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Soil erosion threatens environmental sustainability worldwide. Exploring the trajectories of soil erosion and associated drivers is of great significance for combating land degradation. This study selected the highly eroded Loess Plateau (LP) and Karst Plateau (KP) as contrasting regions to monitor soil erosion dynamics. Monitoring was performed by applying the Revised Universal Soil Loss Equation based on a GIS platform and multi-source input data to investigate associated drivers. The results established that soil erosion in both regions was substantially reduced by ecological restoration projects and significant land use/cover conversions. Landscape and geomorphological variables were found to be the dominant factors controlling soil erosion in the LP and KP, as they influenced land use patches and geomorphological patterns, respectively. The correlations between fragmentation metric indices and soil erosion indicated that the appropriately intensive fragmentation in the LP could mitigate or prevent soil erosion by disturbing its formation and transportation and ultimately positively influenced soil erosion control. Geomorphological patterns were also determinative factors, particularly for the KP, where almost all geomorphological variables were significantly correlated with the erosion modulus. Owing to the peculiar landform and landscape conditions in karst areas and loess hilly-gully areas, geomorphological and landscape variables should be considered when determining the main factors affecting soil erosion processes and integrated into the forecasting model to improve the accuracy of the simulation. The findings of this study are expected to (i) improve the efficacy of soil erosion control and (ii) promote the sustainable planning and management of land and soil resources.

Land degradation is one of the most serious environmental challenges that profoundly affects ecosystem services (ESs), which further threaten ecosystem sustainability. However, few studies have been committed to sufficiently explore the relationship between land degradation neutrality (LDN) and the ES balance of supply and demand sides, as well as their spatial disparities and determinants. To fill the knowledge gaps, this study quantifies land dynamics and ES balance through biophysical models and an expert knowledge matrix, respectively, and explores the spatial determinants through an integrated regression method. From 1990 to 2018, the ecosystem restoration projects in the Loess Plateau substantially reduced soil loss and maintained ES surplus patterns for the entire regional scale, except for individual urban agglomerations, which suffered from ES deficits. Spatial panel models and geographically and temporally weighted regression revealed that the ES balance and soil loss were concurrently determined by socioeconomic indicators, landscape composition, and structure. In addition, the spatial determinants presented remarkable regional heterogeneities and spillover effects depending on individual environmental and socioeconomic conditions, which should be taken into account in landscape monitoring, simulation, forecasting, and planning. Therefore, ecosystem restoration and landscape management should not solely depend on individual indicators in local units, but also rely on integrated frameworks and coordinated collaborations from cross-border areas that appropriately link LDN and ES balance maintenance targets by considering common critical determinants and their external effects. This study enriches the understanding of ecosystem evolution and sustaining ES balance. The findings are expected to further support policy formulations and implementations to address land degradation challenges and enhance ecosystem sustainability. [ABSTRACT FROM AUTHOR]

Ecological restoration efforts to combat soil loss often fail to deliver the expected benefits despite enormous investments. Better understanding the close relationships between climate, vegetation, and non-linear ecosystem dynamics can help restoration activities meet their intended goals. The severely eroded Loess Plateau (LP) was selected for a case study to investigate the underlying drivers of soil retention change and their non-linear constraint impacts. The soil retention function was substantially enhanced during 2000–2015, while the water yield function was weakened. Both the favourable changes in climate conditions (i.e., increasing precipitation and declining evapotranspiration) and governmental policies for soil and water conservation and ecological restoration promoted vegetation restoration and expansion, thereby strengthening the soil retention function. Consequently, water and sediment yields declined significantly. The relationship between water yield and soil retention is non-linear and shows that the two ecosystem functions can be either in synergy or in trade-off according to the level of vegetation cover. We observed that the vegetation cover had an upper threshold (i.e., 50%) for controlling the soil erosion because of the limited water condition (rainfall), which implies that the effect of vegetation on reducing the water erosion reached its maximum capacity when the plant cover was 50%. Considering the limited water conditions in drylands, to minimize the trade-off between the water yield and soil retention and to maximize the effectiveness of ecological restoration programs, it is recommended that the overall vegetation cover in the LP be controlled at approximately 30–40%, i.e., without exceeding 50%. Currently, the non-linear constraint effects of the water condition and vegetation cover on the soil retention are yet to be thoroughly understood. Moreover, practical policy recommendations require further field-based observations and experimental studies. • The soil retention function change during 2000–2015 was assessed. • The non-linear boundary of limited water resources was investigated. • The ecological restoration strategies in degraded drylands were discussed. [ABSTRACT FROM AUTHOR]

