Water resources face an unparalleled confluence of pressures, with agriculture and urban growth as the most relevant human-related stressors. In this context, methodologies using a Nexus framework seem to be suitable to address these challenges. However, the urban sector has been commonly ignored in the Nexus literature. We propose a Nexus framework approach, considering the economic dimensions of the interdependencies and interconnections among agriculture (food production) and the urban sector as water users within a common basin. Then, we assess the responses of both sectors to climatic and demographic stressors. In this setting, the urban sector is represented through an economic water demand at the household level, from which economic welfare is derived. Our results show that the Nexus components here considered (food, water, and welfare) will be negatively affected under the simulated scenarios. However, when these components are decomposed to their particular elements, we found that the less water-intensive sector—the urban sector—will be better off since food production will leave significant amounts of water available. Moreover, when addressing uncertainty related to climate-induced shocks, we could identify the basin resilience threshold. Our approach shows the compatibilities and divergences between food production and the urban sector under the Nexus framework.

Socioeconomic and climatic changes and limited water resources pose various challenges to water, energy, and food sectors across the globe. The inevitable interactions between water, energy, and food systems bring about trade-offs but also synergies under different decisions and policies. To gain insights into these issues, we developed a water-energy-food (WEF) nexus model that incorporates both production (supply) and demands sides of WEF systems into a single system-of-systems model using the system dynamics (SD) approach. The model is applied to Saskatchewan, Canada, and so is named WEF-Sask. The model results reveal the various levels of sensitivities of water, energy, and food (and feed) sectors to the socioeconomic and climatic drivers. The analysis of trade-offs and synergies shows that the proposed large irrigation expansion (400%) boosts food production by 1.6% while reducing hydropower production by 2.7% in Saskatchewan. Wind energy expansion strategy (from 5% to 30% of total capacity) makes synergies that not only contribute to electricity supply but also reduce greenhouse gas emissions, industrial water demand, and groundwater use by 2.0, 5.7, and 3.8%, respectively. Biofuel use (blending mandate: 10% ethanol and 5% biodiesel) in transportation cuts GHG emissions by 1.2% but reduces the potential food export (food surplus) by 5.0%. The WEF-Sask model allows for scenario analysis toward integrated resources management, and its generic model structure can be expanded to other regions.

Agroforestry systems are widely promoted for their economic and environmental benefits. Food, energy, water and land resources in agroforestry systems are inextricably intertwined and expected to be severely impacted by climate change. Socioeconomic development and increasing populations have posed unique challenges for meeting the demand for food, energy, water and land, and the challenge will become more pressing under projected resource shortages and eco-environmental deterioration. Thus, a method of optimizing and sustainably managing the water-land-food-energy nexus in agroforestry systems under climate change must be developed.This paper develops an optimization model framework for the sustainable management of limited water-land-food-energy resources in agroforestry systems under climate change. The aims are to (1) quantify the interactions and feedbacks within water, land, food and energy subsystems; (2) provide trade-offs among water and energy utilization efficiency, economic benefits and environmental protection in agroforestry systems; and (3) generate optimal policy options among water and land resources for different crops and woodlands in different regions under different climate change patterns.The model framework is based on multiobjective fractional programming, and compromise programming is used to solve it. Climate change patterns are obtained from atmospheric circulation models and representative concentration pathways. The above aims are investigated through an actual nexus management problem in northeast China. Spatiotemporal meteorological and report-based databases, life cycle assessments, Pearson correlation analyses, data envelopment analyses and analytic hierarchy processes are integrated to realize practical application.The results show that climate variation will change the water and land allocation patterns and these changes will be more pronounced for major grain-producing areas. The optimized water allocation decreased (especially for rice, e.g., the optimal average value of the irrigation quota of rice was 4226 m³/ha, while the corresponding actual irrigation requirement of rice was [4200–7200] m³/ha) to improve the water use efficiency, and surface water allocation accounted for two-thirds. Maize had the largest planting area, although planting soybean generated the most greenhouse gases (greenhouse gas emissions from field activities for rice, maize, and soybean were 43.46%, 84.06% and 91.16%, respectively); However, these gases can be absorbed by forests. The model improved the harmonious degree of the resource-economy-environment system from 0.24 to 0.56 after optimization.Integrated models contribute to the sustainable management of water, food, energy and land resources and can consider the complex dynamics under climate change. It can be used as a general model and extended to other agroforestry systems that show inefficient agricultural production.

