The impacts of China’s Shan-Shui Initiative on ecosystem services: a case study in the Three Gorges Reservoir Area

基于GIS的三峡库区生态风险评估及生态分区构建

Land use planning usually increases the uncertainties of the ecosystem structures and functions because various human demands usually bring both positive and negative ecological effects. It is critical for estimating various land use changes and their ecological effects, but the previous studies have failed to decouple the respective and the combined effects of different land use changes on ecosystem services. Net primary productivity (NPP) could be used to indicate many ecosystem services such as carbon sequestration and storage. Here, we employed a light use efficiency model to estimate the spatial and temporal dynamics of NPP in the Three Gorges Reservoir (TGR) area from 2000 to 2015, and designed four scenarios to analyze the relative roles of afforestation, urbanization and storing water on NPP dynamics. Our results documented that terrestrial NPP of the TGR area increased from 547.40 gC•m−2 to 629.96 gC•m−2, and carbon sequestration capacities were 31.66 TgC (1Tg = 1012g) and 36.79 TgC in 2000 and 2015, respectively. Climate change and land use change both could contribute to carbon sequestration with 4.08 TgC and 1.05 TgC. Among these land use changes, only afforestation could sequester carbon with 2.04 TgC, while urbanization-induced and impoundment-induced emissions were 0.12 TgC and 0.32 TgC, respectively, and other land use changes also could release 0.55 TgC of carbon. This finding suggested that although positive and negative environmental effects happened simultaneously over the past decades, green infrastructure could effectively offset the carbon emissions from urbanization and storing water in the TGR area, which provides some fundamental supports for further ecological restoration and contributes to empowering land use policies towards carbon sequestration and storage at the regional scale.

The transition of land use function and its effects on ecosystem services is a key issue in eco-environmental protection and is the basis of territorial space governance and optimization. Previous studies have typically selected land use types to evaluate ecosystem service value (ESV) and have overlooked comprehensive characteristics of ecosystem services and the mutual feedback relationship between human social systems and the ecosystem. Taking the Three Gorges Reservoir Area, Hubei section (TGRA-HS) as a case study, we used a transition matrix, the revised ESV method, and an ecological contribution rate model to explore land use function transition (LUFT) and its effects on the change in ESV based on the production–living–ecological space (PLES) classification system. The results show that: (1) The transition of land use function based on PLES was the mapping of the evolution of the human–nature relationship in the spatial pattern, which reflected the evolution of the spatial pattern caused by human interference with the continuous development of society; (2) The evolution of PLES showed the characteristics of a reduction in production space (P-space), and an expansion in living space (L-space) and ecological space (E-space). The distribution pattern of PLES from 1990 to 2020 was basically the same, and the characteristics of structural transform reflected the characteristics of project construction in different phases; (3) The E-space contributed the most to the total ESV, and it has risen by CNY 13.06 × 108. The transition of land use function caused by human construction projects impacts the spatiotemporal change in the regional ESV; (4) The change in ESV induced by LUFT revealed the whole dynamic process of the positive and negative effects of human construction projects on ecosystem services, and the two effects offset each other to keep the ESV relatively stable. The transition of E-space to P-space had the greatest impact on the reduction in ESV, whose contribution rate was 82.76%. The dynamic changes in land use function and ESV corresponding to the different stages of the Three Gorges Project’s (TGP) construction reveals the important driving effect of human activities on ecosystem services. It reminds us that humans should not forget to protect the eco-environment when obtaining services from the ecosystem.

Identifying and analyzing ecosystem service bundles and their socioecological drivers in the Three Gorges Reservoir Area

Land use/Land cover (LULC) changes as a result of policy planning influence ecosystem structures, processes, and functions, which are the basis for providing a wide range of ecosystem services (ES). There is an increasing consensus about the importance of integrating ES into ecological policy but quantifying the potential impacts of different policy on ES has proven difficult. We designed a remote sensing, geographic information system and scenario analysis-based approach to estimate and analyze the relationship between ES (soil conservation and carbon sequestration) and ecological policy designed to improve human welfare in the Chongqing municipality in the upper reaches of the Three Gorges Reservoir Area, China; a densely populated, highly modified watershed with serious soil erosion and flood hazard. Three alternative scenarios in 2050 were modeled for the Three Gorges Reservoir Area watershed. The model GEOMOD was used to predict future LULC changes due to policy planning. The ES models (Universal Soil Loss Equation model and Carnegie-Ames-Stanford Approach model) were designed to inform decisions, with an aim to align economic forces with conservation. We examine policy effectiveness by comparing scenarios for 2050 (Scenario1: Maintain current policy with no considerations of ES; Scenario2: Integrate ES into policy planning; Scenario3: Integrate ES into policy planning in view of the need of local people). Scenario-based LULC change analysis revealed that if the current afforestation policy continues (scenario 1), total ES would be further increased in 2050 due to expansion of forest cover. However, by targeting policy to improve ES provision (scenarios 2 and 3), ecological risks of soil loss can be significantly reduced and carbon sequestration enhanced. Scenario 3, thus, provided the best future environmental development scenario considering the need of local people in each region for ES. This scenario will theoretically help the Three Gorges Dam to harvest more ecological benefits through improvements in soil conservation and carbon sequestration. This study highlights the observation that including ES in policy planning and has a great potential to generate opportunities to maximize ES. This study highlights that including ES in policy planning has a great potential to generate opportunities to maximize ES. Hence, there is a need to encourage proper implementation of ecological policy to maintain and improve ES.

