Food Subsystems Research Articles

The Coupling Coordination Degree and Its Driving Factors for Water–Energy–Food Resources in the Yellow River Irrigation Area of Shandong Province

Water resources, energy, and food are essential for the development of society, and they are strongly interdependent. The coupling and coordination relationships of the water–energy–food (WEF) system are important for regional resource security and high-quality development. The Yellow River Irrigation Area in Shandong Province, China, is a grain production base and has a substantial impact on national food security. To examine the water, energy, and food subsystem dynamics in this area, an evaluation system for the WEF system was established. A comprehensive weighting method based on game theory was employed to determine index weights. TOPSIS was used to assess the development level of the WEF system. A coupling coordination degree model was used to analyze the evolution of the coupling coordination degree of the WEF system from 2000 to 2020, and a GWR model was constructed to explore the spatial heterogeneity of its driving factors. The findings indicated that the development level of the WEF system in the study area was moderate, with a gradual upward trend. The coupling coordination degree fluctuated between 0.62 and 0.739. The GWR model revealed that temperature had an overall negative effect on the coupling coordination degree, with the greatest impact on the central irrigation area; the slope and NDVI had a negative effect, with increasing intensity from the southwest to the northeast; and rainfall had an overall positive effect, with the greatest impact on the irrigation area near the estuary in the northeast. Overall, the building area ratio had a negative effect on the coupling coordination degree, with exceptions in some areas. These research outcomes provide theoretical support for sustainable agricultural development in the Yellow River irrigation areas of Shandong Province and methodological reference data for studying collaborative resource utilization in irrigation regions.

Coupling Coordination Degree of Land, Ecology, and Food and Its Influencing Factors in Henan Province

Studying the spatiotemporal evolution characteristics of the coupling coordination of the land–ecology–food system (LEF) aids in promoting green agricultural development and regional resource management. This study enriches food indicators under the dietary structure and uses the coupling coordination degree model to analyze the coupling coordination relationship among the LEF of 18 cities in Henan Province from 2011 to 2020. The gray relational degree model is used to investigate the main influencing factors determining the synergistic development of the system. The results show that the comprehensive development index of the LEF in Henan Province ranges between 0.4 and 0.6. The overall comprehensive evaluation index of various cities is ranked as Southern Henan > Eastern Henan > Central Henan > Northern Henan > Western Henan, with the greatest fluctuation observed in the food subsystem. During the study period, the coupling degree of Henan’s LEF ranged from 0.277 to 0.996, indicating stages from low- to high-level coupling. The coupling coordination degree ranged from 0.338 to 0.775, generally bordering on imbalance and barely coordinated. The impact of each subsystem evaluation index on the system’s coupling coordination degree can be ranked as food subsystem > ecology subsystem > land subsystem, with the correlation degree of internal indicators of the food and ecology subsystems with the system’s coupling coordination degree being over 85%, emphasizing the importance of strict management. In summary, the coupling coordination of the LEF system in Henan Province urgently needs to be improved; especially, the coordination of the agricultural system is particularly important. Clarifying the spatiotemporal pattern of the LEF coupling and its coordination can provide a scientific basis for the coordinated development of land use, agricultural ecology, and grain production in Henan Province.

Research on the synergy of the water–energy–food composite system in the Beijing–Tianjin–Hebei region

ABSTRACT Water, energy, and food are interdependent and mutually restrictive, and changes in any one resource may have an impact on the others. In order to promote the sustainable utilization of resources, it is important to study the synergy of the water–energy–food composite system (WEFCS). Taking the Beijing–Tianjin–Hebei region as an example, this study adopts the composite system synergy degree model to quantitatively measure the synergy degree of WEFCS from 2011 to 2021, then constructs an evolutionary model to identify the interactions between the subsystems, and finally analyzes the interactions dynamically by using the panel vector autoregression model. The results show that the WEFCS synergy level in the Beijing–Tianjin–Hebei region is generally basic and shows low stability during the study period. Regional subsystems are more dependent than collaborative or competitive. Moreover, the regional water subsystem has a short-term positive impact on the energy subsystem, the energy subsystem has a short-term negative impact on the food subsystem, and the food subsystem has a delayed and complex influence on the water and energy subsystems, with the water subsystem being particularly affected. This study provides a decision-making basis for policymakers to optimize resource allocation.

