Ecological network analysis for virtual water trade system: A case study for the Baiyangdian Basin in Northern China

Multiplex dependence analysis of China's interprovincial virtual water based on an ecological network

The interprovincial circulation of goods and services has formed virtual water flows between regions, which can redistribute water resources. Based on previous virtual water trade research, this study further explored the multiple dependencies of virtual water, i.e., direct, indirect, and complete dependence. This study examined the direct, indirect, and complete dependence of virtual water between provinces in China by constructing multilayer dependence networks and identified the key regions and paths of virtual water trade network. The results showed direct dependence was the densest and had the largest overall dependence degree, but indirect dependence was the most stable and orderly. Second, the dominant provinces were Guangxi, Hunan, Sichuan, Xinjiang, and Anhui, referred to as "core‒five‒region," and the flow relevant to them accounted for approximately 30% of the virtual water. The seven provinces of Shanxi, Zhejiang, Shandong, Hubei, Guangdong, Shaanxi, and Gansu depend both directly and indirectly on the "core‒five‒region." Shanxi and Zhejiang have close direct and indirect dependence, with more than one of the "core‒five‒region." Guangdong was the province with the most direct and indirect input of virtual water from the "core‒five‒region." The study provides a scientific basis for multiregional identification for the collaborative management of water resources in China from the perspective of dependence.

Ecological network analysis of industrial wastes metabolism based on input-output model for Jiangsu, China

The enormous discharge of industrial waste seriously hinders the sustainable development of cities. However, most studies only involve a single or limited category of industrial pollutants, ignoring the environmental pressure caused by multiple resources and environmental factors. This paper combines input-output analysis and ecological network analysis to construct an industrial waste metabolic input-output (IWMIO) model, which explores the industrial waste discharge and discharge relationships among different sectors in Jiangsu Province from the three aspects of industrial wastewater, industrial waste gas, and industrial solid waste. The results show that the indirect discharge of industrial waste is greater than the direct discharge in the industrial waste metabolism system. TI (Tertiary industry), CI (Chemical industry), SPM (Smelting and pressing of metals), and PSEH (Production and supply of electricity and heat) dominate the industrial waste metabolism system. In addition, MWC (Mining and washing of coal), MNMP (Manufacture of non-metallic mineral products), SPM (Smelting and pressing of metals) have more mutualism and competition relationships with other sectors, so the control of industrial waste discharge in these sectors contributes to achieving emission reduction targets. Based on the research results, this paper proposes corresponding policy recommendations such as considering both direct and indirect emissions of sectors when formulating waste reduction policies and developing pertinent industrial waste reduction programs based on the characteristics of the identified sectors. The results of this paper are helpful to identify the dependence and influence relationships of various sectors in the industrial waste metabolism system, promote industrial waste discharge control, and provide theoretical support for the adjustment of industrial structure and the formulation of related policies in Jiangsu Province.

Development of Method for Assessing Water Footprint Sustainability

Large scale production of water-intensive industrial products can intensify water scarcity, resulting in potential unsustainable water use at local and regional scales. This study proposes a methodological framework for assessing the WF sustainability of multiple interdependent products in a system, and one of China’s four major large modern coal chemical industry bases is used as a case study. A Mixed-Unit Input-Output (MUIO) model was applied to calculate the blue water footprint (WF) for 19 major coal-based energy and chemicals in the study area, based on which the WF sustainability of production of the products were assessed using different indicators. Technical coefficient matrix and direct water consumption vector of the products were constructed based a database that were built by field research in the study area. Accounting result indicates that the blue WF of the coal-based products range from 2.5 × 10−4 m3/kWh for coal-fired power to 55.25 m3/t for Polytetrahydrofuran. The sustainability assessment reveals that the blue WF of all products produced in the study area are sustainable at both product and regional levels, while over half of them have reached the advanced level. However, the blue WF of a few products with large production capacities has just crossed the sustainable thresholds, posing potential threat to the local environment. This paper concludes with a discussion on the choice of blue WF accounting approach, methods to promote WF sustainability of coal-based products, and suggestions for the WF management in general.

