Analysis of Ecosystem Protection and Sustainable Development Strategies—Evidence Based on the RWEQ Model on the Loess Plateau, China

Abstract

Environmental sustainability and high-quality development are global issues since soil deterioration and potential desertification are caused by human activities and global climate change, especially in arid and semi-arid areas. The Loess Plateau is one of the most severely eroded regions in the world. Since the “Grain for Green Program” was established on the Loess Plateau in the late 1990s as a result of the degradation of the soil, it has been an important state policy and demonstration project for ecological protection and sustainable development in China. Therefore, understanding the spatiotemporal changes of soil wind erosion, such as yearly and monthly fluctuations in various periods, under the scenarios of global climate change and human activities, is crucial for carrying out soil conservation initiatives in the Yellow River basin. The revised wind erosion equation (RWEQ) model was applied in this study to evaluate the dynamics of soil wind erosion on the Loess Plateau, China. The soil wind erosion was evaluated on the Loess Plateau from 1981 to 2019 to provide a creative idea for managing ecosystems at the regional scale. By examining the case of the Loess Plateau, we hope to be better able to comprehend the significance of putting environmental protection projects into action to enhance the ecological environment and the well-being of locals, as well as to offer recommendations for the future creation of effective and sustainable development strategies.

1. Introduction

Soil is essential for maintaining the normal operations of terrestrial ecosystems [1,2]. Soil erosion is a major global soil degradation threat to people’s well-being and the sustainability of life on our planet [3,4]. Soil wind erosion is one of the greatest and most pervasive environmental hazards in connection with the impact of global warming and human disturbance, and it has a significant impact on the long-term development of social economies [1,5]. Wind erosion is most common in arid and semi-arid areas where precipitation is scarce, vegetation is sparse, the wind is strong and frequent, and loose ground surface material is easily blown away by wind [6,7]. Soil wind erosion impacts local ecosystems by lowering water quality, increasing silt concentrations in the runoff, lowering effective reservoir levels, reducing agricultural productivity, flooding, and destroying habitats. [8,9,10]. The loss of soil due to wind erosion, which affects around 28% of the world’s land, is one of the primary causes of land degradation [11,12,13,14]. Some studies indicate that 60% of ecosystem services have been degraded globally over the last half a century as a result of population increases and economic development [15]. It is worth noting that the Loess Plateau has suffered greater severe soil erosion than anywhere else in the world, which poses a significant threat to high-quality development.

The process of soil wind erosion is influenced by human activities and physical factors (soil texture, soil type, physical properties, etc.), climate factors (precipitation, wind velocity), terrain factors (elevation, slope, aspect, shape, soil-ridge roughness in agricultural land, etc.), and vegetation cover and interactions between them [1,16,17]. There have been significant efforts to construct quantitative evaluations of wind erosion, which primarily fall into two categories: on-site measurement and off-site quantification empirical models [18]. The former is frequently used in small-scale regional or local tests, whereas the latter is utilized to assess zone erosion severity on a wide scale [1]. The revised wind erosion equation (RWEQ) model has been widely used to simulate erosion across the world, with numerous researches including soil characteristics and climatic conditions in northwest China’s dry and semi-arid regions [11,19,20,21]. The RWEQ was adopted for this work to assess and map wind erosion on the Loess Plateau because it employs a simple modeling process, has fewer input parameters, and can simulate wind erosion accurately to some extent.

The Loess Plateau region used to be the major agricultural plant utilization region in China [22]. Moreover, it is one of the areas in the globe that is most severely degraded by wind [23], with an average annual soil wind erosion modulus of 5~10 × 10³ t/km². One of the rivers with the largest sediment content in the world, the Yellow River, receives the majority of its sediment from land erosion. Soil wind erosion and tributary sediment inflows contribute significantly to the sedimentation of the Yellow River, which silts up the main channel [24,25]. The Loess Plateau, with desert areas widely distributed, occupies approximately 6.7% of the land area of China and it is one of the major sources of Asian sandstorms (Mongolia is the largest source of Asian sandstorms) [26]. On the Loess Plateau, the Grain for Green Program (GFGP) [27,28], the Green Great Wall Program (GGWP) [29], and the Natural Forest Conservation Program (NFCP) are some of the desertification prevention and control initiatives that the Chinese central government has implemented to enhance the environment and fight desertification. When the initiatives were put into place, did they have the intended impact of reducing wind erosion? Given that the rate of forest cover has grown from 5.1 percent in 1978 to 9.0 percent in 2001 and vegetation conditions have improved, some authors believe that the initiatives have been successful in preventing desertification and may have even lessened the severity of soil wind erosion. In contrast, several investigations have concluded that the Grain for Green Program’s (GFGP) effectiveness in preventing sandstorms should be called into doubt. However, due to the limitations of available data and the complexity of the model, there have been few studies on wind erosion over long periods of time on the Loess Plateau. As a result, it is uncertain how the geographical and temporal patterns of soil loss and retention, which are crucial for the Loess Plateau’s ecosystem services as well as sustainable social and economic development, affect the Loess Plateau.