Can Green Finance Be a Regulator of “Water–Energy–Food” Synergy? Evidence from the Yangtze River Delta

The synergistic relationship between water, energy, and food faces increasing challenges. Green finance as a policy tool promotes high-quality and efficient development of water, energy, and food subsystems. However, whether it can improve the synergistic relationship of “water–energy–food” (WEF) still needs to be studied. Using the panel data of 38 prefecture-level cities in the Yangtze River Delta (YRD) from 2013 to 2021, and network DEA and panel regression models, we study the impact of green finance on the level of synergy of “water–energy–food”. The results of the study show that green finance can promote the synergy level of “water–energy–food” in the Yangtze River Delta city cluster, which was first inhibited and then promoted from 2013 to 2021. The impacts of green finance on the efficiency of the three subsystems are also characterized by a “U” shape. However, linear impacts show differences, with green finance improving the efficiency of the water subsystem but not the energy and food subsystems. The implementation of China’s national strategies empowers green finance. The digital strategy, the “dual carbon” strategy, and the new urbanization strategy have increased the effectiveness of green finance in contributing to the level of water–energy–food synergy. Regional heterogeneity analysis shows that the promotion effect of green finance mainly exists in non-resource-based cities, non-main grain-producing areas, and non-cities along the South-to-North water diversion route and large cities. Finally, this paper puts forward relevant policy recommendations.

Coupling efficiency and spatial dynamic evolution of urban water–energy–food in China–A case of evidence from 94 cities

Quantifying and interpreting the water–energy–food (WEF) nexus is critical to achieve the sustainable development of urban resources. The mismatch between urban water, energy and food allocations is a prominent problem that is particularly acute in the Yellow River Basin (YRB) of China. In this study, models for the WEF coupling degree and coupling efficiency were constructed. The WEF coupling efficiencies of the 94 cities in the YRB from 2011 to 2020 were quantified using a data envelopment analysis (DEA) model. On this basis, the spatial distribution characteristics and evolutionary trends of different urban WEF coupling efficiencies were analysed and explored using an exploratory spatial data analysis (ESDA) model and a parametric kernel density estimation model. The results show that the energy subsystem constrain the development of the WEF nexus, and the food subsystem, in turn, regulates the development of the WEF nexus. In some years, the phenomenon of ‘resource curse’ occurred, in which the WEF coupling degree increased while the coupling efficiency decreased. Overall, the values of the urban WEF coupling efficiency were low, ranging from 0.5300 to 0.6300, which is not effective. Spatial clustering was detected in the urban WEF coupling efficiency. The clustering types were ‘high–high’ clustering areas in less developed regions and ‘low–low’ clustering areas in developed regions. The two clusters and the median contiguous group had different evolutionary trends. Both efficiency and polarisation increased in the high-clustering group, efficiency improved in the low-clustering group, and a new efficiency pole was formed in the median contiguous group. Among the three grouped cities, we discuss the potential of policies such as cross-city cooperation, intra-city multi-sectoral cooperation and cultivating new central growth cities to improve the WEF coupling efficiency in the YRB.

El sistema agroalimentario de la ciudad de Puebla después de la pandemia de COVID-19

This research analyzes the effects of COVID-19 pandemic in the agriculture-food system of Puebla, Mexico; considering production, supply-distribution and consumption of food subsystems. To study the contingency consequences, the case of “Central de Abastos de la Ciudad de Puebla” was selected as a wholesale market where the main players (producers, wholesalers and consumers) coexist. Qualitative method was applied representing the results of two surveys in this market, one of them in 2018, before pandemic, and the other in 2022, after health crisis. For the survey information and available statistics about food production, trade and food prices, some aspects were discovered: the negative effects of pandemic were produced by structural points of food system in neoliberal period and the resilience of agriculture system supported by rural producers city of Puebla suburbs who produced enough volume of food to supply the wholesale. This is a research focus to create a food public policy to attend the structural problems and also to mitigate the contingency effects like pandemic occurred between 2019 and 2022.

Analyzing spatio-temporal changes and trade-offs/synergies of gross ecosystem product based on water-energy-food nexus.

