Agricultural crop production is the largest water user worldwide. Here we compute the blue and green water consumption (WC) of global crop production at 5 arcminutes (~10 km at the equator) for the year 2020, differentiating between 46 crops, using the most recent Spatial Production Allocation Model 2020 crop data. Total crop WC amounts to 6,668 km3, or 6,817 km3 including the flooding phase of paddy rice, of which green WC amounts to 5,588 km3 and blue WC to 1,080 km3 (increasing to 1,228 km3 with paddy flooding). Over a period of 20 years, five major crops increased in total WC by 23-82%. For 2010-2020, global total crop WC increased by 9% from 6,270 km3 (with paddy flooding). Alongside observed increases in cropland area, higher crop WC puts additional pressure on limited water resources.

Annual water withdrawal for the 2534 individual power plants covering Africa.

Comprehensive but interpretable assessment of the environmental performance of diets involves choosing a set of appropriate indicators. Current knowledge and data gaps on the origin of dietary foodstuffs restrict use of indicators relying on site-specific information. This Personal View summarises commonly used indicators for assessing the environmental performance of diets, briefly outlines their benefits and drawbacks, and provides recommendations on indicator choices for actors across multiple fields involved in activities that include the environmental assessment of diets. We then provide recommendations on indicator choices for actors across multiple fields involved in activities that use environmental assessments, such as health and nutrition experts, policy makers, decision makers, and private-sector and public-sector sustainability officers. We recommend that environmental assessment of diets should include indicators for at least the five following areas: climate change, biosphere integrity, blue water consumption, novel entities, and impacts on natural resources (especially wild fish stocks), to capture important environmental trade-offs. If more indicators can be handled in the assessment, indicators to capture impacts related to land use quantity and quality and green water consumption should be used. For ambitious assessments, indicators related to biogeochemical flows, stratospheric ozone depletion, and energy use can be added.

Food systems are the largest users of land and water resources worldwide. Using a multi-model approach to track food through the global trade network, we calculated the land footprint (LF) and water footprint (WF) of food consumption in the European Union (EU). We estimated the EU LF as 140–222 Mha yr −1 and WF as 569–918 km 3 yr −1 . These amounts are 5–7% of the global LF and 6–10% of the global WF of agriculture, with the EU representing 6% of the global population. We also calculated the global LF of livestock grazing, accounting only for grass eaten, to be 1,411–1,657 Mha yr −1 , and the global LF of agriculture to be 2,809–3,014 Mha yr −1 , which is about two-thirds of what the Food and Agriculture Organization Statistics (FAOSTAT) database reports. We discuss here the different methods for calculating the LF for livestock grazing, underscoring the need for a consistent methodology when monitoring the food LF and WF reduction goals set by the EU’s Farm To Fork Strategy.

To reduce the current billions of people facing water scarcity, which is a dedicated Sustainable Development Goal (SDG) target, different actions and measures are required. This includes food labelling which accounts for water scarcity, to help consumers make informed choices when purchasing food products. The European Commission is considering the proposal of a "Sustainable food labelling framework" in the last quartal of 2023, within its ambitious Farm to Fork strategy. Implementing such a food label in the EU has a potential reach of 447 million consumers. Most prominent label candidate is its own developed PEF (Product Environmental Footprint), a tool already implemented by some retailers in the EU. However, this paper argues that the category water scarcity in the PEF has two major flaws. First, it does not account for water efficiency of a product, which is essential to solve global water stress. Second, the spatial resolution for water stress is much too coarse. The current PEF tool makes comparisons between products useless and even misleading. Its use might worsen global water scarcity, as it provides producers and consumers the wrong incentives. Urgent revision of the category water stress in the PEF is required. This can be done by using the indicators water stress and water efficiency in a complementary way, as well as using the most detailed spatial resolution science can provide.

The European Union (EU) plans to decarbonize the region by 2050. As highlighted by the Green Deal and Farm to Fork Strategy, food systems are essential for this transition. Here we investigate the resource dependence and carbon emissions of the EU-27's food systems from 2004 to 2014 via an ecological footprint (EF)-extended multi-regional input-output approach, accounting for demand and supply (including trade), and considering multiple externalities. Food contributes towards almost a third of the region's EF, and appropriates over half of its biocapacity. Average reliance on biocapacity within national borders decreased, while reliance on intra-EU biocapacity increased; yet a quarter of the biocapacity for food consumption originates from non-EU countries. Despite a reduction in both total EF and food EF over the study period, EU-27 residents demand more from nature than the region's ecosystems can regenerate-highlighting the need for new or strengthened food and trade policies to enable a transformation to sustainable EU food systems.

