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• Causalities of 50 SDG targets in human-earth system were assessed from an expanded food-energy-water nexus. • Higher-order influence and bridging targets in the interaction network were identified. • Targets 8.4 and 6.4 can be the top priorities for future governance actions. • Targets 2.4, 13.1, 6.3, 15.1, and 15.5 were secondary priorities, with attention to trade-offs. • Implementing target 2.3 in isolation could pose systemic risks. The six Sustainable Development Goals (SDGs)—Food (2), Water (6), Energy (7), Economy (8), Climate (13), and Ecology (15)—collectively referred to as FWEECE, form the interdependent core of the human-earth system. Understanding their complex interactions is crucial for identifying transformative actions that maximize synergies and minimize trade-offs, thereby helping to rescue the 2030 Agenda. However, current research on SDG causal interactions in FWEECE remains limited. This study used structured expert elicitation to evaluate the causal interactions of 50 SDG targets in FWEECE. We applied network analysis, community detection, similarity analysis, systematic analysis, and prospective structural analysis to identify the higher-order influence, modularity, similarity, potential role, and structural function of each target within the network. Our results indicated that targets 8.4 (sustainable consumption and production) and 6.4 (increasing water-use efficiency) could be top prioritized in the global governance actions. Five targets related to food systems, water quality, climate resilience, and ecosystem protection (2.4, 13.1, 6.3, 15.1, and 15.5) were secondary priorities, while target 2.3 (increasing agricultural productivity) was considered as a high-risk. The trade-offs among food production, economic growth, and ecosystem conservation remained a major challenge for achieving FWEECE. This study provides new insights for future global priorities and is significant for promoting policy coherence and human-earth system coordination. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights • Evolution and research gaps in the FEW nexus domain are comprehensively reviewed. • The concept of nexus still lacks consistent and explicit cognition, especially for urban scale. • Three-dimensional conceptual framework for urban FEW nexus is proposed. • Future research should consider systemic optimization and increase resilience of urban system. Abstract The emerging popularity of the nexus discussion reflects the ongoing transition from a sectoral or silo approach to an integrative approach to address the global challenges pertinent to the three essential resources: food, energy, and water (FEW). Cities are critically important for advancing regional sustainable development and are thus placed at the center of the FEW nexus. This paper provides a comprehensive literature review to debate the current concepts and methods of the FEW nexus at different scales, with the aim of developing a conceptual knowledgebase framework for scientific analysis and policy making associated with the urban FEW nexus. Although the concept of nexus thinking has been widely accepted, a consistent and explicit cognition of the FEW nexus is still lacking, and a sophisticated methodological modeling framework is urgently required at various scales. As such, we proposed a three-dimensional conceptual framework of the urban FEW nexus from the perspective of resource interdependency, resource provision and system integration. This framework is useful in steering the systematic modeling and integrative management of the complex nexus issues of urban systems with different perspectives. Finally, the future directions of urban nexus research are identified from four aspects, including systematic characterization, cross-region tele-connection mechanisms, co-decision model development, and governance transition. [ABSTRACT FROM AUTHOR]

Activities in the food-energy-water nexus require ecosystem services to maintain productivity and prevent ecological degradation. This work applies techno-ecological synergy concepts in an optimization formulation to design a system for co-producing food and energy under constraints on ecological sustainability. The system includes land use activities and biomass conversion processes for the production of energy carriers, as well as supporting ecosystems that increase the supply of key ecosystem services. The co-production system was linearized and reduced to a mixed-integer linear program, which was optimized for single objectives under a variety of production and sustainability constraints. Results indicate that for the system considered to achieve high food and energy co-production, land use options should be balanced between food-producing crops and electricity-producing wind turbines and solar panels. Results also show that ecological sustainability can be achieved for this system with relatively small changes in land use patterns. The inclusion of nature in the design enables the system as a whole to achieve ecological sustainability for multiple ecosystem services with moderate sacrifices of food and energy productivity. [ABSTRACT FROM AUTHOR]

