Identifying ecological security patterns based on the supply, demand and sensitivity of ecosystem service: A case study in the Yellow River Basin, China

Spatiotemporal pattern and obstacle factors of coupling relationship between habitat quality and urbanization level in the Yellow River Basin, China

Land use change stands as the primary factor influencing habitat quality (HQ). Clarifying the spatiotemporal change and the obstacle factors of the coupling relationship between HQ and urbanization level (UL) can provide imperative references for achieving sustainability in the Yellow River Basin (YRB). This study is based on the InVEST model, spatial autocorrelation, and obstacle factor analysis to measure the spatiotemporal dynamics and impediments of the coupling relationship between HQ and UL from 2000 to 2020 in the YRB. The findings were as follows: (1) From 2000 to 2020, the HQ showed a tendency of rise first and then fall, with the pattern of "High in the middle and west, low in the east"; (2) from 2000 to 2020, the UL had an upward trend, with the pattern of "Low in the west, high in the middle and east"; (3) the coupling and coordination level of HQ and UL in the YRB changed from extreme incoordination to verge of coordination, and it had a distribution pattern of "High in the east, low in the west", with the high-value area expanding to the east and the low-value area shrinking to the west. (4) Location condition, climate, proportion of construction land, vegetation index, and proportion of non-agricultural employment are the main obstacle factors that determined the coupling and coordination of the HQ and UL.

Coupling eco-environmental quality and ecosystem services to delineate priority ecological reserves-A case study in the Yellow River Basin

Priority ecological reserves (PER) aim to protect areas with significant ecological value and crucial ecological functions, optimizing resource allocation to maximize the benefits of ecological conservation. However, most previous studies have considered only ecosystem services (ESs) in delineating PER, neglecting eco-environmental quality (EEQ). This study used the Remote Sensing-based Ecological Index (RSEI) to represent EEQ and combined it with ESs to delineate PER at the county scale in the Yellow River Basin (YRB). Additionally, it employed Multiscale Geographically Weighted Regression to identify the driving factors influencing the ESs and EEQ of PER. The results showed that: (1) From 2000 to 2020, both RSEI and the Comprehensive ESs (CES) in the YRB exhibited a fluctuating upward trend; (2) Three types of PER were extracted, with ESs reserve mainly distributed in the upstream region, EEQ reserve primarily in the middle and lower reaches, and integrated ecological reserve mainly in the midstream region, all dominated by vegetation land-use types; (3) Within the extracted PER, RSEI was mainly influenced by soil, aspect, population (pop), PM2.5, temperature (tmp), and potential evapotranspiration (pet), while CES was affected by soil, pop, PM2.5, slope, tmp, precipitation, and pet. To enhance the EEQ and ESs of the YRB, it was recommended to incorporate at least 105,379 km2 into the existing protected areas in the YRB. These areas should be subdivided based on their ecological status, with specific management measures for different types of PER. This study provides recommendations for environmental protection and land planning in the YRB, actively responding to current policies on high-quality development and ecological environmental protection in the YRB.

Optimizing zoning for ecological management in alpine region by combining ecosystem service supply and demand with ecosystem resilience

In order to enhance ecosystem stability and promote sustainable regional ecological, social, and economic development, it is crucial to explore the coupling relationship between ecosystem service supply and demand and the resilience of ecosystem, so as to propose scientific ecological management zones and strategies. Taking the vulnerable alpine ecosystem in Gannan Tibetan Autonomous Prefecture (Gannan Prefecture) as the study area, this paper comprehensively utilized multi-source data, grid analysis, ecosystem service supply and demand estimation model, and coupled coordination model to analyze the spatio-temporal differentiation and coordination pattern of ecosystem service supply and demand in the study area from 2000 to 2020. With the assistance of the Analytic Hierarchy Process (AHP), the ecosystem resilience index system was constructed to evaluate the regional ecological resilience. The results reveal the following: (1) In the past 20 years, the ecosystem service supply and resilience in Gannan Prefecture showed a fluctuating upward trend, and the demand continued to grow steadily. Their spatial differentiation were obvious, but the pattern remained stable. (2) There was a moderate incoordination indicated by the average coordination degree of the supply and demand coupling of ecosystem services, which rangeed between 0.3 and 0.4. (3) Gannan Prefecture was split into three ecological management zones, considering the spatial distribution of ecosystem service supply and demand, as well as resilience. Through system function monitoring and other measures, the ecological conservation zone will rely on its high resilience to support the restoration and self-sufficiency of the system, ensuring the stability and well-being of the ecosystem. The primary objectives of general protected zone includes environmental preservation, strict regulations, and the prevention of human intervention. To enhance their ecological background, key restoration zone must intensify the implementation of ecological restoration initiatives. To address the needs of the locals, strategies such as ecological compensation, optimizing the land use structure, and fostering the growth of environmentally friendly companies can be implemented simultaneously.