The Loess Plateau includes the Ulan Buh Desert, the Kubuqi Desert, and the Mu Us Sandy Land and surrounding sandy lands, which are the places from where the sandstorms from northern China obtain their sand. Sandstorms originating from the Mu Us Desert carry degraded soil down the midstream of the Yellow River, increasing the concentration of silt there and having other detrimental ecological effects. These are currently a threat to the ecological security and sustainable development of the Beijing–Tianjin–Hebei region, Guanzhong Plain Urban agglomeration, Central Henan Urban Agglomeration, and the neighboring areas [30,31]. Therefore, in order to improve landscape patterns, habitat qualities, and ecosystem services, it is vital to evaluate how well desertification prevention and control strategies are working. According to the available research, there has been a noticeable trend in increased vegetation activity over the past several decades [1,32], but it is still unclear how vegetation restoration affects ecosystem services [33]. Additionally, little is known about the intricate relationships between soil erosion and the affecting variables such as land cover, soil type, climate, and plant cover. Therefore, the goals of this study were to (1) quantify and map soil loss due to wind erosion based on the RWEQ model; (2) examine the effects of climate variability and ecological restoration programs on the spatial patterns of soil wind erosion and the related temporal changes; and (3) discuss the implications of these ecological restoration and conservation programs for soil erosion control. The findings should be a valuable resource for evaluating soil erosion in dry and semi-arid regions as well as for controlling and preventing soil wind erosion.

2. Materials

2.1. Study Area

The Loess Plateau region (33.68–41.82 N, 100.85–114.55 E) covers an area of 6.48 × 10⁵ km² and has an elevation of 1094–1274 m, traversed by the upper and middle reaches of Yellow River, and represents 6.75% of the territory in China (Figure 1). The three main morphological types in the Loess Plateau are loess platforms, ridges, and hills, which are formed by the deposition and erosion of loess. The Gobi Desert and other nearby deserts provide the majority of the loess. During interglacial periods, the sediments were transported to the Loess Plateau by southeasterly prevailing winds and winter monsoon winds. Under the arid climate, sediments deposited on the plateau were gradually compacted to form the loess. The region is home to more than 8.5% of China’s population and has a population density of 168 people per square kilometer. To support the growing population, forests have been gradually converted into farmland because loess soils are ideal for agriculture, despite being susceptible to water and wind erosion. The delicate local ecosystems and natural resources have been under a great deal of stress as a result.

The Loess Plateau comprises nearly the whole of Shaanxi and Gansu provinces, as well as portions of Qinghai and Henan provinces, Ningxia, and the Inner Mongolia Autonomous Region. The Loess Plateau serves as an example of a transitional belt that is prone to both wind and water erosion. It is a zone where the plateau transitions into the Mu Us Desert and the loessal hilly region transitions into the Ordos Plateau [34]. The Loess Plateau is also situated in both arid and semi-arid climate zones, where the average annual temperature is 9.0 °C and ranges from 14.6 °C in the southeast to 12.6 °C in the northwest. The average annual precipitation is primarily in the form of seasonal rainfall and is 120 mm in the northwest and 760 mm in the southeast [33]. The topography is quite complicated, with some parts having steep slopes with gradients between 0 and 75° [1]. It features the deepest and biggest loess deposit location on the planet. From the northwest to the southeast, a succession of aeolian sand, sandy loess, typical loess, and clayey loess cover the surface of the Loess Plateau. This layer of extremely erodible loess has an average depth of 100 m [35]. The Loess Plateau is one of the most severely eroded regions in the world as a result of a combination of summertime torrential rainfall, steep slopes, little plant cover, and highly erodible loess soil.