Sustainable use and management of nutrients is an important issue for food, energy and water systems. The close connections between the three systems, reflected by the “nexus” concept, warrant an integrated approach to nutrients management across the nexus. In this paper, dynamic modelling of nutrient flows in a local food-energy-water system is presented and applied to a simplified case study. The model was used to simulate several scenarios affecting nitrogen flows and stocks to assess the impact of a) the level of local wheat production, b) the selection of energy generation technology, and c) the management of available nutrient resources (digestate and straws). The simulation results showed that varying the proportion of locally produced wheat significantly affects the surface runoff and the nitrogen content in a local water body, with the latter increasing by nearly 70% in 50 years if about half of the wheat consumed is produced locally as opposed to being 100% imported. The introduction of anaerobic digestion as an energy generation option helps to supply more electricity, reduce the imported fertiliser, and also significantly reduce the landfilled nitrogen nutrient by up to 60 times, due to the reuse of the anaerobic digestate. On the other hand, a balanced consideration should be given between using the straw as fertiliser and as feedstock for energy generation. This work offers a first analysis of the food-energy-water nexus with a focus on nutrient flows and stocks. The modelling approach has the potential to inform holistic decision making with respect to nutrient usage, efficiency and the related environmental impact in the design of a local system for meeting the demand for food, energy and water. [ABSTRACT FROM AUTHOR]

• Prioritizations of the 24 targets of the five LEEW related SDGs were set. • The interactions and performances of targets were assessed to prioritize them. • Key actions for promoting these SDGs were provided (e.g., regional collaboration). • The high trade-offs among water and energy dimensions require attention. The five Sustainable Development Goals (SDGs) related to livelihood, energy, ecosystem, and water (LEEW) are highly interlinked, and their progress is a strong stepping stone to achieve other SDGs. However, research about the effective actions for promoting them in the Asian Water Tower (AWT) region (16 countries) is limited. Here, we measured the interactions (synergies and trade-offs) among and the performances of 24 SDG targets related to LEEW based on calculating correlation coefficients, network analysis, and index-based and benchmarking analysis. By aggregating the results, we eventually prioritized the 24 targets to provide evidence-based support for identifying holistic and synergistic actions across scales. Targets 2.3 (agricultural productivity), 7.1 (modern energy services), 7.2 (renewable energy), 15.2 (sustainable forests), 15.5 (habitat and biodiversity conservation), 15.6 (sharing benefits from genetic resources), and 1.a and 15.a (resources mobilization) were top-prioritized. Mainstreaming them along with numerical target values into strategies across scales can be a useful starting action. Additionally, we highlighted several obstacles for these SDGs' progress (e.g., trade-offs among basin water and energy resource management in the future energy-oriented LEEW actions) and some keys to support their achievements (e.g., interdisciplinary research, sectoral transformation, and transnational and cross-basin collaboration). [ABSTRACT FROM AUTHOR]

• An expanded food-energy-water (FEW) nexus in China is built from the lens of Sustainable Development Goals (SDGs). • China has more trade-offs than synergies in the framework of expanded FEW nexus. • Economic growth has a stronger impact on the FEW nexus than consumption and production patterns. • Changing the priorities of actions could contribute to transforming trade-offs into synergies. • Addressing the mutual inhibiting between different sectors is crucial for applying the nexus approach The nexus approach offers an important heuristic tool for the sustainable management of resources by considering the links among different sectors. The food-energy-water (FEW) nexus corresponds to links among the three of seventeen United Nations Sustainable Development Goals (SDGs), namely SDG2 (No Hungry), SDG6 (Clean Water and Sanitation), and SDG7 (Affordable and Clean Energy), and their interlinkages have a direct or indirect impact on other SDGs. However, there is still a lack of a systematic and quantitative analysis of how the nexus approach could promote achieving SDGs. Here, taking China as a case, we built an expanded FEW nexus framework from the lens of SDGs, which consists of six sectors, including food (SDG2), water (SDG6), energy (SDG7), economic (SDG8), consumption and production (SDG12), and forest (SDG15). We quantified the two-way interactions between the six sectors by the panel vector autoregressive (PVAR) model. Results indicate that sectors exhibit different response characteristics (positive or negative) in their interactions, and these responses could change over time. These results imply that changing the priorities of actions may be an effective measure to transform trade-offs into synergies. Moreover, the contribution of different sectors to each other varies considerably, with economic growth (SDG8) generally having a higher impact on changes in the FEW nexus than consumption and production patterns (SDG12). Our research suggests that strengthening the quantitative assessment of two-way interactions among the FEW nexus has crucial implications for leveraging nexus approaches effectively to achieve sustainable development for all. [Display omitted] [ABSTRACT FROM AUTHOR]