Construction of ecological security pattern in combination with landslide sensitivity: A case study of Yan'an City, China

The ecological security pattern can harmonize the relationship between natural environmental protection and socio-economic development. This study proposes a regional ecological security pattern optimization framework by integrating theory and practice with landslide sensitivity and landscape structure. Using Yan'an City as an example, this study optimizes the landscape layout of preliminary ecological sources. The landslide sensitivity index is generated using the information value model and then used to adjust the ecological resistance surface. The Minimum Cumulative Resistance (MCR) approach is used to extract ecological corridors, locate ecological nodes utilizing circuit theory, and outline crucial ecological control areas. The results demonstrate: (1) the ecological sources are primarily composed of forestlands, with a total area of 2,352.2400 km2, concentrated in the southwest, central, and southeast regions. The optimal landscape granularity for the source patches is 600 m. (2) Yan'an is divided into four landslide sensitivity level zones: extremely high, high, medium, and low, with the overall landslide sensitivity of the region being high. (3) The highest ecological resistance is observed in built-up land and the lowest in forestland. The total number of ecological corridors is 26, avoiding most of the highly sensitive areas of landslides. (4) The number of ecological pinch points is 61, while the ecological barrier points amounted to 54. The critical ecological control areas consist mainly of cropland, forestland, and grassland, and differentiated restoration strategies are proposed to address their unique characteristics. The findings of the research can offer scientific guidance for the practice of ecological security protection in geohazard-prone areas.

Stability in change: building a stable ecological security pattern in Northeast China under climate and land use changes

Climate change and land use change caused by human activities have a profound impact on ecological security. Simulating the spatio-temporal changes in ecosystem service value and ecological security patterns under different carbon emission scenarios in the future is of great significance for formulating sustainable development policies. This study quantified the four major ecosystem services (habitat quality, water retention, soil erosion, and carbon storage) in Northeast China (NC), identified ecological source areas, and constructed a stable ecological security pattern. The results show that the spatial patterns of soil erosion, carbon storage, water retention, and habitat quality, the four major ecosystem services in NC, are relatively stable in the next 30 years, and there is no significant difference from the current spatial pattern distribution. The SSP1-2.6 carbon emission scenario is a priority model for the development of NC in the next 30 years. In this carbon emission scenario, the NC has the largest ecological resources (191,177 km2) and the least comprehensive resistance value (850.006 × 10-4). At the same time, the relative resistance of the corridor in this scenario is the smallest, and the area of the mandatory reserve pinch points is the least. The ecological corridors in the SSP1-2.6 scenario form a network distribution among the ecological sources, connecting several large ecological sources as a whole. This study fills the knowledge gap in building a stable ecological security pattern in NC under the background of global change, and provides a scientific basis for the decision-making of regional ecological security and land resource management.

