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Abstract A stable and reliable urban energy supply is essential for supporting sustainable regional and even national development. Further, a general definition and method is necessary to comprehensively evaluate urban energy supply security for different energy resources, identify key problems, and conduct regulations. Therefore, ecological network analysis (ENA) is introduced as a general systematic analysis tool to simulate and assess urban energy supply security, based on the idea that various components related to energy supply exist and interact in a common network. The proposed ENA model was used to evaluate and compare the security of coal, crude oil, and natural gas supplies for Beijing during 1997–2012. The evaluation included overall sustainability assessment, system property analysis, and structure analysis of energy supply systems. The results showed that the coal supply had the highest level of supply security, followed by the crude oil supply and then the natural gas supply. In addition, the crude oil supply system showed the most competitiveness in terms of the energy supply systems' properties. Scenario analysis yielded suggestions for improving urban energy supply security by maintaining energy production, increasing energy consumption within a certain range, strengthening and diversifying supply sources, and increasing strategic energy reserves. The ENA-based general model provides a useful tool for systematic evaluation of urban energy security from the supply perspective to quantitatively support urban energy management. Highlights • Ecological network analysis is applied to evaluate urban energy supply security. • A general network model of urban energy supply systems is established. • The supply security of coal, crude oil, and natural gas in Beijing are evaluated. • Different energy supply systems are compared via structure and property analysis. • Suggestions based on scenario analysis are given to improve energy supply security. [ABSTRACT FROM AUTHOR]

A stable energy supply is essential to support urban socioeconomic activities and to ensure urban sustainable development. A quantitative systematic method is necessary to evaluate and improve the security level or urban energy supply. Ecological network analysis (ENA) is thus applied as a useful general analysis tool to systematically simulate, evaluate, and compare energy supply security in different cities. Based on the established ENA model, we evaluated and compared the crude oil supply security for Beijing, Shanghai, and Tianjin from 1997 to 2012, via sustainability, stability, and structure analyses. The results indicate that the overall levels of crude oil supply security for the three cities showed similar features and increase trends during the study period, whereas the key influencing compartments were different. Correspondingly, related suggestions were proposed to improve urban crude oil supply security based on further scenario analysis, including diversifying supply sources, maintaining domestic supply, improving internal crude oil production, increasing consumption within a certain range, and strengthening strategic reserves, with different emphases for different cities. The ENA-based general method provides a new perspective on the systematic evaluation and regulation of urban energy supply security, which can support urban energy policymaking. [ABSTRACT FROM AUTHOR]

Energy has become a scarce global strategic resource, and energy supply security is receiving increasing attention. A common evaluation platform is necessary to systematically understand the supply security levels of different energy sources and help make the national energy strategy. Ecological network analysis (ENA) is thus regarded as a useful common tool to systematically simulate, evaluate, and compare the supply security for different energy sources, when considering the fact that modern energy systems have formed a complex global energy network through extensive energy trading. Based on the established ENA platform, we evaluated and compared China's crude oil and natural gas supply security from 2000 to 2012. To this end, we assessed the overall security level, investigated the relationship among different compartments within the network system, determined the system's structure, and analyzed the system's properties. It was found that the Chinese crude oil supply security level was higher than that of the natural gas supply and that the crude oil supply system was more mature in terms of multiple properties. Suggestions are proposed to improve the Chinese energy supply security based on further scenario analysis, including increasing domestic energy production, controlling energy consumption, diversifying foreign supply sources, and strengthening the strategic reserve. The ENA-based common platform can be used for the systematic evaluation and improvement of energy supply security and further support national energy policymaking for both developed and developing countries, both energy importers and exporters. [ABSTRACT FROM AUTHOR]

As a relatively clean energy, natural gas will be increasingly in demand to meet short-term low-carbon targets. The gap between the demand and supply of natural gas will be increasingly scrutinized, which highlights the significance of natural gas supply security. Considering the extensive connections among various aspects related to natural gas supply and the complex interactions behind these connections, ecological network analysis was applied to simulate the natural gas supply system in China and systematically measure its overall security level. Network Information Analysis, Structural Analysis, and Utility Analysis were conducted. It is found that the Chinese natural gas supply security increased during 2000–2011. In terms of the influence of different compartments on the whole natural gas supply system, in order from the largest to smallest influence they are: supply sources, consumption sector, refining, and reserve sectors. And the relationships among compartments became stronger in the later stage than that in the earlier stage of the study period. Suggestions on improving China’s natural gas supply security were proposed based on the results and further scenario analysis. The network model developed herein is a new perspective for natural gas supply security assessment, which can be used as guidance for policy making. [ABSTRACT FROM AUTHOR]