• Building-scale FEW nexus analysis can help reduce water, carbon, and ecological footprints. • System dynamics modeling is capable of simulating retrofit strategies at the building-scale. • Building information modeling can be integrated with a FEW nexus analysis. This study examines a green building retrofit plan through a system dynamics model (SDM) creating symbiosis embedded in a building-scale food-energy-water (FEW) nexus. An indicator approach was employed to exploit cross-domain seams via the use of carbon, water, and ecological footprints for sustainability, as well as food security and energy supply reliability ratio for resilience. The SDM was formulated to demonstrate a continuous stormwater treatment outflow model for rooftop farming with stormwater reuse for irrigation, nutrient cycling via the use of green sorption media, and green energy harvesting in support of rooftop farming. We prove that green energy use, stormwater reuse, and rooftop farming can lower carbon, water, and ecological footprints, avoid CO 2 emissions via carbon sequestration in rooftop farming, and improve energy supply reliability and food security. Case 1 (Base Case) includes no retrofit (current condition), Case 2 includes rooftop farming and stormwater reuse, and Case 3 incorporates additional green energy harvesting for sustaining rooftop farming. All three scenarios were assessed using a life cycle assessment (LCA) to generate water and carbon footprints. Case 3 exhibited a 2.24% reduction of total building energy demand from the utility grid due to renewable energy harvesting, while the preservation of nitrogen and phosphorus via the use of green sorption media for crop growth promoted nutrient cycling by maintaining 82% of nitrogen and 42% of phosphorus on site. The ecological footprints for the three case studies were 0.134 ha, 0.542 ha, 6.50 ha, respectively. Case 3 was selected as the best green building retrofit option through a multicriteria decision analysis. [ABSTRACT FROM AUTHOR]

• The Cape Town region is likely to face increasing water stress. • The city-level agent-based model highlights the competition among FEW sectors and assess FEW inequality. • Setting adaptive water-tariff programs could mitigate the impacts of climate change on the city and surrounding region. • We provide a testbed for policy testing and informing policy design that can be easily applied to other cities and regions. The impact of human activities and climate change occurs across a range of spatial and temporal scales, and the city or regional scale is critical for managing food–energy–water (FEW) resources. We develop a coupled human-natural system model for Cape Town, South Africa, which consists of an agent-based model and a regional hydrologic model, to study the FEW nexus connecting the agricultural, urban, and hydroelectric generation sectors. We use the model to compare three policies—a simple adaptive approach, adaptation with free water to indigent households, and water supply augmentation—and assess their ability to provide reliable FEW services to the different stakeholders under four different climate scenarios, representing moderate to severe amounts of warming. Our results indicate that Cape Town is likely to face increasing water stress as temperatures rise, and that adaptation strategies could effectively mitigate the effects of water limitations and avoid severe failures in providing FEW services across sectors. One way to manage demand for FEW services is by adjusting water price tariffs, but high prices create inequality in access to water for households with different incomes. Our analysis suggests that the water supply system in Cape Town may already be at, if not over, its sustainable capacity within the FEW nexus. Our model serves as a test-bed for assessing policies to manage stresses on water resources for the benefit of stakeholders across FEW sectors. This model can be adapted to cities and regions around the globe. [ABSTRACT FROM AUTHOR]