Population growth and climate change are likely to impact upon food and water availability over the coming decades. In this study we use an ensemble of climate simulations to project the implications of both these drivers on regional changes in food and water. This study highlights the dominant effect of population growth on per capita resource allocation over climate induced changes in our model projections. We find a strong signal for crop yield reductions due to climate change by the 2050s in the absence of CO₂ fertilisation effects. However, when these additional processes are included this trend is reversed. The impacts of climate on water resources are more uncertain. Overall, we find reductions in the global population living in water stressed conditions due to the combined effects of climate and CO₂. Africa is a key region where projected decreases in runoff and crop productivity from climate change alone are potentially reversed when CO₂ fertilisation effects are included, but this is highly uncertain. Plant physiological response to increasing atmospheric CO₂ is a major driver of the changes in crop productivity and water availability in this study; it is poorly constrained by observations and is thus a critical uncertainty.

To attain sustainable development in Latin Ameica and the Caribbean, where there is a strong dependence on commodity and food price development, priority attention towards energy, water, and food security is critical. In this literature and data analysis, we examined the baseline and trends of resource security based on the Water-Energy-Food Nexus concept. A performance index was developed to evaluate the progress in water, energy, and food security of the region, and a nexus-based index was developed to evaluate the inter-linkages of these resources. Finally, critical issues and challenges for sustainable development were addressed. Results showed that an unprecedented amount of infrastructure is needed to address increasing energy consumption. Emphasis should be placed on gradually replacing high carbon-sources that produce electricity with low carbon-energy systems and clean power production. Results also showed that water scarcity, given unequal distributions of rainfall, will be aggravated by changing climate conditions; improvements in water governance as well as water and sanitation provisions are needed. The region is a net exporter of food, at the expense of water availability and greenhouse gas emissions, and suffers from structural constraints. It is important to foster novel agricultural practices and sustainable food systems.

The usual vulnerability assessment is often sectoral and hazard-specific. With the nexus approach on water, energy and food (WEF), it is recognized that these three sectors have interactions and synergies and tradeoffs in their activities. Security has five dimensions, namely: availability, accessibility, affordability, accessibility, quality and sustainability. This study involved developing and implementing an integrated vulnerability assessment (IVA) methodology and framework of WEF security nexus applied to a watershed. The framework considered the watershed with three sub-systems of ecological, energy and food interacting with water as the common element. The same concept of vulnerability assessment was used for IVA as a function of exposure, sensitivity and adaptive capacity. IVA was operationalized by identifying variables or parameters pertaining to relationships among WEF and inclusion of sectoral variables related to the various dimensions of security. Based on the study, IVA of WEF nexus is a more holistic approach in assessing vulnerability. IVA account for the relationships among the sectors, in contrast to the sectoral approach. Using the combined climate risks due to different hazards (intense typhoons, erratic rainfall, severe drought, and temperature rise) gives a broader coverage unlike the hazard-specific approach. Parameters used were applicable for IVA of the watershed area. Additional relevant variables can be included if data are available.

Predicting food web responses to climate change can be difficult because of the potentially complex interplay between co-occurring climate variables and multiple interacting species across trophic levels. The large majority of research in this field has focused on understanding the effects of single climate variables on species at one or two trophic levels, implicitly assuming that simultaneous shifts across multiple climate variables will have additive effects on food web dynamics. We constructed a tri-trophic food web model and varied temperature, CO2, and water availability both alone and in concert to test this assumption. We found that population biomass does indeed respond additively across trophic levels when temperature, CO2, and water availability all increase simultaneously to moderate levels; however, if water availability decreases, like in a drought scenario, all three trophic levels respond antagonistically. We also found that interaction effect magnitude is highly dependent on temperature and water availability. Decreases in water availability led to 54–74% declines in population biomass across trophic levels when temperatures were within normal organismal operating ranges, but dry conditions coupled with high temperatures led to the extinction of the highest trophic level. Our results suggest that studying simplified versions of climate change and food webs will not be sufficient to predict the responses of real ecological systems. Therefore climate change ecology experiments and models must incorporate more complexity into their structure.