Land use/land cover (LULC) changes impact the structure and functioning of ecosystems, which consequently influences the provisioning of a range of ecosystem services (ES). There is a growing consensus regarding the merit of integrating the evaluation of ES into regional policy planning. The Yangtze River is the world's third longest and supports more than 6% of its population. However, assessing the potential impacts of different resource management policies upon ES is complicated in the Yangtze basin. To remedy this, here we designed a scenario analysis-based approach that used remotely sensed data and GIS (geographic information system) to analyze the relationships between ES (i.e., water flow regulation, water purification) and policies envisioned to improve human welfare in the Chongqing municipality, in the upper reaches of the Three Gorges Reservoir Area (TGRA) in the Yangtze basin. This watershed area has high population density and suffers from severe flood hazard and critical pollution issues. The GEOMOD modeling technique was used to predict LULC changes according to policy planning alternatives, producing scenarios by 2050 for the TGRA watershed. The GIS-based ES model (InVEST model) was developed as a tool to inform the decision-making process with the intention of aligning conservation measures with economic development. We examine policy effectiveness by comparing three scenarios for 2050: scenario-1 maintains the current policy, with no considerations of ES; scenario-2 integrates ES into policy planning; and scenario-3 integrates ES into policy planning considering the needs of local people. Our scenario-based LULC change analysis showed thatthe land with large increases in water flow regulation (i.e., values ≤-3000 × 103 m3 km-2) were scattered over the entire study area, while phosphorus reduction (i.e., values ≤ -30 kg km-2) were located mainly along rivers in all scenarios. Scenario-2 and scenario-3 are based on policies aiming at enhancing ES provisioning; for these, the projected ecological risks of water pollution are significantly reduced (39.97% and 37.58%, respectively). Total net changes of the investigated ES under scenario-2 or scenario-3 were almost double that occurring under scenario-1. Although scenario-2 and scenario-3 showed a near-equal total net change, water purification under scenario-2 was the greatest relative to forest expansion. However, scenario-3 offered the best future environmental development scenario, as it accounted for the demand and supply characteristics of water yield and purification in different regions. The water purification service made the greatest contribution to positive and negative effects (26%-47% and -7%, respectively) on ES provisioning. Linking water purification service to policy planning would effectively improve the overall ES. These scenario forecasting results will help the Three Gorges Dam to gain more ecological benefits via improvements to water flow regulation and the effective alleviation of degraded water quality in heavily populated regions in the Yangtze basin.

