98	2558.42	3499.48
Grassland	1527.54	3054.53	4142.42
Water	3243.73	6698.95	8482.66
Desert	44.37	91.28	113.52
Wetland	0.27	0.92	3.37

, wetland and forest showed the highest increments in ecosystem service values, and only the forest and wetland increased among all the six land categories during the 20-year period, mainly due to increased ecological protection efforts in the whole Tibetan region, including the construction of a series of nature reserves. The other four land categories recorded various decreases or increases during the past 20 years. Among these, between 2000 and 2010, a decrease in cropland was observed as the largest, mainly due to the continuous expropriation of cropland to build towns to meet the development of industrialization in the Tibetan region during this period. However, between 2010 and 2020, cropland showed a significant increase, which is mainly due to the slowdown of urbanization and the strict requirements of the national policy on ecological red lines.

3.2. Grid-Based Spatial and Temporal Variation of Ecosystem Services in the Yarlung Zangbo River Basin

To identify the differences in ESVs within the entire Yarlung Zangbo river basin, a grid of 35 km × 35 km size was selected for this study. Therefore, the entire river basin was divided into 250 grids of 35 km × 35 km, and the ecosystem service values in each grid were calculated. In Figure 2, ESVs for the whole basin showed an increase from 2000 to 2020. In terms of spatial distribution of ecosystem services, the grids with higher ecosystem service values were mainly distributed in the eastern part of the basin, while the grids with lower ecosystem service values were mainly distributed in the western and central parts. A few grids in the central part of the basin showed higher ecosystem service values and an increasing trend compared to the western part. In general, the ESVs along the basin are unevenly distributed, in the order of: eastern > central > western parts of the basin.

3.3. Ecosystem Service Trade-Offs and Synergies in the Yarlung Zangbo River Basin

3.3.1. Correlations of Ecosystem Service Values in the Yarlung Zangbo River Basin

As shown in

Table 5. Correlation analyses of ecosystem services in the Yarlung Zangbo river basin.

Ecosystem Services	Supply Service			Regulation Service				Support Service			Culture Service
	Food Production	Raw material production	Water supply	Gas regulation	Climate regulation	Environmental purification	Hydrological regulation	Soil Maintenance	Nutrient cycle maintenance	Biodiversity	Aesthetic landscape
Food Production	1
Raw material production	0.612 **	1
Water supply	0.659 **	0.283 **	1
Gas regulation	0.590 **	0.973 **	0.259 **	1
Climate regulation	0.605 **	0.985 **	0.274 **	0.983 **	1
Environmental purification	0.830 **	0.467 **	0.813 **	0.442 **	0.458 **	1
Hydrological regulation	0.640 **	0.264 **	0.979 **	0.240 **	0.255 **	0.793 **	1
Soil Maintenance	0.587 **	0.970 **	0.256 **	0.997 **	0.981 **	0.440 **	0.237 **	1
Nutrient cycle maintenance	0.561 **	0.939 **	0.227 **	0.966 **	0.950 **	0.410 **	0.208 **	0.968 **	1
Biodiversity	0.846 **	0.761 **	0.522 **	0.737 **	0.752 **	0.705 **	0.503 **	0.734 **	0.705 **	1
Aesthetic landscape	0.929 **	0.659 **	0.624 **	0.635 **	0.650 **	0.805 **	0.605 **	0.632 **	0.603 **	0.898 **	1

** At the 0.01 level (two-tailed), the correlation is significant.

, the correlation matrix of the 11 ecosystem services in the Yarlung Zangbo river basin showed that correlations were at the significant level of p < 0.01. Overall, relationships between ecosystem services in the basin are dominated by synergistic relationships. The correlation of gas regulation with soil maintenance was the highest across the whole study area. Furthermore, the correlation between climate regulation and soil maintenance, as well as between climate regulation and raw material production, was also high. The correlation of water supply with nutrient cycle maintenance was identified as the lowest across the whole study area.

