Water is life and is one of the major inputs for agriculture. Earth has a finite supply of fresh water and therefore, demands that every drop of annual rainfall should be conserved and judiciously utilized for production and postproduction agriculture to get maximum nutrients per unit of water. The concept of water productivity in agriculture is now shifting from harvest index per unit of land and water to nutrients (protein, carbohydrate, fat, etc.) produced per unit of water. This varies with food commodities and locations. For example, the total dietary energy produced by potato, maize, peanut, wheat, milk, egg and beef using one m³ of water are about 5600 kcal, 3800 kcal, 2300 kcal, 2280 kcal, 660 kcal, 520 kcal and 100 kcal, respectively. Similarly, the production of protein using one m³ of water by potato, peanut, maize, wheat, egg, milk, chicken, and beef are 150 g, 111 g, 77 g, 74 g, 41 g, 40 g, 33 g and 10 g, respectively. This paper describes the water nutrient productivity of some of the crops and livestock products and suggests as to how to provide food and nutritional security through an appropriate and balanced diet design, to the maximum number of people of the world from the limited and dwindling land, water and bio resources.

As part of a survey conducted by the Central Agricultural Office of Hungary, 67 food samples including beverages were taken from 57 food industrial and catering companies, 75% of them being small and medium-sized enterprises (SMEs). Moreover, 40% of the SMEs were micro entities. Water used for food processing was simultaneously sampled. The arsenic (As) content of solid food stuff was determined by hydride generation atomic absorption spectrometry after dry ashing. Food stuff with high water content and water samples were analyzed by inductively coupled plasma mass spectrometry. The As concentration exceeded 10μg/L in 74% of the water samples taken from SMEs. The As concentrations of samples with high water content and water used were linearly correlated. Estimated As intake from combined exposure to drinking water and food of the population was on average 40% of the daily lower limit of WHO on the benchmark dose for a 0.5% increased incidence of lung cancer (BMDL0.5) for As. Five settlements had higher As intake than the BMDL0.5. Three of these settlements are situated in Csongrád county and the distance between them is less than 55km. The maximum As intake might be 3.8μg/kg body weight.

Over the next few years, Tunisia will face a growing scarcity of water. The concept of a food consumption water footprint has been recently applied to expand knowledge about water management and to respond to problems of food insecurity. In this study, following the Water Footprint Network (WFN) method, we assessed and analysed the food consumption water footprint of Tunisian households by geographical location and by group of food products. We used results from national food surveys to collect the quantities of food consumed and the WFN database containing water footprints of food products specific to Tunisia. We found that the average water footprint for the main consumed food groups has increased by 31% during recent decades, from 1208 m³/capita/year in 1985 to 1586 m³/capita/year in 2010. Despite the decline in cereal consumption in Tunisia, the food water footprint has continued to rise as a result of increased consumption of animal source products. This increase is associated with regional variations in food choices that imply large differences in water footprints. Urban diets present higher water footprints than rural diets proportionally to higher standards of living. This study provides a new perspective on the water footprint of food consumption in Tunisia by using dietary data at the household level and demonstrated significant variability in water footprints due to different food consumption modes, and socio-economic and geographic characteristics. Future food consumption trends will likely create more pressure on water resources, especially in Tunis city and coastal areas of Tunisia. Special measures related to price policies, sensitization of consumers, and changes in production systems may have to be taken by policy makers to reduce the water footprint in order to improve food security strategies and water management in Tunisia.

The challenge of feeding nine billion people by 2050, in a context of constrained resources and growing environmental pressures posed by current food production methods on one side, and changing lifestyles and consequent shifts in dietary patterns on the other, exacerbated by the effects of climate change, has been defined as one of the biggest challenges of the 21st century. The first step to achieve food security is to find a balance between the growing demand for food, and the limited production capacity. In order to do this three main pathways have been identified: employing sustainable production methods in agriculture, changing diets, and reducing waste in all stages of the food chain. The application of an energy, water and food nexus (EWFN) approach, which takes into account the interactions and connections between these three resources, and the synergies and trade-offs that arise from the way they are managed, is a prerequisite for the correct application of these pathways. This work discusses how Life Cycle Assessment (LCA) might be applicable for creating the evidence-base to foster such desired shifts in food production and consumption patterns.