2.2. Data Sources

The daily meteorological data, including wind velocity, precipitation, air temperature, etc., were obtained from the China Meteorological Data Service Center (http://data.cma.cn/ accessed on 20 September 2021) for the period 1981–2019. A total of 201 meteorological stations were selected including 75 stations within the Loess Plateau region and 126 auxiliary stations surrounding the study area. The soil texture data were obtained from the Harmonized World Soil Database (HWSD, https://www.fao.org/soils-portal/data-hub/soil-maps-and-databases/harmonized-world-soil-database-v12/en/ accessed on 20 September 2021). Normalized difference vegetation index (NDVI) products were obtained from NOAA National Centers for Environmental Information (https://www.ncei.noaa.gov/products/climate-data-records/normalized-difference-vegetation-index accessed on 20 September 2021). NDVI values were derived from surface reflectance estimates using data from the advanced very-high-resolution radiometer (AVHRR) in the red and near-infrared spectral regions. The NDVI products were plotted daily on a 0.05° by 0.05° grid from 1981–2019. The potential evapotranspiration (PET) data on the 0.05° by 0.05° grids were obtained from the gridded Climatic Research Unit Time-Series data version 4.04 (CRU TS4.04), which are monthly variations in climate during 1901–2019. Data on annual precipitation (https://www.resdc.cn/data.aspx?DATAID=229 accessed on 20 September 2021) and air temperature (https://www.resdc.cn/data.aspx?DATAID=228 accessed on 20 September 2021) were collected from the Chinese Academy of Sciences’ Institute of Geographic Sciences and Natural Resources Research. Land use and land cover datasets derived from the 1:100,000-scale National China Land Use/Cover Datasets with 1 km spatial resolution were obtained for the 1980s, 1990, 2000, 2005, 2010, 2015, and 2018 (https://data.tpdc.ac.cn/zh-hans/data/a75843b4-6591-4a69-a5e4-6f94099ddc2d/ accessed on 20 September 2021). All of the data were interpolated or resampled to a spatial resolution of 5 km in order to prevent scale-mismatching issues. The China Statistical Yearbook provided the socioeconomic information. (https://data.stats.gov.cn/english/publish.htm?sort=1 accessed on 20 September 2021).

2.3. Methods

We used the revised wind erosion equation (RWEQ) model to evaluate wind erosion in the Loess Plateau from 1981 to 2019. RWEQ is an empirical model used to estimate long-term soil loss due to wind erosion [36,37,38]. The RWEQ formula is as follows:

$$S_L=\frac{2Z}{S^2}{Q}_{max}\cdot e^{-{\left(\frac{Z}{S}\right)}^2}$$

(1)

$$Q_{max}=109.8\left(WF\times EF\times SCF\times K\times COG\right)$$

(2)

$$S=150.71{\left(WF\times EF\times SCF\times K\times COG\right)}^{-0.3711}$$

(3)

$$WF=\frac{ {\sum }_{i=1}^N{u}_2{\left(u_2-u_t\right)}^2\times N_d\rho \hspace{1em} }{N\times g}\times SW\times SD$$

(4)

$$\rho =348.0\left(\frac{1.013-0.1183H+0.0048H^2}{T}\right)$$

(5)

$$SW=\frac{E{T}_p-\left(R+I\right)\frac{R_d}{N_d}}{E{T}_p}$$

(6)

$$SD=1-P$$

(7)

$$EF=\frac{29.09+0.31Sa+0.17Si+0.33\frac{Sa}{Cl}-2.59OM-0.95CaC{O}_3}{100}$$

(8)

$$SCF=\frac{1}{1+0.0066{(Cl)}^2+0.021{(OM)}^2}$$

(9)

$$K=e^{(1.86K_r-2.41K_r{}^{0.934}-0.124C_{rr})}$$

(10)

$$COG=e^{-5.614\times c{c}^{0.7366}}$$

(11)

where S_L is the soil loss transported to a downwind distance of Z, kg/m². Z is the aeolian transport distance, m. Q_max is the maximum transport capacity, kg/m. S is the critical field length. WF is the weather factor calculated based on wind velocity, precipitation, daily average temperature, and kg/m. EF is the soil erodible factor, dimensionless. SCF is the crust factor, dimensionless. K is the soil roughness factor, dimensionless. COG is the combined vegetation factor, dimensionless. u₂ is the wind velocity at a height of 2 m, m/s. u_t is the threshold of wind velocity at which soil wind loss occurs at a height of 2 m, m/s. N_d is the number of days in a period (here it is 15 days); N is the observation frequency of wind velocity during a period, here it is 500; $\rho$ is the air density of the meteorological station, kg/m³; g is the gravitational acceleration of the meteorological station, m/s²; SW is the soil humidity factor, dimensionless; SD is the snow cover factor, dimensionless. T is the Kelvin temperature, K. ET_P is the potential evapotranspiration, mm. R is the precipitation, mm. R_d is the number of rainy days. P is the probability of snow cover greater than 25.4 mm (or 1 inch). Sa is the sand content, %. Si is the silt content, %. Cl is the clay content, %. OM is the organic matter content, %. CaCO₃ is the calcium carbonate content, %. Cl is the clay content, %. OM is the organic matter content, %.