Highlights: [•] We developed an ecological network model for an urban system. [•] We studied Beijing's ecological hierarchy using ecological network analysis. [•] The hierarchy's layout was determined by means of utility analysis. [•] The top (consumer) level of the hierarchy exerts too much pressure on lower levels. [•] The recycling sector must improve its capacity to better support the system. [Copyright &y& Elsevier]

Abstract: The importance of addressing cumulative environmental impact of large development projects on rivers has been increasingly highlighted. Consideration to potential impact pathways may be difficult, however, without appropriate analytical methods. By introducing ecological network model, this paper focuses on the quantification of the cause-effect relationships inherent the cumulative effects of dam construction from a holistic perspective. With Lancang river of Longitudinal Range-Gorge Region (LRGR) as an example, the risk-based interaction instead of the conventional energy or material flow of ecological network model has been created to conceptualize the cumulative effects network model. Based on this model, the network structural and functional analysis were adjusted for the assessment of potential eco-environmental impact within the ecosystem, thus demonstrating how the risk-based ecological network analysis can be used to characterize the holistic cumulative effects of dams on the temporal and spatial scale. [Copyright &y& Elsevier]

Abstract: Dam construction results in variations of hydrology, river morphology and habitat and the biota associated with the reservoir change significantly compared to the assemblage before dam construction in order to match these changed environmental conditions. Some attempts so far have been made to ascertain the changed properties of aquatilia due to dam construction. Most of them, however, were focused on perturbances to single factors, such as rearing habitats, reproduction and migration routes, etc. Few have been done on the performance of aquatilia from the whole-ecosystem perspective. Herein, we evaluate the structural properties of aquatic animals and their complex ecological relationships within the ecosystem before and after dam construction based on ecological network analysis. This study provides a feasible way for integral ecosystem evaluation with the application of ecological network analysis to river ecosystem subjected to human disturbance. [Copyright &y& Elsevier]

To identify the key contributors of urban carbon emissions as well as the acting paths, it is necessary to analyze the carbon flows from a systematic perspective. Thus, the concept of urban carbon metabolism was introduced in this paper and correspondingly input-output analysis (IOA) and ecological network analysis (ENA) were combined to conduct the carbon metabolism analysis. Concretely speaking, the urban IO table was compiled based on the provincial one and then the direct and embodied urban carbon flows were accounted. Subsequently, the carbon metabolic network model was established, through which the characteristics of the metabolic network were further analyzed to better reveal the contributors and influencing factors of carbon emissions. Dongguan, a city famous as the "factory of the world", was chosen as the case. The results indicate that the total direct and embodied carbon flows were mainly concentrated in manufacture. Manufacture was found to be major factors affecting other compartments through indirect interplay. A trophic hierarchical structure was found, where compartments can be classified into primary producers, secondary producers, primary consumers and secondary consumers according to their metabolic characteristics in use of energy. Electricity, gas & water were defined as secondary producer, and its self-induced carbon flows accounted for more than 95% of the carbon flow conversion within this compartment. By further comparing the metabolic characteristics in Dongguan with that of Guangdong Province and other cities, measures were suggested to heighten energy utilization efficiency and promote positive interactions among compartments to promote the carbon emission reduction in Dongguan. • A new method to compile the input-output table of urban carbon flows is proposed. • The direct and embodied carbon flows are accounted via input-output analysis (IOA). • The interactions among sectors is checked using ecological network analysis (ENA). • The carbon metabolism of Dongguan is analyzed by combining IOA and ENA. [ABSTRACT FROM AUTHOR]

With the accelerating pace of globalization, uncertainty and unknown risks within open and complex urban systems increase with the occurrence of problems such as the conflict between humans and natural land use, water scarcity, and the continuing loss of biodiversity. Thus, the improvement of urban resilience has emerged as an important issue in the context of global urbanization. However, a knowledge gap remains in its evaluation from the perspective of systematic resource/element metabolic processes. To understand the urban resilience response mechanism better and depict metabolic processes systematically, an urban resilience assessment framework of "robustness-adaptability-restorability-coordination" based on the cross-media carbon metabolism network model was established. Principles of material flow analysis and ecological network analysis were applied to examine the urban resilience of Guangzhou, China, from 2010 to 2020. Results showed the urban resilience level decreased from a carbon metabolism perspective during the study period. This was reflected in an overall decline in system robustness and restorability, relatively unchanged adaptability, and a non-beneficial coordination relationship. Recommendations such as regulating key sectors (e.g., agriculture and construction) were proposed to improve urban resilience. This research will bring a new insight into future urban resilience assessment and contribute the urban sustainable development. [ABSTRACT FROM AUTHOR]