• Future environmental footprints of sugar crops would be underestimated without considering agricultural changes. • We integrate bio-physical GAEZ model and MRIO analysis to improve environmental footprints estimation. • We analyse the water-land tradeoffs of sugar crops under plausible irrigation expansion scenarios in LAC. Replacing traditional fossil fuel with bioethanol has been adopted in many countries to reduce carbon emissions and achieve climate mitigation targets. However, the soaring global demand for food and bioethanol in the future may impose heavy environmental pressure on major sugar crops producing regions of Latin America and the Caribbean (LAC) through significant changes in land and water uses. Irrigation expansion in the rainfed dominant cropping areas would partially slow down the land use expansion by boosting yields, but require large-scale investments. This study assesses the future land and water demand triggered by sugar crops expansion from the food-energy-water/land nexus perspective through coupling the Global Agro-Ecological Zones model (GAEZ) with Multi-Regional Input-Output (MRIO) analysis. We further analyse the tradeoffs between water and land use under future scenarios of climate change and socio-economic development regarding to the expected goals of biofuel policies and irrigation expansion strategies in LAC countries due to sufficient local water resources. The results show that the projected water and land demand of sugar crops in LAC would increase by 198% and 205% from 2014 to 2040. Increasing the low- or non- irrigated area up to 50% would mitigate the yield loss and reduce the land demand by 10%, with limited impact on the local water resources in most LAC countries. Major bioethanol producers with limited water demand compared with available water resources, such as Brazil and Argentina, could further promote irrigation to avoid significant landuse change and benefit other countries' land ecosystems via inter-regional bioethanol trade. While in potential higher water stress countries, including Dominican Republic, El Salvador, Guatemala and Mexico, under bioenergy orientated policy in 2040, reducing biofuel policy targets or importing bioethanol from resource rich countries would be a better option. These results could provide guidelines to balance sugar crops production and sustainable water and land use strategies across LAC. [Display omitted] [ABSTRACT FROM AUTHOR]

• Food-Energy water nexus was studied using a linear time variant input output model. • Food processing sector has high intersectoral resource use in the middle columbia river basin. • Agricultural crops have highest sensitivity to water and energy sectors. • System wide optimization suggested increased use of surface water and renewable electricity. With growing populations and changing climate, the food, energy and water (FEW) security have become a global issue. In response, the concept of FEW nexus in which the interdependency between FEW sectors are taken into account in order to effectively manage the resources and provide FEW security has emerged. Thus, in order to understand the interdependency between FEW sectors a thorough quantitative framework is necessary. Although there are numerous studies on FEW nexus, there is limited research on developing mathematical equations to model the FEW nexus. The goal of this study was to develop an input-output (IO) model to quantify the interdependency between FEW sectors in the Pacific Northwest. The FEW sectors were divided into 21 subsectors and IO model was used to quantify the total output of each subsector. Intensity coefficients were calculated and further broken down to technology coefficients and allocation coefficients. The uncertainty analysis was used to quantify the effect of variation in technology coefficients and allocation coefficients on output of each subsector and the results showed that these two distributions are significantly different. The results of sensitivity analysis showed that agricultural crops, especially alfalfa has the highest sensitivity to water and energy consumption due to the fact that alfalfa production is energy and water intensive. The multi-objective optimization was used to minimize the cost and environmental impact of FEW system and the results showed that in order to minimize the cost and environmental impacts, more surface water and hydroelectricity and wind electricity should be utilized. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Understanding the interconnections and tradeoffs between food, energy, and water (FEW) in grain production, which are essential for agricultural sustainability, remains an elusive yet important task. We propose a four-step analysis method for exploring potential approaches to coordinating the FEW nexus in grain production based on a conceptual framework that incorporates the impact of rural livelihood transitions and farmland resource constraints. We apply this method to a small-scale watershed in Hunan Province, China using data from land-use maps, farm household surveys, farmland quality surveys, and cropping-pattern surveys. Transitions of rural livelihoods have led farmlands to become increasingly large in scale. The combined impacts of this concentration of large-scale farms and the government subsidy policy, which favors double cropping, undermines the FEW nexus. Our findings suggest two operational approaches for coordinating the FEW nexus in rice production. One is to develop adaptive agricultural policies that support farmers whose aggregate performance on rice production is superior or more balanced. The other is to optimize cropping patterns based on the suitability of farmland for grain planting. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• The spatial pattern of the FEW nexus at the global level is measured. • Biophysical resource utilization efficiency for the FEW nexus is measured. • Biophysical indicators' independent contribution to the FEW nexus is identified. • Prior biophysical indicators for promoting the FEW nexus are suggested. Food, energy, and water are critical resources for human well-being and an essential part of Sustainable Development Goals (SDGs). The food-energy-water (FEW) nexus can create cascading effects that influence critical earth system processes. However, how to promote FEW nexus safeguarding within the planetary boundaries is still unclear. Based on global datasets of official SDG-statistics, an operating framework combined planetary boundaries and the FEW nexus was constructed. We found that although there are substantial differences in the FEW nexus performances among various countries, the overall development of three branches is coordinated. However, the massive resource consumption associated with promotion of the FEW nexus can severely transgress multiple planetary boundaries. Optimistically, if the highest efficiency is considered, the conflict between biophysical resource consumption and FEW nexus will be alleviated. Therefore, considering the utilization efficiency and independent contribution of biophysical resource, we suggest that CO 2 emissions, ecological footprint, material footprint, nitrogen, and phosphorus should be considered priorities among biophysical indicators for promoting FEW nexus within planetary boundaries. This study could be a step toward coordinating the conflicts between promoting the FEW nexus and planetary boundaries and optimizing the implementation of SDGs agenda. [ABSTRACT FROM AUTHOR]