Identifying optimal virtual water management strategy for Kazakhstan: A factorial ecologically-extended input-output model

Virtual water is an important indicator measuring the amount of water needed from the perspective of consumption, which can help decision makers to identify desired system design and optimal management strategy against water resources shortage. In this study, a novel model named as factorial ecologically-extended input-output model (abbreviated as FEIOM) is developed for virtual water management. FEIOM integrates techniques of input-output model (IOM), ecological network analysis (ENA) and factorial analysis (FA) into a general framework. It is effective to evaluate the virtual water flows, reveal ecological inter-connections in virtual water system (VWS), and identify key water consumption sectors that have significant individual and interactive effects on VWS's performance. FEIOM is then applied to identifying optimal virtual water management strategies for Kazakhstan in Central Asia. The main findings are: (i) Kazakhstan is a net importer of virtual water (reaching up to 46.0 × 10⁹ m³), demonstrating that the national economic structure is reasonable, which can abate the national water scarcity and improve its eco-environmental protection; (ii) the virtual water of agricultural sector is net exporter, where vegetables, fruits and nuts occupy 86% of the total agricultural exports; the massive export of water-intensive products further squeezes the water for other users; (iii) the key factors affecting the national VWS are agriculture > primary manufacturing > advanced manufacturing > services. Therefore, from solving water resources shortage and facilitating sustainable development perspectives, Kazakhstan should stimulate the domestic primary manufacturing productions and improve agriculture and advanced manufacturing water-use efficiencies.

Ecological network analysis of an urban water metabolic system: Integrated metabolic processes of physical and virtual water

The contradiction between social economy and water environment has become increasingly prominent, and the analysis of urban water metabolism system (UWMS) represents a problem-solving approach from the perspective of the entire flow process. However, a comprehensive UWMS model that considers both physical and virtual water flows is currently lacking. This paper presents an innovative application of an ecological network model of the UWMS-integrated metabolic process of physical and virtual water in Xining during the 2002-2018 period. By analysing and screening the metabolic characteristics, metabolic structure and metabolic relationships, the sustainability of the UWMS is evaluated in depth, and the main causes and critical compartments of the unhealthy metabolic process are identified. The findings show that the UWMS in Xining maintains a moderate level of robustness (the average R = 0.48) with limited metabolic efficiency. Since 2012, the water management policies in Xining have been significantly strengthened, contributing to a slight increase in robustness by improving the water use efficiency and metabolic structure. The integrated metabolic process is unhealthy because the metabolic structure is not reasonable, and the systematic metabolic relationship tends to be antagonistic due to the network mutualism index dropping to 1.0 during 2016-2018. We conclude that efficient irrigation management, more infrastructure projects for the sewer network, wastewater treatment and recycling could provide effective support to enhance the coordinate development of the social economy and water environment in Xining.

Competition and Exploitation for Ecological Capital Embodied in International Trade: Evidence from China and Its Trade Partners

In order to identify ecological relationships of participating countries in the transfer system of ecological capital embodied in global trade, this paper takes the international trade of China and its partners from 2002 to 2017 as a case, and uses the ecological footprint (EF) measured by the optimized product land-use matrix (PLUM) method to quantify ecological capital for the value of macro-ecological resources, then uses the ecological network analysis (ENA) method to construct a complete transfer network of trade-embodied ecological capital and uses a utility analysis to identify ecological relationships between trading countries. Our results show that: (1) Throughout the study period, competition relationships with 61% dominated in the network, and the countries that have a pair-wise competition relationship with China are mainly located in central and western Europe, northeastern Europe, North America, southern Asia and eastern Asia. (2) Indirect utility determines the dominant ecological relationship in system, and it mainly converts dominant ecological relationships from control to competition by transforming exploit into competition. (3) China is looking to creating a more mutually beneficial trading environment at the expense of its own interests. (4) A global crisis event is likely to result in the control of ecological capital in more countries, and in its aftermath, the world is likely to be in a highly competitive environment. Reducing ecological capital consumption by improving energy efficiency and optimizing the global trading environment into a trading system dominated by mutualism relationships can be effective ways for countries around the world to achieve sustainable development post-COVID-19 crisis.

