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Background: Climate change is increasingly affecting the supply of resources such as water and food. From 2015 to 2018, Cape Town endured its most severe drought on record. Yet, resource management often occurs in isolation, which contrasts with the holistic perspective provided by the nexus concept that recognizes the interdependence of resource sectors. This study employs system dynamics modeling, to examine the City of Cape Town's (CoCT) water-food trade-offs and interactions using qualitative and quantitative approaches. It assesses various policies proposed by the CoCT, to improve system resilience and to boost future water supplies, examining their efficacy and potential drawbacks. These policies are tested against future scenarios including population growth and climate change predictions of different severities. Results: The simulation results show an increase in food demand, which is mainly linked to population growth and a significant decrease in water availability. Without intervention, the CoCT is expected to experience serious water shortages within the 40-year simulation period. Conclusions: The findings indicate that the CoCT's strategies will effectively secure adequate water for its expanding population. However, a major concern was found to be the proposed intensification of aquifer exploitation. The model predicts that such an approach could lead to overabstraction of some aquifers, compromising their sustainability. [ABSTRACT FROM AUTHOR]

To explore the bioaccumulation of the emerging contaminants in the freshwater bodies and food crops, and the possible implications, this study investigated the chromium-enriched industrial wastewater irrigation on Lablab purpureus with respect to the physical growth, photosynthetic pigments, proline content, and antioxidant defense responses. Chromium enrichment inhibited the elongation of roots and shoots by 68% and 76% respectively, as a function of chromium concentration. The total chlorophyll, chlorophyll- a , chlorophyll- b , and total carotenoids were severely retarded by 81%, 84%, 76%, and 63%, respectively, and excessive accumulation of proline was detected at 2.80 μmol/g fresh weight. The activities of ascorbate peroxidase, guaiacol peroxidase, and catalase were significantly altered, with a strong stimulation at the chromium concentration of 0.30 mM, predicting chromium-induced toxicity of the food crop. The findings provide insight into the interference of heavy metal–contaminated wastewater irrigation practice and its alarming implications for the sustainability of food safety, the dynamic equilibrium of ecosystems, and the water–food nexus. [ABSTRACT FROM AUTHOR]

Abstract Food and water are inextricably linked. With the increase of water consumption in irrigation and food growth, water shortage has become an urgent issue. Irrational cross-regional transfer of water embodied in food exacerbates water scarcity and restrict China's sustainable development. Given that, a Virtual Water-Food Nexus Model is developed to quantify the inter-provincial transfer of water embodied in food and to identify the complicated interactions between different provinces. In detail, Environmental Input-Output Analysis is applied to quantitatively estimate the inter-provincial water transfer embodied in food trades. Based on the network constructed by interrelated nature of nexus, the mutual interactions, control situation, and the dominant and weak pathways are examined through the combination of Ecological Network Analysis and Principal Component Analysis. Two new indictors water consumption intensity and water supply capacity are first performed to measure the role of each province from the supply and consume side respectively. It is revealed that interregional food transactions failed to realize water resources dispatching management. Many water-deficient regions suffered from massive virtual water losses through food exports, but water-rich areas still import large quantities of food containing virtual water. Results show that exploitation and competition dominate the ecological relationships between provinces. Agricultural GDP ratio is the indicator which most affect water consumption intensity and water supply capacity. Network-based research contributes more insights into the recognition of water management responsibilities across provinces and municipalities. These findings will provide a scientific support to adjust unreasonable allocation of water resources in China in an attempt to addressing the contradiction between food demand and water shortages. Graphical abstract Unlabelled Image Highlights • A Virtual Water-Food Nexus Model (VWFN) from the Chinese perspective is developed. • Water consumption intensity and water supply capacity of each province are first identified. • A full picture of China's inter-provincial water transfer embodied in food trades is depicted. • China's water transfer embodied in food trades worsened the maldistribution of water resources. • Policy suggestions for various provinces are proposed based on local realities. [ABSTRACT FROM AUTHOR]

Most research into the connections between water and energy, water and food, and food and energy has been scientific and technical; little research has examined the public’s understandings of these connections. This article studies these understandings and awareness of nexus issues using a 2015 national public opinion survey on the water–energy–food nexus. Responses from this representative sample of U.S. adults are used to create “awareness measures” for elements of the nexus—water and energy, water and food, and energy and food—which are then used as independent variables to investigate the extent to which awareness is associated with support for public policies designed to address these nexus interconnections. All three measures are significantly correlated to support for policy options. Results suggest that awareness of the water–energy–food nexus may represent conditions necessary for supporting policies and that building such awareness could represent an important pathway for increasing support for policy interventions. [ABSTRACT FROM AUTHOR]