Highlights • We quantified the soil erosion change in a spatially explicit manner. • We investigated the driving forces of soil erosion change. • The hydrological effects of soil and water conservation were assessed. • The limitations and sustainability of soil and water conservation were discussed. Abstract Land degradation is a global environmental problem that threatens human safety and socioeconomic development. In order to alleviate severe soil erosion, China has implemented historically unprecedented large-scale afforestation. In this study, we selected the most severely eroded Loess Plateau as a case, to assess the effectiveness of soil and water conservation (SWC) efforts based on the Revised Universal Soil Loss Equation. In addition, the underlying drivers for soil erosion changes and hydrological effects of SWC were investigated, and finally the potential policy implications of our findings were discussed. The soil erosion intensity from 2000 to 2015 was weakened largely due to favorable climate conditions and SWC efforts, which promoted vegetation restoration and enhanced soil retention. However, there was a significant trade-off between water provision and soil retention functions. The excessively artificial afforestation reduced sediment yield but depleted surface runoff. Furthermore, artificial afforestation and increasing irrigation water consumption overused groundwater resources and finally lowered groundwater table. The SWC efforts characterized by artificial afforestation induced soil moisture declining, particularly for the conversion type of farmland to forest/shrub. Our results suggested that afforestation might be a poor choice in arid and semiarid regions, because it did not consider local precipitation conditions, and have exacerbated water shortages and offset SWC efforts. Therefore, the future ecological restoration efforts should be transformed from simple species-based measures to optimal plant species combinations to minimize the tradeoff between water yield and soil retention. The strategies for ecological restoration of drylands should also account for water balance to ensure effectiveness and sustainability. [ABSTRACT FROM AUTHOR]

Highlights • Wind erosion status was assessed in the most seriously eroded area of China. • The constraint effects among climate, vegetation, and soil erosion were revealed. • The underlying drivers for wind erosion were investigated. • The implications of constraint effects on land degradation control were discussed. Abstract Soil erosion is a widespread environmental problem, which threatens the environmental sustainability. The northwest arid region (NAR) in China is known as one of the most severe soil loss in the world that suffering from wind erosion. Based on the Revised Wind Erosion Equation (RWEQ), the spatio-temporal change of wind erosion was identified, and the underlying drivers and influencing factors of soil erosion process were investigated. In addition, the implications of constraint effects in soil erosion control were discussed. The results showed that the wind erosion from 1990 to 2013 was substantially lessened, and the government-aided desertification prevention and control programs, as well as increasing precipitation and decreasing wind speed might have contributed to these trends. The constraint line analyses indicated that the vegetation cover had nonlinear and threshold effects on soil erosion through constraining the water condition (precipitation). Specifically, when the precipitation is below the threshold (approximately 50–100 mm yr−1 in the NAR), the precipitation (water condition) is not sufficient to maintain a good vegetation cover (about 20–40%), therefore the vegetation cannot efficiently prevent wind erosion. However, once the precipitation exceeds this threshold, the vegetation's sand retention function will enhance and thereby reducing soil loss substantially. Vegetation cover has a lower and an upper threshold for controlling wind erosion. A plant cover lower than 10% does little to reduce wind velocity at the soil surface. The effect of vegetation on reducing wind erosion basically reaches the maximum when plant cover is 40% or above. The constraint effects of precipitation on vegetation cover in the arid region should be considered to improve the efficiency of afforestation and reforestation efforts aiming at mitigating and preventing soil loss. [ABSTRACT FROM AUTHOR]