Economic sensitivity analysis of dual perspectives induced by energy scarcity for energy-dependent region

Rapid industrialization leads to potential energy scarcity. The formulation of energy intervention can alleviate the economic losses caused by insufficient energy inputs in advance. In this study, the energy dependency and sensitivity quantification model (EDSQ) is firstly developed to evaluate the impacts of insufficient energy support on economic development under network-based perspective and sector-based perspective. A special case study for the Province of Shanxi, China, is conducted to illustrate the potential benefits of its use in the formulation of energy intervention for energy-dependent regions. Seven energy groups are explored to gain more insights into the impacts of specific energy groups on energy metabolism and the complicated interactions among sectors. It is found that the energy metabolism of Shanxi is under an unhealthy state. The internal flows are dominated by exploitation and competitive relationships, which is not conducive to effective energy metabolism. The hierarchy analysis indicates that the pulling force is hardly affected by the classified energy groups but the driving force is sensitive, which further reveals that the producers can choose different energy sources according to their production structure. Faced with potential energy scarcity, the shortage of coal may bring considerable economic losses. The energy intervention should be formulated for the sectors that are less dependent on energy. However, it is not recommended to curb energy use in the petroleum, coking, nuclear fuel processing and coal mining sectors, because their sectoral losses can impose significant losses to the entire network. Thus, the scientific results of this study can provide academic support for quantifying the impact of potential energy scarcity, and guide the formulation of energy intervention to achieve sustainable development for energy-dependent regions.

The Impact of Virtual Water on Sustainable Development in Gansu Province

The concept of virtual water, as a new approach for addressing water shortage and safety issues, can be applied to support sustainable development in water-scarce regions. Using the input-output method, the direct and the complete water use coefficients of industries categorized as primary, secondary, or tertiary, and the spatial flow patterns of the inter-provincial trade in the Gansu province region of China, were explored. The results show that in 2007, 2010, and 2012 the direct and complete water use coefficients of the primary industries were the greatest among the three industry categories, with direct water use coefficients of 1545.58, 882.28, and 762.16, respectively, and complete water use coefficients of 1692.22, 1005.38, and 873.44, respectively; whereas, the direct and complete water use coefficient values of the tertiary industry category were the lowest, with direct water use coefficients of 16.65, 7.74, and 66.89 for 2007, 2010, and 2012, respectively, and complete water use coefficients of 65.46, 66.89, and 72.81 for 2007, 2010, and 2012, respectively. In addition, study results suggest that the volume of virtual water supplied to Gasnu province’s local industries has decreased annually, while virtual water exports from the province have increased annually, with the primary industry accounting for 95% of virtual water output. Overall, the virtual water of Gansu province in 2010 showed a net output trend, with a total output of 0.506 billion m3, while in 2007 and 2012 it showed a net input trend with a total input of 0.104 and 1.235 billion m3, respectively. Beijing, Shanghai, Guangdong, Ningxia and other water-scarce areas were the main input, or import source for Gansu’s virtual water; during the years studied, these provinces imported more than 50 million m3 individually. Based on these results, it is clear that under the current structure, virtual water is mainly exported to the well-developed coastal areas and their adjacent provinces or other water-abundant regions. Therefore, Gansu province should (1) adjust the industrial structure and develop water-saving and high-tech industries; (2) adjust the current trade pattern to reduce virtual water output while increasing its input to achieve balanced economic development and water resource security.