The value of the ecosystem's ultimate goods and services for human welfare and long-term economic and social development is known as the gross ecosystem product (GEP). For the study of GEP accounting, the suggested water-energy-food (WEF) nexus offers a fresh viewpoint. This work aims to build a GEP accounting index system based on WEF, investigate its spatio-temporal evolution characteristics, and assess trade-offs and synergies between and within the water, energy, and food subsystems. Using the Three Gorges Reservoir area (TGRA) as an illustration, the findings revealed that, firstly, the comprehensive benefit of GEP based on WEF showed an upward trend in TGRA. Still, it was worth noting that the total production of the food ecosystem decreased. Secondly, the GEP based on WEF in five periods showed a spatial pattern of "high east and west, low middle." Thirdly, the Pearson correlation coefficient indicated that the GEP trade-off relationships based on WEF were dominant in TGRA, with the strongest trade-offs between AQV, SCV, APV, and LEV. In addition, in bivariate local spatial autocorrelation, the value of the six ecosystem service function relationships was dominated by the trade-off relationship, and the distribution of trade-offs and synergies showed significant heterogeneity at the county scale in the TGRA. Finally, hot spot analysis showed that the hot spots of the gross water and energy ecosystem products were scattered in the tail area of the study area. In contrast, the hot spots of the gross food ecosystem product were concentrated in the belly region. The findings of this study provided a basis for the scientific formulation of territorial spatial pattern optimization for water, energy, and agricultural resources in the TGRA and can more accurately reflect the status of the ecological environment and changes of WEF over time. Moreover, this paper also gives full play to the growth advantages of shipping and aquatic products, implements effective soil erosion prevention and control measures, and establishes water-saving mechanisms and other measures in terms of water resources. Subregional plans for industrial structure and strengthening of waste gas and wastewater treatment facilities regarding energy resources are developed. Implement the cultivated land protection system and promote the superiority of crop varieties and other measures in terms of food resources.

A comprehensive assessment indicator of the water-energy-food nexus system based on the material consumption relationship

The input–output relationships among material, energy, and information within the water, energy, and food subsystems are intricately interwoven, constituting an integrated system vital for sustainable development. Various water-energy-food (WEF) nexus indicators have been applied to evaluate the system's internal relationships and state. Nevertheless, these methods fail to aggregate the internal relationships into an indicator. This study proposes a WEF nexus indicator that incorporates the interconsumption into the system using the material flow analysis. The interconsumption consists of energy consumption in the food and water subsystems, water consumption in the energy and food subsystems, and food consumption in the energy subsystem. Moreover, the major factors were identified by the sensitivity factor method. The three countries (Tajikistan, Uzbekistan and Turkmenistan) in the Amu Darya River (ADR) basin exhibit strong interactions in the WEF nexus system, are chosen as a case study. Our results show that in 1992–2018, Uzbekistan's food subsystem consumed the most energy among the three countries; the energy consumption within the water subsystem displays an upward trend across all three countries; the water consumption in the energy subsystem of Tajikistan and Uzbekistan is 2–4 times greater than that in Turkmenistan; and the water withdrawals for agriculture within the three countries have remained relatively stable. The composite index in three countries exhibits an upward trend, with the most pronounced increase occurring in Turkmenistan. Uzbekistan has the strongest WEF nexus relationship, with a WEF nexus index that was 2–3 times greater than that of Tajikistan and Turkmenistan. The most important subsystem of Tajikistan and Turkmenistan is the energy subsystem; however, water resources are the major factors in Uzbekistan. The introduced indicator enables a comparison of the WEF system between regions and temporal variations in a certain region. It can provide intuitive and effective data support for WEF nexus system management.

Spatio-temporal evolution pattern and obstacle factors of water-energy-food nexus coupling coordination in the Yangtze river economic belt

The water-energy-food nexus (WEF nexus) poses a substantial global challenge driven by population growth and resource scarcity, necessitating the optimization of interconnections between water, energy, and food subsystems. The effective management of the WEF nexus has emerged as a pivotal component of sustainable development strategies. Based on the Driver-Pressure-State-Impact-Response (DPSIR) framework, this research establishes a comprehensive WEF nexus assessment indicator system to scrutinize the interrelationships and coordination mechanisms among these three essential systems. This study investigates the spatio-temporal characteristics and obstacle factors within the Yangtze River Economic Belt (YREB) from 2012 to 2022 using the coupling coordination degree (CCD) model and obstacle factor diagnosis (OFD) model. The findings reveal several key insights: (1) The WEF nexus coupling degree (CD) across various provinces within the YREB currently exhibits a high-quality coupling state, characterized by minimal fluctuations and robust interconnectedness among the three subsystems; (2) Noteworthy disparities are observed in the spatio-temporal pattern of the WEF nexus CCD, reflecting an overarching evolutionary trend from low to high coupling coordination; (3) The obstacle factor analysis underscores critical areas for future focus in the YREB's development, emphasizing the efficient treatment of industrial emissions, urban water conservation, and adjustments to the proportion of coal consumption. This study contributes valuable insights for the CCD of the WEF nexus, providing valuable decision-making references for regional resource integration and the pursuit of sustainable development goals.