Hummingbirds are specialized nectarivores that feed on dilute solutions of sugars with trace amounts of amino acids and electrolytes. Their diets contain excess water that, if absorbed, must be eliminated. It has been hypothesized that in hummingbirds only a small fraction of this dietary water may be absorbed in the intestine. Here, we report the results of experiments designed to examine the relationship between nectar intake and water turnover in hummingbirds. Our results also allow the estimation of water absorption across the intestine and therefore test the hypothesis that ingested water in hummingbirds passes largely unabsorbed through the gastrointestinal tract. We found that fractional and total water turnover increased linearly with water ingestion. At low sucrose concentrations, food intake rates between four and five times body mass per 12 h were not unusual. A simple mass-balance model suggested that 78 % of ingested water was absorbed in the gastrointestinal tract and hence must be processed by the kidneys. However, fractional water absorption was variable and did not appear to be correlated with food or water intake parameters. Our results do not lend support to the hypothesis that the bulk of dietary water passes through the intestine unabsorbed. Although hummingbird kidneys appear well suited to excrete large volumes of dilute urine, rates of energy assimilation in hummingbirds may be constrained by excess water elimination when these birds are feeding on nectars with a low sugar concentration. | T.J. McWhorter and C. Martinez del Rio

Many modern cities have strongly invested in the sustainability of their urban water management system. Nordic cities like Stockholm or Copenhagen are amongst pioneers in investments towards integrated urban water management. However, cities can never be fully self-sufficient due to their dependency on external (water) resources. In this paper, we quantify this water dependency with respect to food consumption in nine cities located in the five Nordic countries (Sweden, Denmark, Finland, Norway and Iceland), by means of the water footprint concept. Detailed urban water footprint assessments are scarce in the literature. By analysing national nutrition surveys, we find that urban food intake behaviour differs from national food intake behaviour. In large Nordic cities people eat generally less potatoes, milk products (without cheese), meat and animal fats and they drink less coffee than outside city borders. On the other hand, they generally eat more vegetables and vegetable oils and they drink more tea and alcoholic beverages. This leads consistently – for the six large Nordic cities Stockholm, Malmö, Copenhagen, Helsinki, Oslo and Reykjavik – to slightly smaller food related urban water footprints (−2 to −6%) than national average values. We also analyse the water footprint for different diets based upon Nordic Nutrition Recommendations (NNR) for these cities. We assessed three healthy diet scenarios: 1) including meat (HEALTHY-MEAT), 2) pesco-vegetarian (HEALTHY-PESCO-VEG) and 3) vegetarian (HEALTHY-VEG). This shows that Nordic urban dwellers 1) eat too many animal products (red meat, milk and milk products) and sugar and drink too much alcohol and 2) they eat not enough vegetables, fruit and products from the group pulses, nuts and oilcrops. Their overall energy and protein intake is too high. A shift to a healthy diet with recommended energy and protein intake reduces the urban WF related to food consumption substantially. A shift to HEALTHY-MEAT results in a reduction of −9 to −24%, for HEALTHY-PESCO-VEG the reduction is −29 to −37%, for HEALTHY-VEG the reduction is −36 to −44%. In other words, Nordic urban dwellers can save a lot of water by shifting to a healthy diet.

Population growth, rapid urbanization, changing diets, and economic development are among the major driving factors of increased demand for water, food and land. In this study, an integrated model was developed for managing land-water-food nexus. A water footprint-based fuzzy fractional programming (WFFP) is developed for optimizing resource allocations toward sustainable food and water security under the agricultural, food, socioeconomic, and natural resource constraints. By calculating the blue and green water footprint of each crop, optimum food requirements were converted into optimal cropping options. The WFFP method can tackle ratio optimization problems associated with fuzzy information, in which fuzzy possibilistic programming is integrated into a linear fractional programming framework. The method is applied to a case study of the Three (Yangtze-Yellow-Lantsang) Rivers Headwaters Region of China. The results can provide the basis for water and agricultural policies formulation and land-water-food nexus management in the study region.