Global freshwater biodiversity has been decreasing rapidly, requiring the restoration and maintenance of environmental flows (EFs) in streams and rivers. EFs provide many ecosystem services that benefit humans. Reserving such EFs for aquatic ecosystems, implies less renewable water availability for direct human water use such as agriculture, industry, cities and energy. Here we show that, depending on the level of EF protection, global annual renewable water availability for humans decreases between 41 and 80% compared to when not reserving EFs. With low EF protection, currently 53 countries experience different levels of water shortage, which increases to 101 countries for high EF protection. Countries will carefully have to balance the amount of water allocated to humans and the environment.

The meaning of the LCA-developed "scarcity-weighted water footprint" or "water scarcity footprint (WSF)" was first questioned in a conceptional way by Hoekstra (2016), to which a general reply was given by Pfister et al. (2017). By means of a scientifically sound first-time detailed data analysis, Vanham and Mekonnen (2021) showed, for the case study irrigated wheat, that the WSF provides unreliable scoring, with unsustainably produced wheat better ranked than sustainably produced wheat. They show that using the WSF is counterproductive for achieving SDG target 6.4. In a letter to the editor, Pfister et al. (2022) state that "The WSF is not counterproductive to achieving SDG6" and "The WSF and water productivity are complementary approaches". They however do not provide any scientific proof for these statements. They do not base themselves on a data analysis, in contrast to the analysis of Vanham and Mekonnen (2021). To be correct, the latter statement should be "water stress and water productivity are complementary approaches", as indeed put in place in the SDG framework by means of the indicators 6.4.1 and 6.4.2. Pfister et al. (2022) also claim "Methodological shortcomings" in the analysis of Vanham and Mekonnen (2021), but these are not proven and what they list is irrelevant for the conclusions of Vanham and Mekonnen (2021). In the following text we elaborate on why the letter of Pfister et al. (2022) brings no new insights and why the analysis and conclusions of Vanham and Mekonnen (2021) are correct. The statement " The WSF is counterproductive to achieving SDG6" still holds. The way forward for the LCA framework is to use the indicator "water stress" instead of the WSF.

Background Increasing human demand for water and changes in water availability due to climate change threatens water security worldwide. Additionally, exploitation of water resources induces stress on freshwater environments, leading to biodiversity loss and reduced ecosystem services. We aimed to conduct a spatially detailed assessment of global human water stress for low to high environmental flow (EF) protection. Methods In this modelling study, we used the LISFLOOD model to generate daily natural flows without anthropogenic water use for 1980-2018. On the basis of these flows, we selected three EF methods (EF with high ecological protection [EFPROT], EF with minimum flow requirements [EFMIN], and variable monthly flow [EFVMF]) to calculate monthly EFs. We assessed monthly consumptive water use for industry, agricultural crops, livestock, municipalities, and energy production for 2010. We then estimated the corresponding number of people under water stress per month on a global and national level using a spatially detailed population database for 2010. Findings We estimate that 3.2 billion (EFPROT), 2.4 billion (EFVMF), and 2.2 billion (EFMIN) people lived under water stress for at least 1 month per year, corresponding to 46%, 35%, and 32% of the world's population in 2010, respectively. Around 80% of people living under water stress lived in Asia; in particular, India, Pakistan, and northeast China. Compared with EFMIN, imposing EFPROT globally would have put between 710 million (March) to 1 billion (June) additional people under water stress on a monthly basis, whereas this would have been 72 million (August) to 218 million (April) additional people if EFVMF were imposed. Interpretation Ensuring high ecological protection would put nearly half of the world's population (3.2 billion people) under water stress for at least 1 month per year. Policy makers and water managers have to make an important trade-off when allocating limited water resources between direct human needs and the environment. A better understanding of local ecosystem needs is crucial to alleviating current and future human water stress, while sustaining healthy ecosystems. Copyright (C) 2021 The Author(s). Published by Elsevier Ltd.

To evaluate the environmental sustainability of blue water use or the blue water footprint (WF) of a product, organisation, geographical entity or a diet, two well-established indicators are generally applied: water efficiency and blue water stress. In recent years, the Life Cycle Assessment (LCA) community has developed, used and promoted the indicator scarcity-weighted WF, which aims to grasp both blue water use and blue water stress in one indicator. This indicator is now recommended in an ISO document on water footprinting and many scholars have used associated scarcity-weighted water use indicators. However, questions on its physical meaning and its ability to correctly evaluate water sustainability have emerged. Here, we analyse for global irrigated wheat production to what extend the scarcity-weighted WF addresses blue water stress and water efficiency. We observe inconsistent results, as a significant proportion of unsustainably produced irrigated wheat has better scarcity-weighted WF scores as compared to sustainably produced irrigated wheat. Using the scarcity-weighted WF or scarcity-weighted water use for policy-making including product labelling, punishes some farmers producing their wheat in a water-sustainable way and promotes some farmers producing wheat unsustainably. Applying the scarcity-weighted WF indicator thereby is contraproductive in reaching the Sustainable Development Goal (SDG) target 6.4 on reducing water stress. In line with the specifications of this SDG target, to evaluate the sustainability of blue water use or the blue WF, the two indicators water stress and water efficiency should be used separately, in a complementary way.