Development of a novel framework for agriculture simulation model for food-energy-water nexus analysis in watershed-scale

Agricultural crop production is the most vital sector of the food subsystem within the Food-Water-Energy (FEW) Nexus system, and many environmental and external factors affect it. Complex interactions between FEW subsystems and complex interrelations within each FEW subsystems affect each other dynamically. As a result, in this study, based on the dynamics between FEW subsystems and within FEW subsystems in agriculture, the Agriculture Simulation Model for the Food-Energy-Water nexus (ASM-FEW) is presented at the watershed scale. ASM-FEW includes modules for multi-crop yield modeling and calibration, energy consumption, indices related to FEW, and a comprehensive Water-Energy-Food Nexus Index (WEFNI) to assess crop production efficiency FEW Nexus approach. Modeling evaluation criteria demonstrate the precise crop yield modeling of ASM-FEW for the study area, the Maragheh-Bonab region in the Urmia Lake Basin, from 2005 to 2015. Model evaluation criteria demonstrate precise crop yield modeling. Results show that Potato and rainfed Chickpea exhibit the highest and lowest energy consumption indices, at 222,766 and 19,503 MJ/ha, respectively. Water economic productivity indices indicate irrigated Potato and Wheat as the highest and lowest, with values of 1.084 and 0.114 $/m3, respectively. Energy economic productivity indices reveal that irrigated Onion and rainfed Wheat are the highest and lowest, at 0.132 and 0.006 $/MJ, respectively. Lastly, according to the WEFNI index, irrigated Onion and irrigated Wheat are the most and least suitable crops for cultivation, with values of 0.66 and 0.264, respectively.

A review on food subsystem simulation models for the water-food-energy nexus: development perspective.

Agricultural crops are the primary food source because livestock and poultry products also indirectly depend on crops. A significant obstacle to adopting the water, food, and energy (WFE) nexus is the lack of a comprehensive and easy-to-use simulation model for the food subsystem focusing on crops. By reviewing the articles in Scopus and Google Scholar databases, WFE nexus studies can be divided into two categories: simulation-based and conceptual-based studies of WFE nexus. Based on the developmental perspective on food subsystem modeling in the WFE nexus, the conceptual studies were excluded, and the modeling studies were reviewed. Two points of view can be used for WFE nexus modeling: 1. hard-link modeling and 2. soft-link modeling. Comparing these two types of modeling showed that hard-link modeling cannot model the interrelations of the food subsystem, and this shortcoming is of great importance. This study reviewed the crop growth models (CGMs) used in the WFE nexus system from the development perspective. The technical characteristics of the CGMs have been evaluated according to the requirements of the CGMs. Finally, a checklist based on the criteria defined for the nexus system has been provided, which can guide researchers in choosing the appropriate CGMs for the food subsystem with the nexus approach. The analysis revealed that none of the CGMs studied alone were sufficient to develop a simulation model for the food subsystem with the WFE nexus. However, the AquaCrop model met more criteria.

A comprehensive energy simulation model for energy-water-food nexus system analysis: A case study of the great Karun water resources system