Unfolding interregional energy flow structure of China's construction sector based on province-level data

The construction sector is a critical part in achieving energy conservation targets in China, as it accounts for approximately 30% of the annual national energy supply for building construction. Therefore, this study integrates multi-regional input-output analysis and ecological network analysis to track energy fluxes and pathways from the construction sector, aiming to facilitate the configuration of the energy-flow structure and improve understanding of the region's responsibilities. Results of a spatial distribution analysis show that the eastern area of China leads in fossil energy consumption (e.g., coal and crude oil), whereas western China is the largest consumer of natural gas. Spatial relationship analyss indicate that eastern areas are located at the top of the trophic structure, implying that these regions are prioritized in energy consumption over the surrounding regions. By contrast, most regions located in the northern parts of China are characterized by resource-abundant areas and are at the bottom of the trophic structure, thereby indicating their comparatively weak role in an exploitation relationship. An investigation of major metropolitan areas demonstrates that mandatory targets set by national instruments are stratified in accordance with their diverse role and status in energy consumption at the beginning of the 12th Five-Year Plan period. However, these targets remain insignificant in the context of the inner area.

Simulation of coupled impact-management response scenarios for distributed wastewater environmental discharges at basin scale through urban environmental risk network transmission mechanism

A multi-agent modeling method is applied here to model the coupled environmental impact and management response scenarios in relation to the impact of multiple wastewater discharges at river basin scale. Based on the Netlogo modeling platform, the cumulative impact of water pollution, which was represented here by COD values, is esteemed using Huaihe River Basin (China) as a case study. As a novel factor, different management responses to the adverse effects of cumulative pollution level increases along the river are also considered in the simulation processes. Based on 45 alternative scenarios, the model displayed its ability to represent the coupled dynamics along time between pollution propagation and management actions (described according to their occurrence, responsiveness and characteristics). Besides the most trivial results, which demonstrate the efficacy of the model in representing the simulated reality, an interesting result is that, the management responses to pollution propagation are more effective when the river basin authorities do not take any coercive policies. This might depend on the fact that excessive restraints have a dependence on their underlying mechanism, thus limiting a spontaneous reaction to pollution episodes. It is important, however, to stress the role of ecological education, in parallel to management, to limit the necessity of top-down approaches in the river system management measures.

Ecological network analysis of growing tomatoes in an urban rooftop greenhouse

Urban agriculture has emerged as an alternative to conventional rural agriculture seeking to foster a sustainable circular economy in cities. When considering the feasibility of urban agriculture and planning for the future of food production and energy, it is important to understand the relationships between energy flows throughout the system, identify their strengths and weaknesses, and make suggestions to optimize the system. To address this need, we analyzed the energy flows for growing tomatoes at a rooftop greenhouse (RTG). We used life cycle assessment (LCA) to identify the flows within the supply chain. We further analyzed these flows using ecological network analysis (ENA), which allowed a comparison of the industrial system to natural systems. Going beyond LCA, ENA also allowed us to focus more on the relationships between components. Similar to existing ENA studies on urban metabolism, our results showed that the RTG does not mimic the perfect pyramidal structure found in natural ecosystems due to the system's dependency on fossil fuels throughout the supply chain and each industry's significant impact on wasted energy. However, it was discovered that the RTG has strong foundational relationships in its industries, demonstrating overall positive utility; this foundation can be improved by using more renewable energy and increasing the recycling rates throughout the supply chain, which will in turn improve the hierarchy of energy flows and overall energy consumption performance of the system.

The spatiotemporal variation analysis of virtual water for agriculture and livestock husbandry: A study for Jilin Province in China