Local-scale opportunities to address challenges of the water–food nexus in the developing world need to be embraced. Borehole-garden permaculture is advocated as one such opportunity that involves the sustainable use of groundwater spilt at hand-pump operated borehole supplies that is otherwise wasted. Spilt water may also pose health risks when accumulating as a stagnant pond. Rural village community use of this grey-water in permaculture projects to irrigate borehole gardens is proposed to primarily provide economic benefit whereby garden-produce revenue helps fund borehole water-point maintenance. Water-supply sustainability, increased food/nutrition security, health protection from malaria, and business opportunity benefits may also arise. Our goal has been to develop an, experience-based, framework for delivery of sustainable borehole-garden permaculture and associated benefits. This is based upon data collection and permaculture implementation across the rural Chikwawa District of Malawi during 2009–17. We use, stakeholder interviews to identify issues influencing uptake, gathering of stagnant pond occurrence data to estimate amelioration opportunity, quantification of permaculture profitability to validate economic potential, and critical assessment of recent permaculture uptake to identify continuing problems. Permaculture was implemented at 123 sites representing 6% of District water points, rising to 26% local area coverage. Most implementations were at, or near, newly drilled community-supply boreholes; hence, amelioration of prevalent stagnant ponds elsewhere remains a concern. The envisaged benefits of permaculture were manifest and early data affirm projected garden profitability and spin-off benefits of water-point banking and community micro-loan access. However, a diversity of technical, economic, social and governance issues were found to influence uptake and performance. Example issues include greater need for improved bespoke garden design input, on-going project performance assessment, and coordinated involvement of multi-sector governmental-development bodies to underpin the integrated natural-resource management required. The developed framework aims to manage the identified issues and requires the concerted action of all stakeholders. Based on the probable ubiquity of underlying issues, the framework is expected to be generalizable to the wider developing world. However, this particular application of permaculture represents a fraction of its greater potential opportunity for rural communities that should be explored. [ABSTRACT FROM AUTHOR]

• The physical water in watershed was connected to virtual water flow as new transboundary water management. • The urban area as food consumers could be considered as main stakeholder of water management in rural area. • Physical-virtual water flow was highly influenced by the self-supply of local food. This study aimed to analyze the interaction among watershed, food-producing, and food-demanding areas through the connected system of physical-virtual water flows and local food networks in terms of the transboundary water-food nexus, even though they might not be geographically connected. Here, we analyzed the potential food network of local rice among 47 prefectures in Japan using the gravity model and estimated the physical-virtual water flows (PVWFs) by lining the physical water flow in food-producing areas and virtual water flow embedded in the food network. Through in-and out-degree centralities of the food network, we found that the results of degree centrality revealed which prefecture was more influenced by the changes in self-supply ratios (SSRs) of local rice. As all prefectures intended to increase consumption of local rice that was produced in their area, the scale of the food network was reduced, as shown by the decrease in in-and out-degree centralities. Based on the food network, we analyzed the dependency of food-demanding areas on each watershed based on a connected system of PVWFs. In a case study of the Kansai region, the northern watershed directly affected Hyogo, which was also indirectly influenced by Osaka in terms of PVWFs. In the food network with 20% SSR, the PVWF was estimated to be 189.17 × 106 m3·yr−1 from the northern watershed to Osaka in the food-producing area of the northern watershed, showing higher interaction of Osaka with the northern watershed than with other watersheds. [ABSTRACT FROM AUTHOR]

Enhancing local production is key to promoting food security, especially in rural households of low-income countries, but may conflict with limited natural resources and ecosystems preservation. We propose a framework integrating the water-food nexus and a sustainable livelihoods perspective to assess small-scale food production in water-poor regions. We demonstrate it by assessing alternative production scenarios in the Gaza Strip at different spatial scales. At the scale of a single farm, there is a clear conflict among objectives: while cash crops ensure good incomes but contribute scarcely to domestic protein supply, crops performing well from the nutritional and environmental viewpoint are among the worst from the economic one. At the regional scale, domestic production might cover an important fraction of nutritional needs while contributing to household income, but water scarcity impairs the satisfaction of food demand by domestic production alone. Pursuing food security under multiple constraints thus requires a holistic perspective: we discuss how a multidimensional approach can promote the engagement of different stakeholders and allow the exploration of trade-offs between food security, sustainable exploitation of natural resources and economic viability. [ABSTRACT FROM AUTHOR]