• Investigate the urban cross-media carbon metabolism network structure systematically. • Identify the key nodes and paths of the urban cross-media carbon metabolism network. • MFA and ENA were employed to establish the network and evaluate its structure. • The construction and transportation sectors were identified as key nodes. • Collaborative regulation of key nodes/paths benefits the system improvement better. Optimizing the structure of the carbon metabolic network is essential for enhancing network performance. However, a knowledge gap remains in systematically evaluating the network structure and comprehensively identifying the key nodes and paths, particularly in a carbon metabolism system that involves the frequent transition of carbon element across the air, water, and soil mediums. Hence, taking Guangzhou, China, as a case study, we constructed a cross-media metabolism network model based on material flow analysis. Subsequently, the general structural characteristics and key nodes/paths of the network were investigated through the integration of trophic structure analysis, contribution analysis, and stability analysis in ecological network analysis. The results primarily suggest that the connections among nodes in the carbon metabolism network have become looser, and the metabolic system structure was in a medium state with some defects from 2010 to 2020. Sectors of construction and transportation, as well as carbon flows from the agriculture sector to the construction sector and the energy conversion sector to the transportation sector, were identified as the key nodes and paths influencing the structural characteristics. Subsequently, twenty-one optimization scenarios were developed, with the results suggesting the advantage of collaborative regulation of key nodes/paths (e.g., increasing the carbon flows both from the agriculture sector to the construction sector and from the energy conversion sector to the transportation sector by 50%). This work may provide useful guidance for the structure optimization of the carbon metabolism system. [ABSTRACT FROM AUTHOR]

In this paper, we develop a spatially explicit model of carbon transfers between regions of an urban area. The carbon transfers represent the metabolic processes due to regional land use changes. We used the model to identify spatial heterogeneity in the carbon metabolic structure, functions, and relationships within the network. Data for Beijing from 1990, 1995, 2000, 2005, and 2010, were combined with empirical coefficients, to construct the network. We used ecological network analysis to analyze the structure and function of the network, and to determine the ecological relationships between the components of the system, their distribution, and their changes over time. The analysis revealed that carbon throughflow of the network decreased and positive relations mostly outweighed negative relations. Exploitation relationships were the dominant type in Beijing during most of the study period, particularly in the northwest before 2000, but moved towards the southeast over time, leaving competition relationships with losses of benefits dominant in the northwest. Mutualism relationships with mainly beneficial carbon flows were dominant in the southeast, increasing in frequency in this region throughout the study period. The results provide a theoretical basis for planning adjustments to the city's structure to achieve low-carbon goals. [ABSTRACT FROM AUTHOR]

To alter the sharply decreasing trend of biodiversity due to human disturbances, much emphasis has been placed on the ecological networks comprised of core areas with high ecological significance and corridors connecting them. The purpose of this paper is to introduce a novel viewpoint and method to identify, analyze and optimize the ecological network of Wuyishan City. The bidirectional least-cost distance model is applied to identify the landscape network in Wuyishan City for the year 1995 and 2005, which can incorportate digraph in ecological network modeling, overcome the limitation of failing to reflect the orientation of the species' dispersal process, and make the process of modeling more convincing by distinguishing flux orientation of “go” and “return” of two random patches. Three new metrics, i.e., network cyclicity, degree of cyclicity, and degree of connectedness, which can quantify the integrity and continuity of network and the relation between network organization and ecological process, are introduced to measure the presence and strength of cyclic pathways in a network and reflect the network's ability to transfer bio-flux. The results show that the ecological network of Wuyishan City in the year 1995 and 2005 have respectively a network size of 18 and 17, degree of connectedness of 1 and 0.7647, network cyclicity of 7.1378 and 8.2570, and degree of cyclicity of 0.3965 and 0.4857, which indicate that the network in Wuyishan City for the year 2005 has strong ability to transfer bio-flux, a high level of eco-process diversity, and a low level of integrity and continuity. It can be concluded that during the past 10 years, different areas of Wuyishan City have gone through landscape degradation and restoration. In the northeast, network components degraded severely and made several patches “isolated islands”, while in the southwest, the network has been developed because of landscape restoration. In particular, the linkages among the patches of natural reserve and its neighborhood increased remarkably, which directly increased the interaction strength and the whole network cyclicity. Then, via scenario analysis, we also identify the patches and linkages that make great contributions to the entire cyclicity and connectedness, such as patches [1,2,3,4,5,6] (Nature reserve and its neighborhood), [12] (bridging the north and west part) and [19] (bridging the south and west part), and linkages among the central patches. [ABSTRACT FROM AUTHOR]