With the rapid development of economic, water crisis is becoming more and more serious and would be an important obstacle to the sustainable development of society. Virtual water theory and its applications in agriculture can provide important strategies for realizing the reasonable utilization and sustainable development of water resources. Using the Penman-Monteith model and Theil index combining the CROPWAT software, this work takes Jilin Province as study area quantifying the virtual water content of agriculture and livestock husbandry and giving a comprehensive evaluation of their spatiotemporal structure evolution. This study aims to help make clear the water consumption of agriculture and livestock husbandry, and offer advice on rational water utilization and agricultural structure adjustment. The results show that the total virtual water (TVW) proportion of agriculture presents a gradual growth trend while that of livestock husbandry reduces during the study period. In space, central Jilin shows the highest virtual water content of agriculture as well as livestock husbandry, the TVW in central Jilin is about 35.8billionm³. The TVW of maize is highest among six studied crops, and the cattle shows the highest TVW in the four kinds of animals. The distribution of TVW calculated by us and the distribution of actual water resources have remarkable difference, which leads to the increase of water consumption and cost of agricultural production. Finally, we discuss the driving force of the spatiotemporal variation of the TVW for agriculture and livestock husbandry, and also give some advises for the planting structural adjustment. This work is helpful for the sustainable development of agricultural and livestock husbandry and realizing efficient utilization of water resources.

Virtual water and water self-sufficiency in agricultural and livestock products in Brazil

Virtual water trade is often considered a solution for restricted water availability in many regions of the world. Brazil is the world leader in the production and export of various agricultural and livestock products. The country is either a strong net importer or a strong net exporter of these products. The objective of this study is to determine the volume of virtual water contained in agricultural and livestock products imported/exported by Brazil from 1997 to 2012, and to define the water self-sufficiency index of agricultural and livestock products in Brazil. The indexes of water scarcity (WSI), water dependency (WDI) and water self-sufficiency (WSSI) were calculated for each Brazilian state. These indexes and the virtual water balance were calculated following the methodology developed by Chapagain and Hoekstra (2008) and Hoekstra and Hung (2005). The total water exports and imports embedded in agricultural and livestock products were 5.28 × 10¹⁰ and 1.22 × 10¹⁰ Gm³ yr^-1, respectively, which results in positive virtual water balance of 4.05 × 10¹⁰ Gm³ yr^-1. Brazil is either a strong net importer or a strong net exporter of agricultural and livestock products among the Mercosur countries. Brazil has a positive virtual water balance of 1.85 × 10¹⁰ Gm³ yr^-1. The indexes used in this study reveal that Brazil is self-sufficient in food production, except for a few products such as wheat and rice. Horticultural products (tomato, onion, potato, cassava and garlic) make up a unique product group with negative virtual water balance in Brazil.

Ecological network analysis for a virtual water network

The notions of virtual water flows provide important indicators to manifest the water consumption and allocation between different sectors via product transactions. However, the configuration of virtual water network (VWN) still needs further investigation to identify the water interdependency among different sectors as well as the network efficiency and stability in a socio-economic system. Ecological network analysis is chosen as a useful tool to examine the structure and function of VWN and the interactions among its sectors. A balance analysis of efficiency and redundancy is also conducted to describe the robustness (RVWN) of VWN. Then, network control analysis and network utility analysis are performed to investigate the dominant sectors and pathways for virtual water circulation and the mutual relationships between pairwise sectors. A case study of the Heihe River Basin in China shows that the balance between efficiency and redundancy is situated on the left side of the robustness curve with less efficiency and higher redundancy. The forestation, herding and fishing sectors and industrial sectors are found to be the main controllers. The network tends to be more mutualistic and synergic, though some competitive relationships that weaken the virtual water circulation still exist.

Ecological network analysis for economic systems: growth and development and implications for sustainable development

The quantification of growth and development is an important issue in economics, because these phenomena are closely related to sustainability. We address growth and development from a network perspective in which economic systems are represented as flow networks and analyzed using ecological network analysis (ENA). The Beijing economic system is used as a case study and 11 input-output (I-O) tables for 1985-2010 are converted into currency networks. ENA is used to calculate system-level indices to quantify the growth and development of Beijing. The contributions of each direct flow toward growth and development in 2010 are calculated and their implications for sustainable development are discussed. The results show that during 1985-2010, growth was the main attribute of the Beijing economic system. Although the system grew exponentially, its development fluctuated within only a small range. The results suggest that system ascendency should be increased in order to favor more sustainable development. Ascendency can be augmented in two ways: (1) strengthen those pathways with positive contributions to increasing ascendency and (2) weaken those with negative effects.