Global waterbodies are experiencing increased risk of eutrophication and harmful algal blooms due to excess nutrients including phosphorus and nitrogen discharged from human activity on the landscape and as a result of climate change. Despite modeling that suggests the efficacy of best management practices in agricultural systems to be sufficient to address the problem, adoption by farmers remains far below the levels needed to achieve significant water quality improvements and new approaches to encourage and sustain adoption are urgently needed. In this work, we apply a modified transtheoretical model (TTM) of behavior change to a longitudinal dataset (N = 584) of farmers' adoption decisions and stated intentions to use cover crops, collected in the Maumee Basin of Lake Erie, USA in 2016 and 2018. The TTM posits that behavior changes over time and is influenced by different social-psychological processes at each stage of change. Our findings confirm past research into the importance of many of the factors investigated, while providing new insight into their role in specific stages of the change process with potential implications for the design of interventions for farmers in different stages. Several factors investigated (mean environmental concern, education, information from conservation groups and off-farm income) were uniquely important to a particular stage. Other factors (response efficacy at the field level, total farm size and risks of spring planting interference) were important at both an earlier and later stage, but less important in predicting middle stages of change. A third set of factors (self-efficacy, proportion rented, no-till adoption and uncertain long-term paybacks) were statistically important across each stage of the TTM model. In applying the TTM longitudinally, we found evidence that farmers in a more advanced stage of cover crop adoption, in the first wave of data collection (2016) were more likely to have adopted cover crops in the second wave (2018), a result not predicted by individual factors alone. We report findings for cover crops but see the potential for the transtheoretical model of behavior change to be applied to other best management practice adoption decisions and to diverse populations of farmers to generate similarly novel insight and utility for intervention design and targeting. • Behavior change takes place over time and is a multi-stage process. • We investigate farmer adoption of cover crops, a water quality best management practice. • Farmers in different stages have different characteristics and barriers to adoption. • Farmers in later stages of change are more likely to adopt cover crops. • Interventions must target farmers' stage of change for sustained adoption. [ABSTRACT FROM AUTHOR]

In face of the interdependencies between policy areas in the management of common pool resources, studying nexus challenges is insightful for the exploration of new governance strategies. This includes the co-occurrence of and the interaction between different governance modes. We put forward the argument that a promising approach to explore these dynamics over time is the method of discourse network analysis. By conducting a discourse network analysis of German agricultural and water policy in a region with intensive livestock farming and large surpluses of manure that exert pressure on water and soil resources, we analyse the development of discourses within and across policy areas. We show that the analysis of public discourses contributes to the understanding of coordination between actors. • The separation of policy areas presents a major challenge to the sustainable management of common pool resources. • The analysis of public discourses enables a new perspective on governance types beyond the trichotomy of cooperation, competition and coercion. • Hybrid governance strategies going beyond the analytical distinction between government, market and community have proven successful for sustainable environmental management. • External pressure leads to the rapprochement of discourse coalitions. [ABSTRACT FROM AUTHOR]

• The agricultural water consumption is identified to have the most significant effect on reducing the lake volume. • A Monte Carlo system dynamics model is developed to evaluate different restoration policies for the Urmia Lake. • The novel prey predator model is developed to simulate the nexus between food security and environmental. • The lake could be restored if the all four scenarios are implemented together. In recent decades, population growth, agricultural development and climate change have caused environmental problems in the world, especially in the arid and semi-arid regions such as Iran. Urmia Lake, one of the unique biosphere reserves of the world, has suffered from these problems in the last 20 years. Although many studies conducted to the negative impacts of human-induced activities, especially agricultural expansion on the lake, few studies focused on providing restoration plans for that. This study uses a system dynamics method for modelling the restorations scenarios of Urmia Lake based on the prey-predator approach. This method is helpful to simplify the complicated feedbacks and interactions among human-environment. The Monte Carlo simulation is used to explore the effect of uncertain parameters on the lake level. Based on the results of this study, the agricultural water consumption (as predator) has the most significant effect on reducing the lake volume (prey). The results indicated that decreasing the area of irrigated lands by 40%, improving irrigation efficiency, reducing the lake area itself, and inter-basin water transfer will lead to increase in the lake water level by 2.54 m, 2.04 m, 1.19 m and 1.19 m, respectively. By applying all the suggested scenarios, the lake water level will reach to its ecological level (1274 MSL) in 2023. The recent positive restoration signals of the lake have coincidence with the findings of current research and bring more hope to the future of the lake. [ABSTRACT FROM AUTHOR]