Abstract Soil erosion is a widespread environmental problem that threatens environmental sustainability. The Loess Plateau (LP) in China is one of the most severely eroded areas in the world. In this study, the soil erosion dynamics were assessed by applying the Revised Universal Soil Loss Equation and the Revised Wind Erosion Equation; further, the underlying drivers for soil erosion processes were investigated. In addition, implications of constraint effects in soil erosion control were discussed. The results showed that there was a substantial reduction in both wind and water erosion between 2000 and 2015; it is considered that vegetation restoration (mainly in relation to government-aided ecological restoration programs), increased precipitation, and a decrease in wind speed may have contributed to these trends. Land cover and soil properties contribute to spatial patterns of soil erosion. Thus, ecological restoration programs have promoted improvements in soil properties, leading to an eventual reduction. Constraint line analysis indicates that vegetation cover has a nonlinear and threshold effect on soil erosion through constraining the water condition (i.e., rainfall). With respect to water erosion, when rainfall is below the threshold (approximately 450–500 mm), it is not sufficient to maintain a good vegetation cover (about 30–40%), and vegetation cannot efficiently prevent soil erosion; however, once rainfall exceeds the threshold, the soil retention function of the vegetation is enhanced and soil loss is substantially reduced. In addition, there is a lower (10%) and an upper (40%) threshold at which vegetation can control wind erosion, which implies that plant cover lower than 10% has a minimal effect on reducing the wind velocity at the soil surface, and the effect of vegetation on reducing wind erosion is at its maximum when plant cover is 40% or above. However, if human intervention is removed, the limited amount of rainfall on the LP would be insufficient to support large areas of trees in the long-term; therefore, the constraint effects of the water condition on vegetation cover need to be considered to improve the efficiency of afforestation and reforestation efforts aimed at mitigating and preventing soil loss. Highlights • We quantified the soil erosion change in a spatially explicit manner. • We investigated the driving forces of soil erosion change. • The constraint effect between wind erosion and vegetation cover was quantified. • The implications of constraint effect in soil erosion control were discussed. [ABSTRACT FROM AUTHOR]

The Loess Plateau (LP) is one of the most fragile eco-regions in China, and is characterized by severe soil erosion and water shortage. The fragile environment poses a threat to ecological safety and sustainable development on the LP and neighboring areas. The ecosystem on the LP has undergone great changes in recent decades owing to dramatic climate change, ecological rehabilitation, and tremendous human pressure. This study was focused on quantifying and assessing the multiple ecosystem services from 2000 to 2012, based on actual observation records and widely used biophysical models. These included Universal Soil Loss Equation (USLE), Revised Wind Erosion Equation (RWSQ), Carnegie-Ames-Stanford Approach (CASA), and rainfall storage method. Furthermore, in this study, the roles of climate variability and an ecological restoration program on vegetation activity and ecosystem services were investigated, as well as the synergies between multiple ecosystem services. The slight increase in both precipitation and temperature during 2000–2012, in conjunction with ecological rehabilitation, induced a trend of increasing in vegetation cover and productivity. During 2000–2012, the overall soil retention function was slightly enhanced while the amount of hydrological regulation decreased. The biomass production (vegetation carbon sequestration) and food production increased sharply. The increasing precipitation intensified water erosion by enhancing rainfall erosivity, whereas the reduction in wind speed lessened wind erosion and thereby reduced the frequency and duration of sandstorm events. Vegetation restoration supported by climate variability and resulting from ecological projects also played positive roles in soil retention enhancement. The spatial correlation analyses indicated synergies between multiple regulating ecosystem services. There was also a synergy between food production and carbon sequestration in vegetation. The performance of ecological rehabilitation and changes in ecosystem services on the LP exemplified the need for ecological conservation to take climate variability into account, and to facilitate synergies involving multiple ecosystem services, to maximize human well-being and preserve natural ecosystems. [ABSTRACT FROM AUTHOR]