Focusing on the importance of energy in the Energy, Water, and Food (EWF) nexus, this study develops a comprehensive energy simulation under the EWF nexus system approach (CESNeX). The simulation model employs an effective template for planning and decision-making in the nexus system. The CESNeX simulates the energy subsystem in both the demand and supply sides as required in the nexus simulation of EWF on a river basin scale, considering nexus variables. The CESNeX evaluates the effects of various energy generation scenarios on the water subsystem by interacting with the principal nexus variables on the supply side of the energy subsystem. In the comprehensive simulation of the nexus system, the CESNeX can interact with water and food subsystems via nexus variables and provide the energy-efficient cropping pattern. The demand side of CESNeX can assist policymakers in developing an appropriate cropping pattern, considering water and energy consumption. Additionally, the supply side of CESNeX can provide the produced energy based on water consumption and the change in the reservoir head. 14 years of data (2008–2021) from the Great Karun Basin's Karun-4, Karun-3, Karun-1, Masjed Soleyman, Gotvand, and Dez reservoirs are utilized for the simulation's calibration, verification, and modelling. On the supply side, results revealed that by increasing the nexus variable of Karun-4's firm energy by about 5%, the reservoir net head is related to the Karun-3 power plant decreased by 1.93 m. Also, the largest increase in net reservoir head was related to the Karun-1 power plant, about 54 cm. There has also been a decrease of 18 MCM and an increase of 25.8 MCM in the volume of water used by the turbines at the aforementioned power plants, respectively. On the demand side, results of receiving nexus variables from the water and food subsystems showed that Potato has the highest energy consumption (150 PJ), while Barley has the lowest (20 PJ). In terms of water consumption, Potato and Barley have the highest (3.5 BCM) and lowest (1.5 BCM) water requirements, respectively. This study suggests expanding Barley cultivation in the region under consideration. Barley requires significantly less water and energy than other crops. In addition, based on the results of the CESNeX simulation model, it is recommended that less Potato be grown in this region due to its relatively higher water and energy needs.

Coupled development of the urban water-energy-food nexus: A systematic analysis of two megacities in China's Beijing-Tianjin-Hebei area

Promoting the coupled development of water, energy, and food (WEF) subsystems is a critical step to enhance synergies and increase efficiencies in the WEF nexus. However, the evolution and obstacles of coupled development are largely ignored. This study developed a framework dividing links in the nexus to select indicators and integrated models for the degree of coordination and obstacle diagnosis to explore the coupled development of the WEF nexus from 2000 to 2020 in the water-scarce megacities of Beijing and Tianjin. The results show that the average coordination degree of the WEF nexus in Beijing (0.315) and Tianjin (0.317) is at a low level, indicating a limited interaction between the WEF subsystems, while the coordinated development degree of the WEF nexus is increasing. The order degree of the WEF subsystems shows a two-level hierarchical structure, indicating that both similarities and differences are included in place-specific characteristics. Furthermore, obstacle factors are identified from water and energy subsystems, in which environmental water use (W3) and the energy consumption per gross domestic production unit (E4) played the most significant roles and require a higher priority in policy response. The results in this paper complement obstacle factor analysis in WEF nexus practice, and provide operational indicators for nexus governance.

A comprehensive evaluation of the security of the water-energy-food systems in China

Water-energy-food (WEF) are the indispensable resources for achieving sustainable social-economic development, poverty reduction, and human well-being. An appropriate WEF security evaluation may help inform China's sustainable resource production and consumption. This study selects 27 indicators representing pressure-state-response (PSR) dimensions to evaluate the WEF security of 30 provinces in mainland China from 2010 to 2019 using the entropy weight method and matter-element extension (MEE) model. The results indicate that the security of the water subsystem is mostly under high risk, and is relative severe in the Beijing-Tianjin-Hebei region, Shanghai, Shandong, and Ningxia. Meanwhile, energy subsystem indicators like carbon emission and energy intensities have significantly improved. All food subsystem indicators have improved by varying degrees. Regionally, food security is high in the east, and low in the central and western regions. In terms of the performance of PSR dimensions, “Pressure” is the most optimistic, followed by “Response” and “State”. The “Response” in most provinces is getting better, which has promoted the overall improvement of WEF systems. Thus, while maintaining the subsystem with high security, the integrated system's security can be enhanced by addressing the shortcoming of other subsystems. This can help realise synergistic resource use and enhance their security.

Coordinated analysis and evaluation of water–energy–food coupling: A case study of the Yellow River basin in Shandong Province, China