The FAO Livestock Environmental Assessment and Performance (LEAP) Partnership organised a Technical Advisory Group (TAG) to develop reference guidelines on water footprinting for livestock production systems and supply chains. The mandate of the TAG was to i) provide recommendations to monitor the environmental performance of feed and livestock supply chains over time so that progress towards improvement targets can be measured, ii) be applicable for feed and water demand of small ruminants, poultry, large ruminants and pig supply chains, iii) build on, and go beyond, the existing FAO LEAP guidelines and iv) pursue alignment with relevant international standards, specifically ISO 14040 (2006)/ISO 14044 (2006), and ISO 14046 (2014). The recommended guidelines on livestock water use address both impact assessment (water scarcity footprint as defined by ISO 14046, 2014) and water productivity (water use efficiency). While most aspects of livestock water use assessment have been proposed or discussed independently elsewhere, the TAG reviewed and connected these concepts and information in relation with each other and made recommendations towards comprehensive assessment of water use in livestock production systems and supply chains. The approaches to assess the quantity of water used for livestock systems are addressed and the specific assessment methods for water productivity and water scarcity are recommended. Water productivity assessment is further advanced by its quantification and reporting with fractions of green and blue water consumed. This allows the assessment of the environmental performance related to water use of a livestock-related system by assessing potential environmental impacts of anthropogenic water consumption (only "blue water"); as well as the assessment of overall water productivity of the system (including "green" and "blue water" consumption). A consistent combination of water productivity and water scarcity footprint metrics provides a complete picture both in terms of potential productivity improvements of the water consumption as well as minimizing potential environmental impacts related to water scarcity. This process resulted for the first time in an international consensus on water use assessment, including both the life-cycle assessment community with the water scarcity footprint and the water management community with water productivity metrics. Despite the main focus on feed and livestock production systems, the outcomes of this LEAP TAG are also applicable to many other agriculture sectors.

The Mediterranean region is increasingly water scarce, with the food system being the largest driver of water use. We calculate the water resources related to food consumption in nine major Mediterranean countries, by means of the water footprint (WF), for the existing situation (period 2011-2013) as well as the Mediterranean and EAT-Lancet diets. We account for different food intake requirements according to gender and six age groups. These nine countries - Spain, France, Italy, Greece, Turkey, Egypt, Tunisia, Algeria and Morocco - represent 88% of the population of all countries bordering the Mediterranean. As first major observation, we find that the EAT-Lancet diet, a scientifically optimised diet for both nutrition and certain environmental indicators, requires less water resources than the Mediterranean diet, a culturally accepted diet within the region. In terms of water resources use, adherence to the former is thus more beneficial than adherence to the latter. As second major observation, we find that the EAT-Lancet diet reduces the current WF for all nations consistently, within the range -17% to -48%, whereas the Mediterranean diet reduces the WF of the European countries, Turkey, Egypt and Morocco within the range of -4% to -35%. For the Maghreb countries Tunisia and Algeria, the Mediterranean diet WF is slightly higher compared to the current WF and the proportions of food product groups differ. Such dietary shifts would be important parts of the solution to obtain the sustainable use of water resources in Mediterranean countries.

Arjen Y. Hoekstra, creator of the water footprint concept, unexpectedly passed away at the age of 52. He changed the way we think about water.

The rapid changes that societies have gone through in the last few decades have led to the increase in the prevalence of malnutrition in all its forms and to the degradation of natural resources and the environment. The change in the dietary habits and production systems are responsible for much of this change. Some territorial diets have been shown as potentially capable of reversing these trends by positively contributing to the health of people and the environment such as the Mediterranean Diet and the New Nordic Diet. In this paper, we review the contribution of these 2 diets to health and nutrition and to environmental, sociocultural, and economic sustainability proposing pertinent indicators. Learning from a culturally established diet and a constructed one, tradeoff could be reached to ensure better health and sustainability outcomes. Strong factors for achieving this goal lie in building on the sociocultural appropriation of diets, having the proper tools and indicators, investing in cross-sector collaboration and policy coherence, and having the necessary political support to push the agenda of sustainability forward.