Optimizing the ecological network of resource-based cities to enhance the resilience of regional ecological networks

Mineral extraction in resource-based cities has caused serious damage to the original ecology, resulting in poor regional vegetation growth, reduced carbon sequestration capacity, and reduced ecosystem resilience. Especially in resource-based cities with fragile ecology, the overall anti-interference ability of the environment is relatively worse. Seeking ecological network optimization solutions that can improve vegetation growth conditions on a large scale is an effective way to enhance the resilience of regional ecosystems. This paper introduces carbon sequestration indicators and designs a differential ecological networks (ENs) optimization model (FTCC model) to achieve the goal of improving ecosystem resilience. The model identifies the patches that need to be optimized and their optimization directions based on the differences in ecological function-topology-connectivity-carbon sequestration of the patches. Finally, the resilience of the ecological network before and after optimization was compared, proving that the model is effective. The results show that the sources in the Yulin ENs form three main clusters, with connectivity between clusters relying on only a few patches. The patches in the northeastern and southwest clusters are large but their ecological functions need to be improved. After optimization, 16 new stepping stones were added, 38 new corridors were added, and the ecological function of 39 patches was enhanced. The optimized ecological network resilience was improved in terms of structure, function, and carbon sinks, and carbon sinks increased by 6364.5 tons. This study provides a reference for measures to optimize landscape space and manage ecosystem resilience enhancement in resource-based cities.

Ecological security warning in Central Asia: Integrating ecosystem services protection under SSPs-RCPs scenarios

Ecological security patterns (ESPs) are designed to enhance ecosystem structure and functionality while preserving vital ecosystem services (ESs). This study not only integrated the ES trade-offs related to ecological security warning, but also considered the effects of future climate changes and human activities on ESPs. By combining the revised universal soil loss equation (RUSLE), the revised wind erosion equation (RWEQ), the dry sedimentation (DS) model, the recreation opportunity map (ROM) and the integrated valuation of ESs and trade-offs (InVEST) model, this study projected provisioning services, regulation services and cultural services in Central Asia (CA) for historical periods (1995-2014) and future scenarios (2021-2099). An ecological security early-warning (source - corridor - barriers) framework was constructed based on the protection of ESs under the SSP126, SSP245 and SSP585 scenarios. The ordered weighted averaging method (OWA) was applied to this framework to identify ecological sources. The Minimum cumulative resistance model (MCR) and circuit theory were used to construct ecological corridors and barriers. Our results revealed that ES hotspot areas will decrease by 11.75 % to 16.42 % in CA under the SSP126, SSP245, and SSP585 scenarios. Under the ecological warning framework, the ecological source warning area will reach 792 km2-1942 km2 and 6591 km2-17,465 km2 under the SSP126 and SSP585 scenarios, respectively. In particular, in the 2050s under the SSP245 scenario, the number of key ecological corridor warnings will exceed 50 % of the total number of corridors. We found that ecological barrier warnings will mainly be distributed in desert areas with low vegetation coverage in southwestern CA. Building upon the reorganization of ESs within the ESP framework, we propose an ecological early warning strategy referred to as "one axis, two belts, two cores, and three zones". This novel approach aims to enhance our ability to predict and respond to ecological threats and challenges.

Incorporating network topology and ecosystem services into the optimization of ecological network: A case study of the Yellow River Basin

Human activity-induced landscape fragmentation seriously affects regional connectivity and biodiversity and hinders human well-being and sustainable development. These effects can be mitigated by the construction of ecological networks (ENs), but building extensive ENs requires cross-regional planning and coordination. Since ecosystems in different regions provide varying benefits to humans, optimizing ENs based on the quality of ecosystem services (ESs) is an effective way to rapidly improve regional landscape connectivity. In this study, we constructed an EN in the Yellow River Basin (YRB) according to landscape ecology and complex network theory, examined the network topology, measured three ESs using the InVEST model, and optimized the EN based on the coupling of EN topology and ES quality. In the YRB, the biodiversity index and carbon storage capacity were relatively higher and invariable. However, the wind-breaking and sand-fixing index was poorer, but it increased by 146 % during the study period. The number of ecological patches was roughly 48, accounting for about 40 % of the YRB region. From 1995 to 2020, the average ecological resistance decreased by 29 %, and the average number of corridors was 99, but the average corridor length first increased and then decreased. The number and area of ecological pinch points and barriers changed significantly. The EN topology strongly correlated with biodiversity and wind-breaking and sand-fixing, but not with carbon storage. In the face of random attacks, the optimized EN demonstrated significantly greater connectivity robustness. Under deliberate attacks, it exhibited better resilience and buffering power when the percentage of attacking nodes is in the 30 %-80 % range. For the ecological patches within a certain range of the attacking node, appropriate development and planning can be carried out in the future, while for the patches outside the range, strict ecological protection measures need to be implemented. This study provides theoretical references for improving EN planning efficiency and promoting synergistic cooperation in the YRB.

