PR | Book chapter | EPTD | IFPRI-4

PR | IFPRI4 | EPTD

A new paradigm for sustainable, integrated, water resources management is emerging from international conferences around the world. Its most succinct description is ‘the water–food–energy nexus for a green economy’. The water, food and energy nexus aims at the most efficient, best practice principles applied throughout the full food supply chain. This includes consideration of reducing wastage of the food for various reasons in the supply chain. This paper describes the global opportunities for better efficiency and resources conservation in the water, food, and energy supply chains with examples from Australia. Food wastage equates on average to 243 l day⁻¹ of water per person in the food they throw away, which is 1.5 times the daily water use per person in the UK. The concepts of virtual water and water footprint can help in identifying opportunities to save water by targeting reduction of wastage of food that has the highest virtual water content. A green economy aims at achieving optimised supply chain objectives in a manner that espouses the sustainability principle, gives due attention to environmental concerns and helps with eradication of poverty and hunger.

Hunger and thirst have distinct goals but control similar ingestive behaviors, and little is known about neural processes that are shared between these behavioral states. We identify glutamatergic neurons in the peri-locus coeruleus (periLCⱽᴳᴸᵁᵀ² neurons) as a polysynaptic convergence node from separate energy-sensitive and hydration-sensitive cell populations. We develop methods for stable hindbrain calcium imaging in free-moving mice, which show that periLCⱽᴳᴸᵁᵀ² neurons are tuned to ingestive behaviors and respond similarly to food or water consumption. PeriLCⱽᴳᴸᵁᵀ² neurons are scalably inhibited by palatability and homeostatic need during consumption. Inhibition of periLCⱽᴳᴸᵁᵀ² neurons is rewarding and increases consumption by enhancing palatability and prolonging ingestion duration. These properties comprise a double-negative feedback relationship that sustains food or water consumption without affecting food- or water-seeking. PeriLCⱽᴳᴸᵁᵀ² neurons are a hub between hunger and thirst that specifically controls motivation for food and water ingestion, which is a factor that contributes to hedonic overeating and obesity.

Holistic water management approaches are essential under future climate and socio-economic changes, especially while trying to achieve inter-disciplinary societal goals such as the Sustainable Development Goals (SDGs) of clean water, hunger eradication, clean energy and life on land. Assessing water resources within a water-food-energy-environment nexus approach enables the relationships between water-related sectors to be untangled while incorporating impacts of societal changes. We use a systems modelling approach to explore global change impacts on the nexus in the mid-21st century in a complex western Himalayan water resource system in India, considering a range of climate change and alternative socio-economic development scenarios. Results show that future socio-economic changes will have a much stronger impact on the nexus compared to climate change. Hydropower generation and environmental protection represent the major opportunities and limitations for adaptation in the studied system and should, thereby, be the focus for actions and systemic transformations in pursue of the SDGs. The emergence of scenario-specific synergies and trade-offs between nexus component indicators demonstrates the benefits that water resource systems models can make to designing better responses to the complex nexus challenges associated with future global change.

In Africa, water resources pervade multiple sustainable development goals (SDGs), which mainly focus on eliminating poverty (SDG 1) and hunger (SDG 2), promoting good health and well-being (SDG 3) and supporting clean water and sanitation (SDG 6). Africa's water scarcity problems have been worsened by population growth and climate change. Agriculture is the largest consumer of water in Africa, and a clear understanding of the water-food nexus is necessary to effectively alleviate water-related pressures on food security. Water footprint (WF) accounts and decompositions provide insights into water management planning for policy-makers. We investigated the WF of food consumption from 2000 to 2018 in 23 African countries and used the logarithmic mean Divisia index (LMDI) to decompose its driving forces into consumption structure, per capita food consumption, water intensity and population effect. The WF of food consumption increased from 609.8 km³ in 2000 to 1212.9 km³ in 2018, with an average annual growth rate of 3.7%. The population effect contributed most to this change (64.6%), followed by per capita food consumption (28.3%) and consumption structure (7.1%). Cereals (46.7%) and livestock (24.4%) were the major contributors to the increase in the total WF. Our findings highlight that controlling population growth and improving water efficiency are effective measures to relieve water-related pressures on food consumption. However, a healthy dietary structure must also be promoted because Africa's current dietary energy level is below the global average. Moreover, nine countries in the research area have an inadequate supply of dietary energy; this will inevitably drive the WF of food, as calories increase and diets change. This study is helpful for understanding the water-food nexus in Africa and provides strategies to conserve water and enhance food production.

PURPOSE: Consuming 375–500 ml of water 30 min before a meal has been shown to reduce energy intake in older, but not younger adults. This study investigated the effects of ingesting a water preload immediately pre-meal (<1 min before eating) on within-meal ad libitum energy intake in non-obese young males. METHODS: Fourteen healthy males [mean (SD) age 27 (3) years, height 1.83 (0.05) m, body weight 80.47 (9.89) kg, body fat 17.5 (4.0) %, body mass index 24.0 (2.5) kg/m²] completed a familiarisation trial and two experimental trials in randomised counterbalanced order. Subjects arrived at the laboratory overnight fasted and consumed an ad libitum porridge breakfast. Immediately prior to the meal, subjects consumed either a 568 ml (1 pint) water preload (preload trial) or no preload (control trial). Visual analogue scale questionnaires to assess hunger, fullness and satisfaction were completed before and after the meal in both trials, as well as after the water preload. RESULTS: Ad libitum energy intake was greater (P < 0.001) during control [2551 (562) kJ] than preload [1967 (454) kJ]. Ad libitum water intake was also greater (P < 0.001) during control [318 (226–975) ml] than preload [116 (0–581) ml]. The water preload increased fullness and satisfaction and decreased hunger compared to pre-trial (P < 0.001) and the control trial (P < 0.001). CONCLUSION: This study demonstrates that consumption of a 568 ml water preload immediately before a meal reduces energy intake in non-obese young males. This might therefore be an effective strategy to suppress energy intake in this population and possibly assist with weight management.