3.3.2. Spatial Agglomeration Characteristics along the Yarlung Zangbo River Basin

Since the spatial clustering characteristics of the Yarlung Zangbo river basin from 2000 to 2020 changed slightly, to provide an updated basis for river management, the spatial clustering map of the river basin in 2020 was analyzed in this study. Figure 3 shows that synergistic relationships were dominant within the Yarlung Zangbo river basin, while synergistic relationships were mainly distributed in the eastern and central-western parts of the basin. Trade-off relationships were rare and more dispersed across the study area. For grids showing trade-off relationships, the support-culture service showed the fewest number of grids, but the supply-support service demonstrated the most. For the grids showing synergistic relationships, the support-culture relationship showed the highest number of grids, while they were concentrated in the eastern part of the river basin.

4. Discussion

4.1. Ecosystem Services Are Unevenly Distributed across the Less-Favored Area in Tibet

Identifying the distribution of regional ecosystem services may help exposit the features of integrity and correlativity of the ecological–economical–societal complex system of the region under study. On a gridded spatial structure along the Yarlung Zangbo river basin, the distribution of ecosystem services was found to be uneven. In general, the areas with high ecosystem service values were concentrated in the eastern part of the basin, because the eastern part is mainly the downstream area of the river, which has a large altitude drop, and as the river lowers, the southward humid air flow enters the downstream area, making it hot and rainy with abundant vegetation. However, the value of ecosystem services in the central and western parts of the basin is low, as the western and central parts correspond to the upper and middle parts of the basin. The central part of the basin has a temperate highland climate, with annual precipitation mostly ranging from 300 to 600 mm, while the valleys in the western region receive less than 300 mm of annual precipitation. In particular, the ecological environment of the Yarlung Zangbo river headwaters region is fragile, and global climate change and disturbances from human agricultural and pastoral activity have led to the shrinkage of the originally fragile wetland system, degradation of pastures, and an increase in desertification, thus decreasing the function of water containment and soil conservation in the headwaters area [25].

The main reason for the uneven distribution of ecosystem services is due to the sharp differences in land-use patterns and climatic conditions. The basin is a fragile ecosystem of global significance. On the one hand, it is the maintenance base of plateau biodiversity. It’s the most important regional ethnic tourist and recreational site, and an important part of world culture, providing ecological goods and services to mankind. On the other hand, due to its variable and extreme climate, natural disasters and high altitude, the soil is infertile and plant growth is slow, making it extremely difficult to restore the plateau’s ecosystem once it has been damaged, thus making the sustainable development of the region a very difficult challenge. Thus, the dominant service type varies across the basin. The spatiotemporal dynamic analysis of various types of land use and ecosystem services along the basin can provide a scientific basis and study reference for evaluating the key ecosystem services for environmental improvement and ecological policy formulation in the study area [26]. On the one hand, in the eastern region of the basin with high ecosystem service values, both supply services and ecological protection are identified as the key services that are delivered. Because of higher intensity of land use, natural vegetation restoration and protection is a primary target for rural development in the region. On the other hand, in the central and western regions of the basin with low ecosystem service values, because of the less favored climatic conditions, the plateau ecosystem is fragile. Therefore, the central and western parts of the river basin must consider ecological restoration and protection as a priority. Rural developments in these regions need to take ecosystem stability, ecological security [27], ecological compensation [28], and ecological civilization construction into account [29]. Sustainable development and economic diversification depend on a sound environmental policy. It is crucial to address the challenges that China is now facing in terms of the protection of natural amenities and better management of ecological protection. The change in land use affects ecosystem services [30]. Ecological restorations mainly refer to the restoration and reconstruction of natural ecosystems that have been damaged by natural mutations and human activity. To restore ecological functions, local and central authorities in China have adopted improved policies, such as returning alpine grassland to grass, reducing excessive interference from human activity, and establishing a virtuous cycle of alpine and arid grassland ecosystems. In conclusion, regional advantages should be utilized on the scale of the whole watershed in which the spatial layouts of economic, social and ecological developments should be reasonably planned. Humans are not capable of restoring damaged natural systems, but we can help nature by putting together the basic plants and animals that an area needs, providing the basics and then allowing it to evolve naturally and eventually achieve restoration. The two developmental lines of ecology and economics should develop together. Furthermore, to promote the sustainable development of the region’s ecological environment, people’s awareness of ecological protection should be improved, and the sustainable development of the ecological environment should be promoted [22].