A study on matching supply and demand of ecosystem services in the Hexi region of China based on multi-source data

To achieve the best management of the ecosystem and sustainable socioeconomic development, it is crucial to clarify the matching relationship between the supply and demand of ecosystem services (ESs). Four types of ESs were chosen for the Hexi region in this study: food supply, carbon sequestration, water yield, wind erosion control and sediment retention. We assessed the supply-demand and matching relationships of different ESs using the Integrated Valuation of Ecosystem Service and Tradeoffs (InVEST) model, the ESs supply-demand ratio and the four-quadrant model. Moreover, we also analyzed the supply-demand ratio of integrated ESs and their cold spots. The findings suggest that (1) from 2000 to 2020, the average supply of food supply, carbon sequestration, water yield, wind erosion control and sediment retention increased by 44.31 t/km2, 128.44 t/hm2, 14,545.94 m3/km2 and 0.14 kg/m2 respectively, which showed a spatial pattern of "high in the southeast and low in the northwest". The average demand for food supply and carbon sequestration increased by 1.33 t/km2 and 0.32 t/hm2 respectively, while the average demand for water yield and wind erosion control and sediment retention decreased by 2997.25 m3/km2 and 1.19 kg/km2 respectively. The spatial distribution is consistent with the layout of population density, production and residential areas, and fragile ecological areas. (2) The supply-demand ratio of food supply, carbon sequestration and water yield is greater than 0.095, which is in a state of oversupply, and the supply-demand ratio of wind erosion control and sediment retention is less than 0, which is in a state of shortage; all ESs are mainly in low-low spatial matching areas, mainly concentrated in the desert areas of the northwest in the Hexi region. (3) The supply-demand ratio of integrated ESs increased by 0.024, and the proportion of cold spots and sub-cold spots was more than 50% and concentrated in the northwest, while hot spots and sub-hot spots accounted for only about 16%, mainly distributed in the southern Qilian Mountains and some oasis areas.

Identification of critical ecological areas using the ecosystem multifunctionality-stability-integrity framework: A case study in the Yellow River basin, China

Critical ecological areas (CEAs), as important regions for biodiversity and ecosystem functions, are crucial for ecological conservation and environmental management at regional and global scales. However, the methodology and framework of CEA identification have not been well established. In this study, a comprehensive CEA identification method was developed based on the ecosystem multifunctionality-stability-integrity framework by using K-means clustering, critical slowing down theory and possible connectivity. Taking the Yellow River basin (YRB) as a case study, our results showed that ecosystem multifunctionality gradually decreased from the southeast to northwest. A decrease in ecosystem stability was observed since 2017 and was mainly due to the increased impacts of human activities and urbanization within the 10-20 km distance threshold from the ecosystem. Based on the proposed framework, 15.13% of the YRB was identified as CEAs with reliable estimates, and most areas were distributed in the Three-River Headwaters, Qinling and Taihang Mountains. Moreover, urbanization and precipitation were found to be the dominant environmental factors affecting the CEA distribution in the YRB. Our results indicated that the proposed framework could provide a comprehensive approach for CEA identification and useful implications for ecological conservation and environmental management.

Relocating built-up land for biodiversity conservation in an uncertain future

Land use changes associated with habitat loss, fragmentation, and degradation exert profoundly detrimental impacts on biodiversity conservation. Urban development is one of the prevailing anthropogenic disturbances to wildlife habitat, because these developments are often considered permanent and irreversible. As a result, the potential benefits of built-up land relocation for biodiversity conservation have remained largely unexplored in environmental management practices. Here, we analyze recent built-up land relocation in Shanghai and explore how such restoration programs can affect future land change trajectories with regards to biodiversity conservation. Results show that 187.78 km2 built-up land in Shanghai was restored to natural habitat between 2017 and 2020. Further simulation analysis highlights that relocating built-up land can substantially promote conserve biodiversity. In particular, there would be less habitat loss, better natural habitat quality and more species habitat-suitable range under the scenarios with built-up land relocation. Species extinction assessment suggest that amphibians, mammals, and reptiles will all have an increasingly high extinction risk without built-up land relocation. However, there will even be a marginal decrease in extinction risk over time for mammals and reptiles if the relocation of built-up land is permitted, but still a moderate increase in extinction risk for amphibians. This study highlights the importance of incorporating rigorous conservation planning prior to development activities, thereby underpinning a sustainable approach to environmental management.