Land degradation is a widespread environmental challenge that threatens landscape sustainability and regional development; existing land degradation neutrality (LDN) efforts in karst areas do not sufficiently consider the complex associations of soil loss with ecosystem services (ESs) and their spatial determinants, which constrain the efficacy of ecosystem restoration projects (ERPs). To close these gaps, this study conducted in China's southwest karst area explored the simultaneous responses of soil loss and ESs to human interventions and identified their spatial determinants by applying biophysical models and an integrated regression approach, respectively. The results showed that, from 1980 to 2017, ERPs substantially enhanced soil retention (SR) for both sub-catchment and entire region scales, and the soil loss has greatly declined since 1999. Carbon stock (CS) and habitat quality remained relatively stable over the entire region, while precipitation variations resulted in fluctuations in water yield (WY) and aquatic purification (AP). Pairwise correlations demonstrated that WY and AP had a significant synergy (p < 0.0001) across all provinces, while CS and WY presented a negative association for Guangxi and Guizhou provinces. Spatial panel models and geographically weighted regressions determined that environmental, socioeconomic, and landscape variables were the primary spatial determinants of multiple ESs and soil loss, and presented significant spatial heterogeneity and spillover effects. Therefore, SR and other ESs should be closely linked, to concurrently address land degradation and enhance ESs. In ERPs and LDN practices, environmental, socioeconomic, and landscape variables and their external effects should be taken into account to propose targeted, integrated, and efficient policies and strategies to facilitate win–win outcomes and realize regional sustainable development. [ABSTRACT FROM AUTHOR]

Land degradation neutrality (LDN) has been widely recognized as an important target to achieve goals for global sustainable development. Ecological restoration projects (ERPs) are considered a traditional approach to mitigate wind erosion by altering the structures and functions of the ecosystem. Thus, the efficiency of China's historical large-scale ERPs for wind erosion mitigation should be examined and optimized to better address this global environmental challenge. We assessed the change in wind erosion using a biophysical model and investigated the associated drivers identified. In addition, the efficiency of ERPs was examined by adopting the theory of non-linear ecosystem dynamics. The erosion modulus significantly declined from 1990 to 2017, but this declining trend reversed since 2009. The structural equation model and related analyses revealed that the declining wind speed, wetting soil moisture, and vegetation greening substantially reduced wind erosion, while the reversal of declining wind speed around 2009 aggravated wind erosion, particularly in the northern Inner Mongolia Sandstorm Area. The relatively arid climate restricted vegetation restoration and further offset afforestation efforts, resulting in the transition of declining erosion modulus. From the perspective of non-linear ecosystem dynamics, a wet climate provides a crucial window of opportunity for ERP in drylands, while the window of risks due to dry and windy climates may extend the time required for a shift change after ERP and may postpone the stage change toward the LDN goal. Hence, climate-induced windows of opportunity and risks are crucial in identifying the time for initiating ERPs, and existing environmental conditions and critical thresholds should be carefully considered. • The spatiotemporal change in wind erosion modulus was revealed. • The efficiency of ecological restoration programs was examined. • The underlying drivers of soil erosion were investigated. • The response of soil loss to afforestation efforts was discussed from non-linear ecosystem perspective. [ABSTRACT FROM AUTHOR]

Land degradation is one of the most serious environmental problems worldwide. To combat land degradation, China has implemented a series of ecological restoration programs (ERPs). This study selected the northern dryland of China as a case study to examine the efficiency of ERPs, and the response of soil loss to afforestation efforts and climatic conditions was discussed using the principles from the ecological theory of non-linear ecosystem dynamics. Owing to the combined impacts of declining wind speed and rapid vegetation restoration, the soil erosion for the entire region was substantially reduced from 1990 to 2015. However, the rainfall fluctuated considerably, particularly for the period from the late 1990s to early 2000s. Several drought events to some extent inhibited vegetation growth and further offset afforestation efforts, resulting in degradations in vegetation structure and soil retention function, which have been aggravating soil erosion since 2005. In certain representative sandstorm areas, limited increase in rainfall was not enough to promote vegetation growth, and therefore the vegetation cover did not present increasing trends and, in some cases, even declined significantly. The responses in terms of land degradation to climatic conditions and afforestation efforts behaved in a non-linear dynamic manner, providing essential insights into appropriate timings, climate-induced windows of opportunity, and risk in recovering and sustaining ecosystems, and eventually moving towards the land degradation neutrality (LDN) target. The climate-induced windows of opportunity and risk are critical in identifying the time for starting human interventions to mitigate and halt land degradation. Meanwhile, effective investment actions should be taken according to existing environmental conditions and critical thresholds, to achieve LDN at minimum risk and cost. Unlabelled Image • The spatiotemporal changes in soil loss and their ecological implications were revealed. • The efficiency of ecological restoration programs was examined. • The underlying drivers of soil erosion were investigated. • The response of soil loss to afforestation efforts was discussed from non-linear ecosystem perspective. [ABSTRACT FROM AUTHOR]