4.2. Rural Development Zoning Based on Uneven Distribution of Ecosystem Services’ Trade-Offs and Synergies

Synergies and trade-offs among ecosystem services are mainly influenced by the drivers of environmental change, along with policy intervention. Failure to account for these drivers can result in poorly informed management decisions and reduced ecosystem service provision. The analysis of the spatiotemporal distribution pattern of the relationships of trade-offs and synergies can help policymakers to tailor optimal solutions for rural sustainability [31]. Using the spatial grid-based map approach, our study localized changes of ecosystem services synergies and trade-offs, and spatially analyzed the relationships between ecosystem services along the Yarlung Zangbo river basin. The correlation analysis revealed that the four ecosystem service types along the river basin mainly showed synergistic relationships. Trade-offs were identified only in a small number of grids in the western part of the basin. In this study, the supply-support service occupied the largest number of trade-off grids, with distribution more dispersed compared to some other services. However, the synergistic grids were more concentrated, with the high-high model mainly in the eastern part of the basin. The reason is that the lower reaches of the river are rich in vegetation, with good hydrothermal conditions, and therefore have a higher value of ecosystem services. The low-low synergistic pattern was mainly located in the central and western part of the basin, along the middle and upper reaches of the river, where natural vegetation is in poor condition resulting in a fragile rural ecosystem.

Drivers of ecosystem services’ trade-offs and synergies include both anthropogenic and natural factors [32], which are often inextricably linked. Clarifying the relationships among regional ecosystem services can avoid unnecessary trade-off risks [33]. The most direct way that humans use and manage natural resources is to use land, and thus dramatically change land-cover types. However, different regions may involve varying land-use types and different magnitudes of natural and anthropogenic factors [34]. The impact of climate change and irrational human activity may cause an imbalance between ecosystem supply and support, and regulation of cultural services, which could trigger counterattack of ecosystem service. Through gridding and visualization analysis, our results revealed significant uneven spatial distribution of ecosystem services in the less-favored area along the Yarlung Zangbo river basin, by elucidating the spatiotemporal divergence of the trade-offs and synergies between ecosystem services [35]. We suggest that the less-favored areas should be zoned on the basis of different levels of ecosystem service provision, and rural development should be based on service zoning. The western part of the Yarlung Zangbo river basin should pay more attention to the ecological management. This area can be defined as an ecologically fragile zone, where the main aim for rural development is to find ways to restore the full function of the ecosystem. In the central and eastern regions, strong trade-offs were found, which indicates that ecological capacity is still strong enough to support other forms of development. Although the impact of anthropogenic disturbance, urbanization expansion, and agricultural production is strong, our results indicate that it has not yet damaged the ecosystem [36].

4.3. Implications of Heterogenous Policies for Rural Revitalization in the Less-Favored Areas

For policymakers, the spatiotemporal patterns and overall trends of the relationships between ecosystem services might be more useful than evaluating ecosystem services individually. In this study, rural development zoning based on spatial heterogeneity of ecosystem services’ trade-offs and synergies indicates that the policies for achieving rural revitalization in less-favored areas should adjust measures according to local conditions and establish multiple targets across the entire area.

Ecosystem service synergies and trade-offs that were identified in this study were primarily based on land-cover changes along the river basin, and therefore they facilitate the ecosystem services’ provisioning enhancement and land-cover development and planning by directing landcovers in different regions along the basin in favor of ecosystem services provisioning and nature conservation. This framework can be used as a form of optimal policy analysis of spatial regulation and land use.