Linking ecosystem service flow to water-related ecological security pattern: A methodological approach applied to a coastal province of China

Water security is a critical concern due to intensifying anthropogenic activities and climate change. Delineating a water-related ecological security pattern can help to optimize spatial configuration, which in turn can inform sustainable water management. However, the methodology remains unclear. In this study, we developed a framework linking ecosystem service flow to water-related ecological security pattern; hence, we identified the sources, sinks, key corridors, and vulnerable nodes in Fujian Province, China. Our results revealed that the sources were located inland at high altitudes with a decreasing area trend in the south and an increasing area trend in the north, whereas the sinks were spread in coastal areas and exhibited a decreasing trend with relatively stable spatial distribution. The water-related ecological security has degraded as represented by a decreasing ecological supply-demand ratio over the last 30 years. Key corridors were identified in 17.12% of the rivers, and 22.5% of the vulnerable nodes were recognized as early warning nodes. Climate variability affected source distribution, while anthropogenic activities drove sink dynamics. These findings have important implications including landscape pattern planning and sustainable water management in the context of accelerated land use/cover and climate changes.

Spatial analysis enables priority selection in conservation practices for landscapes that need ecological security

Global urbanization has not only promoted social and economic development, but also contributed to seriously ecological challenges. As a type of sustainable landscape patterns, ecological security pattern is considered as an effective spatial pathway to simultaneously conserve ecological security and maintain social-economic development. However, the fragmentation issue of ecological sources of ecological security pattern has not been effectively addressed, although many case studies have been conducted to identify ecological security pattern. In this study, we used spatial conservation prioritization to identify the ecological security pattern of the city belt along the Yellow River in Ningxia, China. Ecological sources were selected using Zonation model while ecological corridors and key ecological nodes were identified with circuit model. The results showed that the ecological security pattern was composed of 97 ecological sources, 226 ecological corridors, 267 pinch points and 22 barriers, covering a total area of 7713.1 km2 and accounting for 34% of the study area. Ecological sources were concentrated in the Helan Mountain, Xiang Mountain and along the Yellow River. Besides, ecological corridors were dense in the southern and eastern part of the study area. Both indicated that the Yellow River and Helan Mountain were the conservation hotspots. Landscape connectivity of ecological sources identified through Zonation-based spatial conservation prioritization was better than that with the scoring approach based on ecosystem service importance. Particularly, in the Zonation approach the landscape connectivity increased with 44% while the average patch area increased with 28% when comparing with the scoring approach. The spatial conservation prioritization approach proposed in this study provides a new effective tool to construct ecological security pattern, which is conducive to the synergic enhancement of landscape connectivity and ecosystem services conservation.

Integrating Landscape Ecological Risks and Ecosystem Service Values into the Ecological Security Pattern Identification of Wuhan Urban Agglomeration