Water resources, energy, and food are important basic resources for high-quality regional development. In the process of rapid development of regional economy, how to coordinate the development of basic resources has become one of the most serious challenges to the high-quality development of the Yellow River basin and even the whole Yellow River basin in Shandong province. Previous studies have produced few such analyses and evaluations for cities in the Yellow River basin, and there is a lack of research on multi-scale analysis, evaluation and prediction of urban coupling and coordinated development level. Hence, in this study, we propose an indicator system consisting of 24 indicators for the water resources, energy, and food system based on panel data for 9 cities in the Yellow River basin in Shandong Province for 2011–2020. Spatial autocorrelation analysis and temporal and spatial distribution analysis were used to determine the current state of water resources, energy, and food systems at multiple scales; combined weighting, comprehensive evaluation, and coupling coordination quantification were used to formulate the coupling coordination relationships of water resources–energy–food and identify the spatiotemporal formation and development of the water resources–energy–food system. A particle swarm optimization–back propagation model (PSO-BP) was used to predict the coupled and coordinated changes in the water resources–energy–food system for the next five years. The study results show that: (1) The composite index of the water resources–energy–food system showed an increasing trend, and the composite index of the food subsystem increased relatively quickly. (2) In 2020, the coupling coordination degree for eight of the nine cities in the Yellow River basin in Shandong Province was 0.70. Jinan, the exception, was at a critical stage of transitioning from low to moderate coupling, and the other eight cities were at the moderate stage of coupling coordination. (3) The coupling coordination of the water resources–energy–food system is increasing; it has transitioned from low to moderate and is about to transition to the stage of good coupling coordination. (4) The PSO-BP model predicted that the coupling coordination of water resources–energy–food systems in the Yellow River basin in Shandong Province will reach the stage of good coupling coordination in 2023. The research results presented in this paper can provide a theoretical basis for formulating policy recommendations in the Yellow River basin in Shandong Province.

Urban ecosystem services supply-demand assessment from the perspective of the water-energy-food nexus

To facilitate sustainable urban development, a pressing issue is how to integrate the water-energy-food nexus (WEF-Nexus) into the assessment of supply and demand of urban ecosystem services (UESs). This study proposed a conceptual framework for the supply-demand assessment of UESs from the WEF-Nexus perspective. Taking the city of Suzhou, China, as an example, the relationships between UESs and WEF-Nexus were identified by the correlation and regression analyses based on the total supply of each urban ecosystem service and evaluation value of each subsystem of WEF-Nexus. Then the supply-demand matching of UESs was evaluated by the supply-demand matching degree and z-score standardization. The results indicated that the water and energy subsystems were positively correlated with water yield/soil retention, and negatively correlated with carbon storage/food production. The food subsystem showed significant positive correlations with carbon storage/food production. Three UESs related to WEF-Nexus, carbon storage, soil retention and food production, were always in short supply, while water yield has shifted to oversupply. The supply-demand spatial mismatches of carbon storage/food production became more pronounced, showing a trend of spreading from urban central areas to the periphery. Therefore, this study provides a scientific basis for proposing supply-demand management strategies of UESs from the WEF-Nexus perspective.

Exploring the relationship between water-energy-food nexus sustainability and multiple ecosystem services at the urban agglomeration scale

The current perception of how ecosystem services (ES) affect the water-energy-food nexus sustainability (hereafter, nexus sustainability) is still unclear. Here, we proposed an analytical framework to explore the relationship between nexus sustainability and multiple ES. This study took the Yangtze River Delta Urban Agglomeration (YRDUA) as an example. Firstly, a nexus sustainability evaluation index system was established to evaluate the sustainability of water-energy-food nexus and its three subsystems. Then various models were utilized to quantify the four ES (water yield, carbon storage, soil retention, and food production). Finally, the coupling coordination degree model and correlation analysis were applied to explore the relationship between nexus sustainability and multiple ES. The results show that the coordination between nexus sustainability and water yield gradually improved, while that between nexus sustainability and food production declined significantly, especially in the southern regions of the YRDUA. There were obvious spatial heterogeneities in the coordination between nexus sustainability and carbon storage/soil retention, characterized by a coordination state in the southern regions and an incoordination state in the northern regions. A complex relationship between nexus sustainability and multiple ES existed. Water subsystem sustainability had significant and positive linear correlations with water yield/carbon storage, and a significant and positive nonlinear correlation with soil retention. There was also a significant and positive nonlinear correlation between food subsystem sustainability and food production. The nonlinear correlations between energy subsystem sustainability and four ES were not significant in most years. Therefore, relationship-based and location-based management measures, such as ecological protection and restoration, strictest water resources management and cross-city cooperation, were proposed to facilitate the sustainable and coordinated development of nexus sustainability and multiple ES. This study can also provide references for the coordinated development of nexus sustainability and multiple ES in other urban agglomerations within and beyond China.

Energy simulation modeling for water-energy-food nexus system: a systematic review.