Figure 2 shows the study framework. Firstly, we examined soil wind erosion spatiotemporal characteristics and intensity based on the RWEQ model. Secondly, the ecological impact of the wind erosion intensity on the soil quality and soil nutrients was also assessed. Thirdly, we examined the relationships between wind erosion and variables such as wind velocity, precipitation, and air temperature. Lastly, we followed a multi-perspective study of wind erosion to promote the sustainable management of regional landscape patterns.

3. Results

3.1. Land Cover Changes

Farmland accounted for 31.1%, woodland accounted for 14.1%, grassland accounted for 42.8%, wetland accounted for 1.4%, urban areas accounted for 4.2%, and bare land accounted for 6.4% of the Loess Plateau in 2018. During 1981–2018 (Figure 3), the land cover pattern was not stable on the Loess Plateau. As is shown in

Table 1. Transfer matrix of land use change 1981–2018 (km²).

1981\2018	Farmland	Woodland	Grassland	Wetland	Urban Areas	Bare Land
Farmland	14.75	0.38	2.02	0.1	0.84	0.06
Woodland	0.2	6.89	0.41	0.01	0.06	0.03
Grassland	1.92	0.53	20.67	0.08	0.36	0.38
Wetland	0.14	0.01	0.08	0.58	0.03	0.04
Urban areas	0.18	0.01	0.04	0	0.96	0
Bare land	0.15	0.05	0.64	0.04	0.08	3.07

, the highest proportion of the net increase in area was for urban areas, whose net increase in area was 13.2 × 10³ km². The main land changes were the transfer from farmland to grassland, grassland to farmland, farmland to urban areas, and bare land to grassland, which saw increases in area of 23.5 × 10³ km², 22.3 × 10³ km², 9.8 × 10³ km², and 7.4 × 10³ km², respectively.

Although the areas of grassland, wetland, and bare land decreased during the first two decades examined (1980–2000), farmland, woodland, and urban areas marginally increased. Although farmland, wetland, and bare land all had significant declines in area in the third decade (2000–2010), grassland and urban areas grew modestly.

3.2. Spatial-Temporal Characteristics of Annual Soil Wind Erosion Modulus

As shown in Figure 4, it is apparent that the intensity of wind erosion and the areas of occurrence have been steadily decreasing throughout the Loess Plateau and that the distribution of soil loss by the wind was not even. The wind erosion modulus in the southern irrigated area (Fen–Wei irrigated area) was the least severe and was the most severe in the northern desert area (the Kubuqi Desert and the Mu Us Sandy Land).

The average annual estimated wind erosion modulus ranged from 0 to 1.5 × 10⁵ t/km²/yr from 1981 to 2019. The average annual soil wind modulus of the Loess Plateau was reduced from 14.8 × 10³ t/km²/yr to 5.2 t/km²/yr (Figure 5). The wind erosion modulus reached its highest levels in the past four decades in 1988 and 1996 at 21.8 × 10³ t/km²/yr and 23.4 × 10³ t/km²/yr, respectively.

As shown in this study (Figure 5 and Figure 6), the intensity of wind erosion and the areas of occurrence have been steadily decreasing over time throughout the Loess Plateau. The results of the average annual wind erosion modulus every 10 years in four periods (Figure 6) revealed that the wind erosion loss in the eastern mountainous region of the Loess Plateau decreased significantly. The soil loss due to wind in the Mu Us Sandy Land also greatly improved. Furthermore, the soil conservation ecological function improved steadily over time in the farmland, grassland, and woodland in the southern part of the Loess Plateau. In general, areas suffering severe soil loss due to wind on the Loess Plateau are gradually reducing.