Urban agglomerations are the main form of China's future promotion of new urbanization development. Nevertheless, their accelerated expansion and development are increasingly threatening the security of regional ecosystems. The identification and optimization of ecological safety patterns (ESPs) is the fundamental spatial way to guarantee the ecological safety of urban circles and realize the sustainable development of the socio-economic and ecological environment. Nevertheless, from the perspective of urban green, low-carbon, and ecological restoration, regional safety evaluation still lacks a complete framework integrating ecological elements and social and natural indicators. Moreover, the evaluation method of ESPs also has a lack of judgment on the long-term change dynamics of regional landscape ecological risks and ecosystem service values. Thus, we proposed a new regional ecological security evaluation system based on ecosystem service value (ESV) and landscape ecological risk (LER), using the Wuhan urban agglomeration (WUA) as the research object. This study analyzed LER and ESV's spatial and temporal changes over nearly 40 years from 1980 to 2020. LER and LSV were used as ecological elements combined with natural and human-social elements to jointly model the resistance surface of the landscape pattern. Applying the minimum cumulative resistance model (MCR), we identified green ecological corridors, constructed the ESPs of WUA, and proposed optimization measures. Our results show that: (1) The proportion of higher- and high-ecological-risk areas in WUA has decreased from 19.30% to 13.51% over the past 40 years. Over time, a "low-high-low" hierarchical distribution characteristic centered on Wuhan city was gradually formed in the east, south, and north; the total value of ecosystem services increased from CNY1110.998 billion to CNY1160.698 billion. The ESV was higher in the northeastern, southern, and central parts of the area. (2) This study selected 30 ecological source areas with a total area of about 14,374 km2 and constructed and identified 24 ecological corridors and 42 ecological nodes, forming a multi-level ecological network optimization pattern with intertwined points, lines, and surfaces, increasing the connectivity of the ecological network and improving the ecological security level of the study area to a large extent, which is of great significance to promote the ecological priority and green-rise strategy of WUA and the high-quality development path of the green ecological shelter.

Determining the ecological security pattern and important ecological regions based on the supply-demand of ecosystem services: A case study of Xuzhou City, China

The supply-demand for ecosystem services (ESs) is the bridge between ecological security patterns (ESPs) and human wellbeing. This study proposed a research framework of ESP of "supply-demand-corridor-node" and took Xuzhou, China, as a research case, providing a new perspective for the construction of ESPs. The framework was divided into four sections: identifying the ecological source based on the ESs supply; utilizing multi-source economic-social data to characterize the demand of ESs and constructing a resistance surface; defining the ecological corridor in the study area by employing the Linkage Mapper; and identifying crucial ecological protection/restoration areas along the ecological corridor. The results showed that the area of the supply source of ESs in Xuzhou City is 573.89 km², accounting for 5.19% of the city's total area. The spatial distribution of 105 ecological corridors revealed that there were multiple and dense ecological corridors in the middle of the city, but few in the northwest and southeast. A total of 14 ecological protection areas were located primarily in the south of the urban area, and 10 ecological restoration areas were located primarily in the middle and north of the urban area, with a total area of 4.74 km². The findings of this article will be useful in developing ESPs and determining important ecological protection/restoration areas in Xuzhou, China. The research framework could potentially be used in other areas.

Ecosystem Health Evaluation and Ecological Security Patterns Construction Based on VORSD and Circuit Theory: A Case Study in the Three Gorges Reservoir Region in Chongqing, China

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.

Construction of Ecological Security Pattern and Identification of Ecological Restoration Zones in the City of Changchun, China

Identification of crucial regions in need of ecological conservation and restoration based on ecological security patterns is of utmost importance for ecological restoration across national land space with regard to China's promotion of ecological civilization. Using Changchun, the capital of northeast China, as an illustration, the study chooses ecological sources based on the importance of ecosystem services, builds an ecological security pattern using circuit theory, and organizes critical regions for ecological conservation and restoration. The findings reveal that the 20 ecological sources chosen based on ecosystem services are more concentrated on the eastern side of the city, whereas the western side of the city has a smaller overall area; 41 ecological corridors show a network distribution, among which the southeast is relatively densely distributed; 31 ecological pinch points and 15 ecological barrier points are also identified. Prioritized restoration zones, prioritized protection zones, key conservation zones, and general conservation zones were the four different types of ecological restoration regions identified by the study. Each district's prioritized restoration zones in the main metropolitan area are larger than the others; Gongzhuling's priority protection zones are the largest, and Yushu's natural substrate is the best. According to the grading, targeted solutions are suggested, offering helpful advice for the improvement of ecological patterns and ecological restoration of the aforementioned national areas.