Successful adaptation to global climate change and enhancement of agricultural watersheds' resilience requires widespread use of Nutrient Best Management Practices (NBMPs) by farms of all sizes. In the US, adoption of many NBMP practices is voluntary and insufficient to achieve local and downstream conservation objectives. Despite evidence that both social-psychological factors and socio-economic factors influence farmer decision-making, very few studies of farmers' decision-making related to NBMP adoption combine these two factor groups in a theoretically rigorous way. To better understand farmers' management decisions, we test the social-psychological Theory of Planned Behavior (TPB) to determine the relative influence of attitudes, perceived social norms, and perceived behavioral control on adoption of nine NBMPs. A survey was designed by the research team and implemented by the U.S. Department of Agriculture-National Agricultural Statistics Service (USDA-NASS) in 2013, and replicated in 2016, on a stratified sample of 129 farmers (including panel data on 56 farmers). Farmers were located in the Missisquoi, and Lamoille River watersheds of the Lake Champlain Basin in the Northeast region of the United States. Survey responses revealed variation in past adoption of NBMPs was sensitive to practice type and farm size. We developed nine weighted structural equation models to test endogenous (social-psychological) and exogenous (policy, economic and demographic) predictors of farmer intention to adopt NBMPs. We found that perceived behavioral control had the largest effect size and strongest statistical significance on the farmers' expressed intentions to adopt NBMPs in the future. For a subset of NBMPs, perceived social norms and farmer attitudes toward these NBMPs were each also significant drivers of intention to adopt individual practices. Among the exogenous variables, we found that large farm size, college education, and having a conservation easement all had a positive influence on farmers' intention to adopt NBMPs. This study suggests that for widespread adoption of NBMPs, environmental managers, policy makers, and program developers should be attentive to farmers' perceived behavioral control, and support the design and execution of outreach and technical assistance programs that build on drivers of farmers' decision making. • Self-assessed ability to adopt new practices is most important for all practices. • Previous land conservation action significant indicator of self-assessed ability. • Higher intent to adopt nutrient best practices with large farm and college education. • Programs to encourage adoption should include human behavior and demographic insights. [ABSTRACT FROM AUTHOR]

International agricultural trade triggers inter-dependency among distant countries, not only in economic terms but also under an environmental perspective. Agricultural trade has been shown to drive environmental threats pertaining to biodiversity loss and depletion and pollution of freshwater resources. Meanwhile, trade can also encourage production where it is most efficient, hence minimizing the use of natural resources required by agriculture. In this study, we provide a country-level assessment of the future international trade for 6 primary crops and 3 animal products composing 70% of the human diet caloric content. We set up four variegate socio-economic scenarios with different level of economic developments, diets habits, population growth dynamics, and levels of market liberalization. Results show that the demand of agricultural goods and the correspondent trade flow will increase with respect to current levels by 10–50% and 74–178% by 2050, respectively. The largest increase in the amount of traded goods is expected under the Economic Optimism scenario that will see an average trade flow of 2830 kcal/cap/day (i.e., nearly doubling the current per-capita flow). Most of the increase will be driven by the trade of crops for animal feeding, particularly maize will be the most traded crop. The trade networks architecture in 2050 and 2080 will be very different from the one we actually know, with a clear shift of the trade pole from the Western toward the Eastern economies. The dramatic changes of global food-sources and trade patterns will jeopardize the water resources of new regions while exacerbating the pressure in those areas that will continue serving food also in the future. In spite of this, trade may annually save around 40–60 m3 of water per person, compared to a situation where countries are self-sufficient. Unlabelled Image • There will be a transition of the food trade core from Western toward Eastern economies by 2050. • Half of the future projected agricultural demand will be met by international trade. • International trade will save 40–60 m3 of water per person, despite an increase of the total trade flow. • Increased market openness may enlarge impacts on water sources by 3 times with respect to 2016 levels. [ABSTRACT FROM AUTHOR]