Regional Properties of Landslides.- Geo-hazard Initiation and Assessment in the Three Gorges Reservoir.- Bank Slope Stability Evaluation for the Purpose of Three Gorges Reservoir Dam Construction*.- Research on the Characteristics and Slope Deformation Regularity of the Badong Formation in the Three Gorges Reservoir Area.- Distribution of Dangerous Rockmasses on the High Steep Slopes in the Three Gorges Area.- An Evaluation Study of Bank Collapse Prediction in the Three Gorges Reservoir Area.- Distribution Features of Landslides in Three Gorges Area and the Contribution of Basic Factors.- Discussion on Land Use Based on Landslide Management in Three Gorges Reservoir Areas.- Case Studies for Typical Landslides.- Mechanism for the Rapid Motion of the Reactivated Qianjiangping Landslide in Three Gorges Dam Reservoir, China.- Evaluation of the Roles of Reservoir Impoundment and Rainfall for the Qianjiangping Landslide in Zigui County, Three Gorges Area.- Unsaturated Creep Test and Modeling of Soils from the Sliding Zone of the Qianjiangping Landslide in the Three Gorges Area, China.- Monitoring on Shuping Landslide in the Three Gorges Dam Reservoir, China.- The Anlesi Landslide in Wanzhou, China: Characteristics and Mechanism of a Gentle Dip Landslide.- Preliminary Study on Mud-Rock Flows Channel of the Bailuxi River, Wuxi County, China.- Stability Assessment and Stabilizing Approaches for the Majiagou Landslide, Undergoing the Effects of Water Level Fluctuation in the Three Gorges Reservoir Area.- Mass Rock Creep and Landsliding on the Huangtupo Slope in the Reservoir Area of the Three Gorges Project, Yangtze River, China.- Study on the Possible Failure Mode and Mechanism of the Xietan Landslide When Exposed to Water Level Fluctuation.- A Study of the 1985 Xintan Landslide in Xiling Gorge, Three Gorges Area, China.- Time Prediction of the Xintan Landslide in Xiling Gorge, the Yangtze River.- Back-Analysis of Water Waves Generated by the Xintan Landslide.- New Methodologies Applied in this Area.- Intelligent Optimization of Reinforcement Design Using Evolutionary Artificial Neural Network for the Muzishu Landslide Based on GIS.- The Application of Fractal Dimensions of Landslide Boundary Trace for Evaluation of Slope Instability.- Uncertainty Evaluation of the Stability of the Huanglashi Landslide in the Three Gorges of the Yangtze River.- Recognition of Lithology and Its Use in Identification of Landslide-Prone Areas Using Remote Sensing Data.- Construction and Application of a Real-Time Monitoring System for Landslides.- Entropy-Based Hazard Degree Assessment for Typical Landslides in the Three Gorges Area, China.- The Conceptual Model of Groundwater Systems in a Large-Scale Landslide - A Case Study of the Baota Landslide in the Impoundment Area of Three Gorges Project.- Bank Collapse Along the Three Gorges Reservoir and the Application of Time-Dependent Modeling.

Multiscale perspective research on the evolution characteristics of the ecosystem services supply-demand relationship in the chongqing section of the three gorges reservoir area

Constructing ecological security patterns (ESPs) is an important approach to maintaining regional ecological security and achieving sustainable development. Most previous studies on ESPs mainly focused on the supply of ecosystem services (ESs) yet did not fully consider the ecosystem health and human demand for ESs, which lacked evaluation from the perspective of human nature. Therefore, based on ecosystem health and ESs demand, this paper constructed the "vigor, organization, resilience, ESs supply-demand ratio" (VORSD) ecosystem health evaluation system and combined it with circuit theory to develop a new and comprehensive ESPs identification framework. Taking the Three Gorges Reservoir Area in Chongqing section (TGRAC) as a case study, the results showed that the general ecosystem health of the TGRAC was not optimistic, and there was still a long way to go for ecological treatment and restoration. From the perspective of spatial distribution, there were significant differences in the ecosystem health between regions, and the eastern region was higher than the western region. The ecological sources area of the TGRAC was about 25,350.16 km2, mainly distributed in the northeast and southeast of forestland, grassland, and cultivated land. The total length of ecological corridors was 2291.41 km, linking the northeastern, southeastern, middle, and southwestern regions of the TGRAC. There were 82 ecological nodes and 30 ecological barriers, most of which were concentrated on the construction land and cultivated land in the southwest and should be regarded as priority areas for ecological conservation. The research results verify the regional suitability and rationality of integrating the VORSD model and circuit theory to construct ESPs, which can provide an important reference for regional ecological protection and land use pattern optimization.

In order to establish an effective early warning system for landslide disasters, accurate landslide displacement prediction is the core. In this paper, a typical step-wise-characterized landslide (Caojiatuo landslide) in the Three Gorges Reservoir (TGR) area is selected, and a displacement prediction model of Extreme Learning Machine with Gray Wolf Optimization (GWO-ELM model) is proposed. By analyzing the monitoring data of landslide displacement, the time series of landslide displacement is decomposed into trend displacement and periodic displacement by using the moving average method. First, the trend displacement is fitted by the cubic polynomial with a robust weighted least square method. Then, combining with the internal evolution rule and the external influencing factors, it is concluded that the main external trigger factors of the periodic displacement are the changes of precipitation and water level in the reservoir area. Gray relational degree (GRG) analysis method is used to screen out the main influencing factors of landslide periodic displacement. With these factors as input items, the GWO-ELM model is used to predict the periodic displacement of the landslide. The outcomes are compared with the nonoptimized ELM model. The results show that, combined with the advantages of the GWO algorithm, such as few adjusting parameters and strong global search ability, the GWO-ELM model can effectively learn the change characteristics of data and has a better and relatively stable prediction accuracy.