3.3. Spatial-Temporal Characteristics of Monthly Soil Wind Erosion Modulus

To analyze the monthly spatial-temporal characteristics of soil wind erosion on the Loess Plateau, we calculated the monthly variations (Figure 7) and spatial distribution of the wind erosion modulus on the Loess Plateau (Figure 8). Between November and May of the following year, the wind erosion modulus was relatively higher, with the wind erosion modulus exceeding 500 t/km². The monthly soil wind erosion modulus had the two highest peaks on the Loess Plateau, with the soil wind erosion modulus greater than 1500 t/km² in December and April. Moreover, the wind erosion modulus in April was nearly 500 t/km² larger than that in November. The wind erosion modulus was much lower in other months, all below 200 t/km², and was lowest from July to September, falling below 50 t/km².

Figure 8 shows that the wind erosion intensity followed the same pattern in different months as the average annual results, being the highest in the north and lowest in the south. The wind erosion decreased in the northeast from January to August, increasing only in November and December. The wind erosion in the Kubuqi Desert and Mu Us Sandy Land caused the wind erosion modulus to reach its maximum value in April. The wind erosion modulus reached its second peak in November due to the arable land in the northeast. The monthly variation in the wind erosion varied a lot in the Loess Plateau’s northeast and increased significantly from November to April due to there being a lot of arable land, the altitude being relatively high, and the land being bare from November to April. Furthermore, as illustrated in Figure 7, fine particle sizes (more than 60% of particle sizes between 0.05 and 0.005 mm) and soft textures intensified the fluctuations in the monthly changes in the soil wind erosion modulus. In other months, the lower wind velocity and growing crops reduced the risk of soil loss due to wind. The dynamic path of the monthly wind erosion modulus variation in the temporal and spatial characteristics was as follows: (1) it increased first in the south from September to October, then rapidly in the east from November to December; (2) it weakened first in the east and then gradually in the south from January to July of the following year; (3) in August of the following year, it was concentrated primarily in the Kubuqi Desert area and reached its minimum value for the whole period.

4. Discussion

4.1. The Factors That Influence Soil Wind Erosion

Due to the effects on wind velocity and precipitation, climate change and human activities are increasingly dominating wind erosion dynamics. Grazing, human-caused LUCC, and the execution of ecological restoration projects are the three main types of human activity. Since the 1980s, the intensity of population activities on the Loess Plateau has been rising, in which GDP, population, and construction land have been increasing [39]. However, the quality of the ecological environment has not degraded and has even greatly improved. Furthermore, several studies have proven the considerable effects of soil conservation services on the Loess Plateau [1,32,33]. We evaluated the correlation between the soil wind erosion modulus and the main driving factors based on the wind erosion simulation results from 1981 to 2019 using Pearson’s correlation analysis.

As shown in

Table 2. Pearson correlation coefficients between wind erosion modulus and biophysical factors.

	Wind Erosion Modulus
Wind velocity	0.909 **
Air temperature	0.373 *
Rainfall	0.783 **
Vegetation coverage	−0.535 **

** Correlation is significant at the 0.01 level (2-tailed) * Correlation is significant at the 0.05 level (2-tailed).

, the soil wind erosion modulus, wind velocity, air temperature, rainfall, and vegetation coverage all have a high association. This is the result of a combined effect of strong wind environments, sparse vegetation cover, and erodible soil [11]. The first three key factors are positively correlated with the wind erosion modulus and negatively correlated with vegetation coverage. Wind velocity is the most influential factor in wind erosion. Wind erosion loss can thus theoretically be reduced more dramatically by lowering wind velocity than by increasing vegetation coverage [40].

4.2. Relationship between Soil Wind Erosion and Ecological Rehabilitation Projects

Because of intense wind erosion, the Loess Plateau serves as both a location for the deposition of loess and a source of dust. Significant ecological and environmental hazards have been created by the escalating soil wind erosion. Soil wind erosion prevention and control, as well as promoting sustainable steppe management, are still important in the Loess Plateau. The government launched a number of ecological restoration initiatives, including the GFGP, the Three-North Shelterbelt Project, the Beijing–Tianjin Sandstorm Source Control Project, etc., to reduce soil erosion. From 1981 to 2019, a series of ecological restoration programs aimed at improving the natural environment were implemented on the Loess Plateau and some of these programs had a positive impact on some ecosystems. Since 1999, programs such as the NFCP, which aims to protect natural forests through logging bans, and the GFGP, as well as the conversion of farmland into woodland and grassland, have been implemented on the Loess Plateau. Concrete measures include the natural enclosure of grassland, reforestation, afforestation by aerial seeding or closing hills, conversion of farmland to woodland or grassland, and grassland management. In addition to the foregoing ecological conservation programs, soil and water conservation programs have also been implemented on the Loess Plateau and neighboring areas since the late 1950s [41] and include terrace and dam construction, afforestation, etc.