Since essential nexus variables were not considered in the energy subsystem, this study focused on the role of energy in the Water, Energy, and Food nexus (WEF nexus) system. The energy subsystem interacts with water and food on the supply and demand sides. The WEF nexus-based energy model has not been reviewed recently. This study provides a systematic review of 459 articles regarding energy simulation modeling issues relating to the WEF nexus system. The keyword ("energy" AND "simulation" AND "nexus") as well as "water" OR "food" OR "climate" OR "land" OR "carbon" OR "environment" is used for searching WEF nexus documents for energy simulation. The review highlighted that the energy subsystem is modeled online (One-way) and offline (Two-way), and the energy simulation struggles to represent its system boundary with the water and food subsystems in different spatial scales (household to global). The energy subsystem of the WEF nexus did not address return flow from cooling towers and crop energy consumption comprehensively. In the research, the supply and demand section of the energy subsystem demonstrated that a comprehensive simulation model for energy can be developed using the nexus system approach. The energy subsystem's supply, primarily power plants, interacts with the water subsystem, and the energy generation policy is based on water use. The WEF nexus system assesses renewable energy effects to reduce tradeoffs. In addition, energy demand is related to energy consumption, so the energy consumption for each crop can be calculated and explained the appropriate cultivation pattern based on it.

Sustainability and efficiency of water-land-energy-food nexus based on emergy-ecological footprint and data envelopment analysis: Case of an important agriculture and ecological region in Northeast China

Ecological security and efficient utilization of resources in the water-land-energy-food (WLEF) nexus are important strategic needs. Therefore, this study developed an emergy ecological footprint using the super-efficiency Slacks-Based Measure-Data Envelopment Analysis (SBM-DEA) to comprehensively evaluate the ecological security and efficiency of the WLEF nexus from 2006 to 2019 in the Songnen-Sanjiang Plain in Northeast China. Our findings indicated that: 1) Ecological security had improved from 2006 to 2019, with an average ecological carrying capacity supply and demand balance index of 3.301 and 2.723 in 2006 and 2019, respectively. 2) The average concordant index in the Songnen Plain and Sanjiang Plain was 1.258 and 1.358 respectively, indicating that the Sanjiang Plain had better ecological security than the Songnen Plain. 3) The efficiency of the water and energy subsystems demonstrated an increasing trend over time, with the overall land subsystem increasing before 2016 but decreasing afterwards. 4) The efficiency of the Songnen-Sanjiang Plain's water, land, energy, and food subsystems varied greatly on temporal and spatial scales. The water efficiency in the Songnen-Sanjiang Plain was higher in the middle and low all around. 5) From 2006 to 2019, the WLEF nexus efficiency in the Sanjiang Plain was higher than in the Songnen Plain, and in 2019, the WLEF nexus efficiency in 50% of the cities did not reach the Songnen-Sanjiang Plain production frontier. Therefore, to achieve regional sustainable development, additional efforts are required to ameliorate the ecological conditions of the middle part of the Songnen Plain and improve the resource utilization efficiency of each subsystem, especially the water resources of the WLEF nexus.

Research on the competitive and synergistic evolution of the water-energy-food system in China

Water, energy, and food are essential and strategic resources for human well-being and socio-economic development and form the water-energy-food (WEF) system with competition and synergy. The competitive and synergistic evolution model was developed to remedy the limitations in quantitatively analyzing the tradeoffs and synergies of the WEF system. Firstly, an assessment model was developed for measuring the synergy and competition of the WEF system based on the order degree of each subsystem (That is, the development degree of each subsystem) and synergy theory. Then the synergy evolution model (SEM), with the help of a logistic model and accelerated genetic algorithm (AGA) model, was developed to measure and identify the steady-state. Furthermore, an empirical study was conducted with 30 provinces in China as examples. The results indicated that the food subsystem had the highest average order degree (0.347), followed by the energy subsystem (0.305), and the water subsystem had the lowest (0.281). The degree of order of the three subsystems exhibited an upward trend in time and has differences in the spatial distribution. Also, the results showed that synergistic, restrictive, and competitive relationships exist within the WEF system. Areas with competitive and restrictive relationships are mainly located in South China and North China, respectively, within the relationship between the water and energy subsystems. The entire country showed a restrictive relationship between the water and food subsystems. The energy and food subsystems showed that the eastern regions with relationship, while the western regions with competitive and restrictive relationship. Finally, effective measures (e.g., optimize the industrial structure, continuing to implement the strategy of “storing grain in the land and technology”, and to hold the arable land minimum) are suggested to achieve the WEF system coordinated and sustainable development. We believe that the assessment model is also applicable to assess the other complex and dynamic system worldwide that involve multiple factors.