As a hot issue, the precipitation characteristics of the Three Gorges Reservoir (TGR) area drew widespread interest from domestic and overseas academic circles. Based on China's surface-based meteorological monthly precipitation data from 1961 to 2016 in the TGR area, the spatial, inter-annual and inter-decadal, and multi-time-scale changes of precipitation in the TGR area are analyzed by using Collaborative Kriging (Co-Kriging, CK) Interpolation, linear regression analysis, Morlet wavelet analysis and 5-year sliding average processing, which provide the reference basis for further discussion on the impact of climate change, flood control and drought relief work in the reservoir area. Research shows that in the past 56 years, the average annual precipitation in most areas of the TGR ranges from 1,000 to 1,200 mm; the variation of precipitation in the TGR area shows a weak decreasing trend, with great fluctuation between year and generation, and the precipitation in each decade has a ‘less-more-less’ changing trend; the annual precipitation in the TGR area has periodic changes on multi-time scales, mainly including 25, 16 and 8 years. The smaller the scale the shorter the average period of precipitation change.

Influences of the alternation of wet-dry periods on the variability of chromophoric dissolved organic matter in the water level fluctuation zone of the Three Gorges Reservoir area, China

Landscape dynamics facilitated non-point source pollution control and regional water security of the Three Gorges Reservoir area, China

The Three Gorges Dam project and other human activities, including regional urbanization and industrialization, have had a substantial influence on the biological environment of the Three Gorges Reservoir Area (TGRA). They have changed the surface land use pattern, disrupted ecosystem structure and function, and influenced changes in the value of ecosystem services. The human activity intensity (HAI) assessment model, the ecosystem services value (ESV) assessment model, and the bivariate spatial autocorrelation model were used based on the spatiotemporal evolution data of towns along the Yangtze River in the TGRA in 1995, 2000, 2005, 2010, 2015, and 2020. At the same time, the spatiotemporal impact of the HAI on land use patterns was evaluated and the magnitude of the spatiotemporal influences on the ESV was investigated. The findings demonstrate the following: (1) The TGRA’s higher reaches are occupied by forested land, while the middle and lower portions are characterized by agricultural land. Land change in the reservoir region has mostly featured transitions between wooded land, agricultural land, grassland, and building land during the last 25 years. Because of differences in natural geography and administrative divisions, the intensity of human activity in the TGRA changes throughout the Yangtze River, with higher intensity in Chongqing and lower intensity in Hubei. By comparing the ESV and the HAI and validating with Moran scatter plots, it was determined that there is a negative relationship between the value of ecosystem services and the intensity of human activities. (2) The ESV rose from CNY 1017.16 × 108 in 1995 to CNY 1052.73 × 108 in 2020, suggesting that the policies of converting farmland back into forests, eliminating outdated production capacity, and developing green industries, among other ecological conservation measures, are effective. (3) In the research area, the effect coefficient of HAI on ESV ranges from −0.02 to −0.032 to −0.031. This coefficient represents the correlation between the HAI and ESV and can preliminarily judge the change in the degree of correlation between the HAI and ESV. The increase in HAI leads to a decrease in the value of ecosystem services, and there is a clear negative spatial correlation between the two. The low human activity area and low ecosystem service value area in the Chongqing section have been transformed into a high ecosystem service value area through years of returning farmland to forest and ecological management measures for sustainable development.

Studies of land use/cover change (LUCC) and its impact on ecosystem service (ES) in monetary units can provide information that governments can use to identify where protection and restoration is economically most important. Translating ES in monetary units into decision making strongly depends on the availability of spatially explicit information on LUCC and ES. Yet such datasets are unavailable for the Three Gorges Reservoir Area (TGRA) despite its perceived soil conservation service value (SCSV). The availability of remote sensing-based datasets and advanced GIS techniques has enhanced the potential of spatially explicit ES mapping exercises. Here, we first explored LUCC in the TGRA for four time periods (1995–2000, 2000–2005, 2005–2010, and 2010–2015). Then, applying a value transfer method with an equivalent value factor spatialized using the normalized difference vegetation index (NDVI), we estimated the changes of monetary SCSV in response to LUCC in a spatially explicit way. Finally, the sensitivity of SCSV changes in response to LUCC was determined. Major findings: (i) Expansion of construction land and water bodies and contraction of cropland characterized the LUCC in all periods. Their driving factors include the relocation of residents, construction of the Three Gorges Dam, urbanization, and the Grain for Green Program; (ii) The SCSV for TGRA was generally stable for 1995–2015, declining slightly (<1%), suggesting a sustainable human–environment relationship in the TGRA. The SCSV prevails in regions with elevations (slopes) of 400–1600 m (0°–10°); for Chongqing and its surrounding regions it decreased significantly during 1995–2015; (iii) SCSV’s sensitivity index was 1.04, 0.53, 0.92, and 1.25 in the four periods, respectively, which is generally low. Chongqing and its surrounding regions, with their pervasive urbanization and dense populations, had the highest sensitivity. For 1995–2015, 70.63% of the study area underwent increases in this sensitivity index. Our results provide crucial information for policymaking concerning ecological conservation and compensation.