• A hybrid inexact model is developed for the optimal management of FWE nexus system. • A MSFRP method is tailored to handle uncertainties with mixed characters. • The results can reflect the tradeoff between system benefits and risk. • Impacts of fluctuating water resource conditions on the optimal strategies are studied. • Detail managerial insights are provided for a model city (Shandong, China) in the case study. A hybrid inexact optimization model is developed for food-water-energy nexus system management with the consideration of complex uncertainties and decision makers' risk tolerance. A multi-stage stochastic fuzzy random programming (MSFRP) model is tailored to tackle variables with deeper uncertainties, a mixture of fuzzy and random fuzzy characteristics. Allowing to reflect decision makers' subjective opinion and risk preference, it can provide decision makers the tradeoff information between system benefit and risk attitude. The proposed model was applied to an agricultural area Shandong Province, China with the aim of maximum total system benefits. The valuable managerial insights on optimal cultivated land distribution, water resource allocation, and energy supply strategies are provided for decision makers under uncertainties. Meanwhile, the pesticide and fertilizer consumption for crop planting, and the carbon emission embodied in per unit crop supply are also quantitatively estimated. Moreover, by setting different water resource availability scenarios, the impacts of future water resource conditions on optimal management strategies under climate change are evaluated and discussed. The results suggested that rice would be the critical crop with the largest planting area for food security during the planning horizon. Under scarcer water resource conditions, the system benefits would reduce due to more desalination water consumption and planting strategy adjustment. However, it would lead to less carbon emission embodied in per unit crop supply and relieve local carbon emission control pressure. Compared to the conventional multi-stage stochastic programming, the developed MSFRP can be more effective to reflect the optimistic and pessimistic attitude of decision makers and deal with future scenario information with deeper uncertainties. [ABSTRACT FROM AUTHOR]

A policy and research agenda has emerged in recent years to understand the interconnected risks natural resource systems face and drive. The so-called ‘Food-Energy-Water’ (FEW) nexus has served as a focal point for the conceptual, theoretical and empirical development of this agenda. This special issue provides an opportunity to reflect on whether natural resource use, as viewed through the FEW-nexus lens, provides a useful basis for guiding integrated environmental management. Within this piece, we describe how the partiality of the FEW-nexus overlooks major pathways of resource use (i) within the food system and (ii) across the wider burden of human activity. As a result, we argue FEW-centric analysis is more likely to disguise rather than reveal key opportunities for integrated environmental management. [ABSTRACT FROM AUTHOR]