Ecological Restoration Strategies for Mountainous Cities Based on Ecological Security Patterns and Circuit Theory: A Case of Central Urban Areas in Chongqing, China

Urban ecosystems are under enormous pressure in the background of rapid urbanization. Mountainous cities are more prone to degradation due to dramatic topography. Ecological security patterns combined with circuit theory can effectively identify ecological barriers and "pinch points" and propose targeted ecological restoration and protection strategies. In order to ensure the ecosystem health and sustainable development of mountainous cities, this paper applies the MSPA model, Invest model, MCR model, and Linkage Mapper Tools to identify the ecological source regions, eco-corridors, and "key points" in the central metropolitan area of Chongqing. The study shows that: (1) There are 43 ecological sources in the central urban area of Chongqing, with a total area of 986.56 km², and it forms a linear distribution with a multi-patch scattering pattern. (2) A series of 86 ecological corridors in the area, totaling 315.14 km, show a pattern of more corridors in the east and fewer in the west. (3) The research found 17 sites totaling 24.20 km of the ecological corridor in the barrier point zone. In addition, up to 22 segments, totaling 19.27 km of the ecological corridor, are located in the "pinch point" zone. (4) The barrier point and "pinch point" on the ecological corridors are identified to obtain their type, scale, and location, thus suggesting conservation-restoration.

Ecological risk changes and their relationship with exposed surface fraction in the karst region of southern China from 1990 to 2020

Due to anthropogenic disturbances, the karst region in southern China is vulnerable to ecological problems such as soil erosion and surface exposure. However, limited studies on variations in large-scale ecological risk (ER) and their influencing factors, particularly the coupling/decoupling relationship with an exposed surface fraction (ESF), make ER regulations and ecological restoration challenging. The present study evaluates the ER of eight typical karst provinces in Southern China from 1990 to 2020 using the technique for order preference by similarity to an ideal solution (TOPSIS) model and ecosystem services (habitat quality, water yield, carbon storage, soil conservation, and food production), and extracts the contemporaneous ESF using Landsat satellite data in Google Earth Engine (GEE). The spatiotemporal change of ER and ESF are analyzed, and their coupling/decoupling relationship and driving mechanism are explored using coupling coordination degree (CCD) and multi-scale geographically weighted regression (MGWR) models. The results show that: (1) Over the past 30 years, the ER has increased until 2010 and subsequently declined, with an increasing mean value (0.463-0.503), except in Chongqing municipality. The ESF decreased significantly (the mean value dropped from 44.7% to 38.7%), except that in Sichuan province. (2) The average CCD between ER and ESF decreased with fluctuation of -0.017, with a decoupling relationship (58.18%). The coupling area is larger than the decoupling area in the Sichuan area, while other provinces are opposite. (3) The coupling/decoupling relationship in the study area is mainly driven by terrain (elevation, slope) and socio-economic (population density, per capita GDP) factors. More attention should be paid to the role of these factors in the continuous reduction and control of ESF and ER. This study can serve as a reference for similar studies in karst regions, such as risk assessment and surface monitoring, rocky desertification control, ecological engineering layout, and territorial planning.

Review on Eco-Environment Research in the Yellow River Basin: A Bibliometric Perspective

The Yellow River Basin (YRB) is an important economic zone and ecological barrier in China. The analysis of its research characteristics and hotspots has been helpful to grasping the future research direction. This work carried out text mining and analysis on scientific papers related to eco-environment research in the YRB from English and Chinese publications. It showed that: there was a fluctuating upward trend over the past 30 years, which was closely related to major events in the YRB during the same period. Chinese research institutions have a closer cooperation with the USA, Australia and other developed countries. More articles were from high-quality journals in ecology, the environment, and others. Interestingly, research institutions with more Chinese articles were mainly located around Beijing or the YRB. Additionally, from a research object perspective, both the English and Chinese articles have mainly focused on large areas such as the lower Yellow River, the middle reaches of the Yellow River, and the upper reaches of the Yellow River, then turning to small areas such as the Yellow River estuary and the source area of the Yellow River. Eco-environment research in the YRB has involved multiple disciplines, and "water-soil-vegetation-ecological protection" has been widely concerned. From the evolution law of hot topics, it has shown a transformation from quantity to quality, from utilization to management, from macro to micro, from construction to high-quality development. It suggests that future research should focus on water, soil, the ecological environment and local high-quality development in small regions and small watersheds.