Sustainable healthy diets are high on the research and policy agendas. One of the crucial resources to provide such diets are water resources. This paper provides a brief overview of the current research state regarding this topic, with a focus on the water footprint concept, as latter quantifies water use along a supply chain. The water footprint (WF) quantifies blue and green water consumption, as both these water resources are essential for food and energy production as well as for the environment. Different kinds of information are embedded in a dietary WF and different data sources and modelling approaches exist, leading to WF dietary amounts that are not always directly comparable. A full sustainability assessment of a dietary WF encompasses three components: (1) an equity assessment of the total WF amount; (2) an efficiency assessment for each food item in the diet as well as (3) an impact assessment (blue water stress and green water scarcity) for each food item in the diet. The paper concludes with an outlook on future research on the topic, listing the following points: (1) future clarity in system boundary and modelling assumptions, with comparison of results between different approaches; (2) full sustainability assessments including all three components; (3) dietary footprint family assessments with the WF as one member; (4) WF assessments for multiple dietary regimes with support to the development of local dietary guidelines and (5) assessment of the synergies with LCA-based mid-point (scarcity-weighted WF) and end-point (especially human health) indicators and evaluation of the validity and empirical significance of these two indicators

Sustainable food systems are high on the political and research agendas. One of the three pillars of sustainability is environmental sustainability. We argue that, when defining related policies, such as policies under the European Green Deal, both environmental pressures and impacts carry important and complementary information and should be used in combination. Although the environmental focus of a sustainable food system is to have a positive or neutral impact on the natural environment, addressing pressures is necessary to achieve this goal. We show this by means of the pressure water use (or water footprint) and its related impact water stress, by means of different arguments: 1) Water use and water stress are only weakly correlated; 2) water use can be evaluated towards a benchmark, addressing resource efficiency; 3) water use is used for resource allocation assessments within or between economic sectors; 4) water amounts are needed to set fair share amounts for citizens, regions, countries or on a global level 5) the pressure water use requires less data, whereas water stress assessments have more uncertainty and 6) both provide strong communication tools to citizens, including for food packaging labelling. As a result, we present a water quantity sustainability scheme, that addresses both water use and water stress, and can be used in support of food system policies, including food package labelling.

The EAT-Lancet universal healthy reference diet recommends an increase in the consumption of healthy foods, among which treenuts and groundnuts. Both are, however, water-intensive products, with a large water footprint (WF) per unit of mass and protein and already today contribute to blue water stress in different parts of the world. The envisaged massive required increase in nut production to feed a global population with this reference diet, needs to occur in a water-sustainable way. In this paper, we identify and quantify where current nut production contributes to local blue water stress and discuss options for water-sustainable nut production. We show that 74% of irrigated nuts are produced under blue water stress (of which 63% under severe water stress), throughout many regions of the world, most notably in India, China, Pakistan, the Middle East, the Mediterranean region and the USA. We critically evaluate which nut types to promote given substantial differences in WFs. We propose sustainable intensification of nut production employing nut-specific WF benchmarks. We also recommend integrated water resources management including maximum sustainable levels of water consumption by setting of WF caps.

The number of publications on environmental footprint indicators has been growing rapidly, but with limited efforts to integrate different footprints into a coherent framework. Such integration is important for comprehensive understanding of environmental issues, policy formulation and assessment of trade-offs between different environmental concerns. Here, we systematize published footprint studies and define a family of footprints that can be used for the assessment of environmental sustainability. We identify overlaps between different footprints and analyse how they relate to the nine planetary boundaries and visualize the crucial information they provide for local and planetary sustainability. In addition, we assess how the footprint family delivers on measuring progress towards Sustainable Development Goals (SDGs), considering its ability to quantify environmental pressures along the supply chain and relating them to the water-energy-food-ecosystem (WEFE) nexus and ecosystem services. We argue that the footprint family is a flexible framework where particular members can be included or excluded according to the context or area of concern. Our paper is based upon a recent workshop bringing together global leading experts on existing environmental footprint indicators.

Demand for water, energy and food, driven by a rising global population, rapid urbanization, changing diets, economic growth and climate change is increasing. A failure to balance water supply and water demand from competing sectors can trigger dangerous disparities in access to natural resources for billions of people and generate substantial economic costs. The Water-Energy-Food-Ecosystems (WEFE) Nexus is the repurposed realization that acting from the perspective of individual sectors cannot suffice to tackle the challenges facing our sustainable and secure futures. Reducing disparities and enhancing access to water services as well as energy and food is a multigoal optimization process accounting for the sectoral integration of these three key natural resources and their association to health, poverty, education and equity. Adding ecosystem services as fourth pillar of the Nexus reconciles the interests of decision makers, people and nature because it can maximize the net social benefits from the use of water ecosystems by the different economic sectors. The ultimate objective of the WEFE Nexus approach is to develop practical guidance to allow the identification of a portfolio of measures accounting for synergies and tradeoffs that are needed for the integrated achievement of the Agenda 2030 Sustainable Development Goals (SDGs). Achieving this objective calls for engaging a broad range of societal actors, improving institutional arrangements, implementing alternative technologies, and developing smart indicators for monitoring progress.