China’s water resources are under increasing pressure from socioeconomic development, diet shifts, and climate change. Agriculture still concentrates most of the national water withdrawal. Moreover, a spatial mismatch in water and arable land availability—with abundant agricultural land and little water resources in the north—increases water scarcity and results in virtual water transfers from drier to wetter regions through agricultural trade. We use a general equilibrium welfare model and linear programming optimization to model interprovincial food trade in China. We combine these trade flows with province-level estimates of commodities’ virtual water content to build China’s domestic and foreign virtual water trade network. We observe large variations in agricultural water-use efficiency among provinces. In addition, some provinces particularly rely on irrigation vs. rainwater. We analyze the virtual water flow patterns and the corresponding water savings. We find that this interprovincial network is highly connected and the flow distribution is relatively homogeneous. A significant share of water flows is from international imports (20%), which are dominated by soy (93%). We find that China’s domestic food trade is efficient in terms of rainwater but inefficient regarding irrigation, meaning that dry, irrigation-intensive provinces tend to export to wetter, less irrigation-intensive ones. Importantly, when incorporating foreign imports, China’s soy trade switches from an inefficient system to a particularly efficient one for saving water resources (20 km ³/y irrigation water savings, 41 km ³/y total). Finally, we identify specific provinces (e.g., Inner Mongolia) and products (e.g., corn) that show high potential for irrigation productivity improvements.

The water–climate-food security nexus is uniquely vulnerable in Central Asia, a region replete with transboundary water conflicts, shortages in land and water resources and high sensitivity to climate change. Using a water balance for the Amu Darya River Basin, we present a synthetic evaluation of future water use, crop yields, land and water productivities for the period 2016 to 2055 in Ahal, Dashoguz, Lebap, and Mary provinces in Turkmenistan. Modeled fut socio-economic scenarios include food security and diet change (FSD), export-oriented sustainable adaptation (ESA) and business as usual (BAU). Results show that water requirements and water deficits during growing seasons will exhibit a decreasing trend from 2016 to 2055 in most provinces under all three scenarios. Crop yields and land and water productivities will likely increase in the four provinces under both the FSD and ESA scenarios. Mary province had the highest mean income and losses of irrigated agriculture, with an annual average value of about 7 × 108 USD/year and 1.5 × 103 USD/year, respectively. Ahral province showed the largest annual mean land and irrigation water productivities for all three scenarios, up to about 800 USD/ha/year and 0.40 USD/m3/year respectively. Results obtained from this study provide tools to assist resource managers to identify vulnerabilities in the nexus of water, land and climate to ensure food security, water management, and sustainable development.

Seagrass meadows ecosystem engineering effects are correlated to their density (which is in turn linked to seasonal cycles) and often cannot be perceived below a given threshold level of engineer density. The density and biomass of seagrass meadows (Z. marina) together with associated macrophytes undergo substantial seasonal changes, with clear declines in winter. The present study aims to test whether the seasonal changes in the density of recovering seagrass meadows affect the benthic food webs of the southern Baltic Sea (Puck Bay). It includes meiofauna, macrofauna and fish of vegetated and unvegetated habitats in summer and winter seasons. Two levels of organization have been tested – species-specific diet preferences using stable isotopes (δ13C, δ15N) in Bayesian mixing models (MixSIAR) and the community-scale food web characteristics by means of isotopic niches (SIBER). Between-habitat differences were observed for grazers, as a greater food source diversity in species from vegetated habitats was noted in both seasons. Larger between-habitat differences in winter were documented for suspension/detritus feeders. The community-wide approach showed that the differences between the habitats were greater in winter than in summer (as indicated by the lower overlap of the respective isotope niches). Overall, the presence of seagrass meadows increased ecological stability (in terms of the range of food sources utilized by consumers) in the faunal assemblage, while invertebrates from unvegetated areas shifted their diet to cope with winter conditions. Therefore, as a more complex system, not sensitive to seasonal changes, Z. marina meadows create a stable habitat with high resilience potential.