Topsoil erosion is a widespread and major threat to terrestrial ecosystems that leads to environmental deterioration. Monitoring soil erosion dynamics and understanding the driving mechanisms are of great significance for optimizing ecological restoration programs and combating land degradation. We apply a widely used soil erosion assessment model to quantify the changes in soil erosion on the Loess Plateau (LP) in response to afforestation-induced vegetation cover and land use/cover changes. Furthermore, we examine the relationship between landscape metrics and soil erosion using spatial econometric approach. The results indicate that soil erosion in the LP substantially decreased through afforestation efforts, while the observed sediment load declined significantly as a result of soil and water conservation programs. A number of largescale ecological programs altered the spatial configuration and structural composition of the landscape from different aspects, which disturbed the formation and transportation of soil erosion, eventually resulting in a reduction in soil loss. The spatial association between landscape metrics and soil erosion indicated that properly fragmented landscapes can effectively decrease soil erosion. Due to the spatial spillover, soil erosion in one county can be affected by soil erosion in adjacent counties. Therefore, the spillover effect between counties should not be ignored, and the responsibility for formulating and implementing solutions to combat land degradation should not fall solely on individual local governments. Preferably, the cooperation between different regions should be strengthened as a critical way to improve the efficiency of programs combating land degradation. • The landscape pattern metric changes were quantified. • The responses of soil loss to afforestation programs were revealed. • The associations between soil erosion and landscape metrics were investigated via spatial econometric approach. • The spatial spillover effects and their practical implications were discussed. [ABSTRACT FROM AUTHOR]

The Three-Rivers Headwater Region (TRHR) is the headwater of the Yangtze River Basin (YARB), Yellow River Basin (YRB), and Lancang River Basin (LRB); it is known as China's 'Water Tower' owing to its important supply of freshwater. In order to assess ecosystem changes in the TRHR during 2000–2012, we systematically and comprehensively evaluated a combination of model simulation results and actual observational data. The results showed the following: (1) Ecosystem pattern was relatively stable during 2000–2010, with a slight decrease in farmland and desert areas, and a slight increase in grassland and wetland/water-body areas. (2) A warmer and wetter climate, and ecological engineering, caused the vegetation cover and productivity to significantly improve. (3) Precipitation was the main controlling factor for streamflow. A significant increase in precipitation during 2000–2012 resulted in an obvious increase in annual and seasonal streamflow. Glacier melting also contributed to the streamflow increase. (4) The total amount of soil conservation increased slightly from 2000 to 2012. The increase in precipitation caused rainfall erosivity to increase, which enhanced the intensity of soil erosion. The decrease in wind speed decreased wind erosion and the frequency of sandstorms. (5) The overall habitat quality in the TRHR was stable between 2000 and 2010, and the spatial pattern exhibited obvious heterogeneity. In some counties that included nature reserves, habitat quality was slightly higher in 2010 than in 2000, which reflected the effectiveness of the ecological restoration. Overall, the aforementioned ecosystem changes are the combined results of ecological restoration and climate change, and they are likely a local and temporary improvement, rather than a comprehensive and fundamental change. Therefore, more investments and efforts are needed to preserve natural ecosystems. [ABSTRACT FROM AUTHOR]