Since the main relationship of ecosystem services in the Yarlung Zangbo river basin is still in synergistic mode, we suggest that land use should be managed primarily through a land-sharing strategy. Land sharing is similar to the concept of multifunctional land-use, which refers to an integrated land-use without division into uncultivated areas involving less-efficient land production methods, and thus helps to promote biodiversity conservation as well as agricultural production [37]. For the trade-off provided by arable and ecological land, the strategy of land sparing can be used to explore the complex functions of land, so that arable land can be used as an independent space to improve the supply of ecosystem services, and ecological land can be separately used as green space to maintain ecological functions [38]. Ecological poverty alleviation and ecological revitalization are internally consistent [39]. Furthermore, the trade-offs and synergies of ecosystem services can be combined with the hierarchical planning of cities, counties, and townships, with units at all levels cooperating in the implementation of ecological construction, and with the development of ecological environmental protection in accordance with local conditions, seeking different criteria for trade-offs between economic development and ecological restoration covering the less-favored area.

Ecological environment in the western part of the Yarlung Zangbo river basin is fragile and ecologically sensitive, while agricultural supply services are significantly reduced and agroecological degradation is severe. Based on the results of our spatial analysis of ecosystem services and relationships between different service types, the eastern edge of this region should be defined as an ecological red line for rural revitalization zoning. By delineating a red line from the perspective of the watershed ecosystem services, the entire less-favored area can be evenly developed by improving the quality of the ecological system and eliminating unreasonable development ignoring laws and regulations. Thus, we believe that rural revitalization in the western part of the Yarlung Zangbo river basin should be based on restoring the ecological environment, maintaining sustainability of the watershed ecosystem, and reducing disturbance from excessive agricultural production and human activity.

The rural revitalization strategy in China has planned a new order of rural governance, and a well-functioning rural governance system can effectively promote the modernization of the national governance system. Rural revitalization is a critical component of the Chinese government’s 2020–2025 work plan. In China, large areas are still in less-favored condition. The results of this study provide a basis for decision making to achieve the aim for the management of rural ecosystems and rural revitalization, not only in the Tibetan Plateau region but also in less-favored areas in China. Furthermore, the key policy challenges for rural development in less-favored areas should be focused on land use, service delivery, economic diversification, and environmental protection.

5. Conclusions

We started by analysing the spatial layout of watershed ecosystem services along the Yarlung Zangbo river basin and their potential distribution zoning. The results showed that the implementation of rural development and revitalization in less-favored areas should reflect regional differences and should not follow a uniform standard. The main conclusions are summarized as follows:

(1) During 20 years from 2000 to 2020, the total ESV of the Yarlung Zangbo river basin shows a continuous upward trend, although ESVs for individual ecosystem services vary. The ESVs for different service types in the Yarlung Zangbo river basin, ranked from high to low, are as follows: regulating service, supporting service, provisioning service, and cultural service.

(2) ESVs within the Yarlung Zangbo river basin show an uneven distribution pattern, in which the grids with higher ecosystem service values are mainly in the northeastern part of the basin, while grids with lower ecosystem service values are mainly in the western and central parts. The eastern part of the basin has the highest ecosystem output value and the highest strength synergy among different types of ecosystem services, indicating the best production, living and ecological synergy in the region.

(3) Relationships of ecosystem services in the Yarlung Zangbo river basin are mainly synergistic, where the synergistic relationships are mainly distributed in the eastern and central-western parts of the basin, and the trade-off relationships are rare and scattered over the entire area.

(4) In the context of systematically assessing the relationships of ecosystem services across the Yarlung Zangbo river basin, we suggest that rural revitalization in the less-favored areas should establish a red line for ecological protection. There can’t be a policy for the entire area. Solutions must be focused on heterogeneous policies for multiple targets for rural revitalization and development.