Urban growth, climate change, and ecological restoration have an impact on the variability of land cover changes. On the one hand, the GFGP encourages vegetation restoration (increase in grassland areas), and on the other hand, climatic variability (wind speed and rainfall) also significantly influences vegetation growth in dry and semi-arid regions.

Soil wind erosion is actively decreased through ecological restoration, even if the ecological restoration’s early phases had promising results (1981–2000). During the middle and late phases, certain places saw severe wind erosion (2000–2010). Unreasonable human activities, such as overgrazing, reclamation, and fast urbanization, may have negative repercussions that partially outweigh the positive ones. Between 2011 and 2019, the Loess Plateau’s wind erosion modulus dropped (Figure 5 and Figure 6). This alteration can be ascribed to the ecosystems’ better soil protection capabilities as a result of restored plant cover. The outcomes revealed the great success of the GFGP in preventing soil wind erosion on the Loess Plateau.

4.3. Sustainable Management

Ecological restoration has helped regional and phased growth during the past 70 years, but owing to a lack of classification and divisional supervision, it has fallen well short of the strategic aim of ecological sustainability [42]. Water availability is the greatest barrier to maintaining plant growth and thus preventing soil erosion in dry and semi-arid regions. According to some studies, if the vegetation cover is too dense, the socio-economic costs can be prohibitive, but if the vegetation coverage is too thin, vegetation has little effect on controlling soil erosion and vegetation coverage should be at least 10%, or higher [1]. However, it is inappropriate at this time to suggest that excessive vegetation coverage should be increased to 40% in order to prevent wind erosion. Studies have also shown that the Loess Plateau’s low precipitation will prevent the long-term establishment of significant areas of vegetation if human influence is eliminated [43]. As a result, while developing methods to improve the efficacy of afforestation and reforestation operations, the constraint effects of water conditions on plant cover must be taken into consideration. Our research offers crucial justification for ecological restoration at the local and regional levels. The best vegetation cover, however, differs from location to location; therefore, it must be decided locally by taking into account the terrain, plant species, and their spatial distribution.

In conclusion, there may be serious environmental problems on the Loess Plateau in the twenty-first century because there is still an underlying contradiction between a vulnerable environment exposed to deterioration due to urbanization and dense population growth [39]. On the one hand, economic growth has to pick up speed in order to improve the area’s standard of living. To fix the delicate ecology, it is vital to consider the ecological balance. The evolution of society requires a stable economic environment. A balanced vegetation and sufficient water supplies are necessary for the growth of industry and agriculture. Determining how to balance environmental protection and economic expansion is essential. If there is a choice between ecological and economic benefits, ecological benefits should take priority since, in the current economic climate in China, only a robust ecosystem can accomplish long-term and sustainable economic development.

5. Conclusions

Based on an evaluation of the wind erosion on the Loess Plateau from 1981 to 2019, the RWEQ model found the regional patterns and temporal variations in soil wind erosion. Finally, the implications of the constraint effect in the control of soil erosion were examined after looking at the underlying causes and influencing variables of soil erosion. The key conclusions are stated below.

The plant cover on the Loess Plateau progressively rose between 1981 and 2019 when the “Grain for Green Program” that aimed to restore farmland to woodland or grassland was implemented, thus enhancing the ecosystem function of sandstorm avoidance. The wind erosion modulus decreased as a result of better plant coverage and climatic changes (e.g., decreased wind velocity). In other words, the same wind speed would result in less soil loss. These results showed that converting farmland back into woodland and grassland significantly improved the ecosystem service of controlling soil erosion.

In regions with extensive soil loss, significant work is still needed to promote plant regrowth. In the gully regions, it is also essential to build proper geotechnical structures and biological barriers. To maintain the long-term sustainability of the Loess Plateau’s Grain to Green Program, other initiatives, such as industrial transfer and rural development, should be created to offer farmers with lost acreage new means of subsistence. To promote long-term research and well-informed decision making in the area, a comprehensive monitoring program should be implemented to evaluate the impact of vegetation restoration efforts on the Loess Plateau. Finally, in order to strengthen ecological protection through Yellow River diversions, such as the ecological diversion to the Kubuqi Desert where severe wind erosion occurs, it is important to ensure the implementation of a Water–Sediment Regulation Scheme on the lower sections of the Yellow River. It is crucial to take regional economic development and environmental preservation into account in order to promote high-quality development on the Loess Plateau.