World population will reach 9 billion by 2050 and global food production will have to increase between 70% and 100% [1
]. Meeting the future food demand is a major challenge for the current food production systems, and even more doing it without compromising the environmental integrity [2
]. Converting more land into cultivation and increasing crop yields have been largely promoted as key solutions to increase food production globally [3
]. These production-oriented policies explain why global agricultural area has expanded over 11% since 1960 [5
], and cereal crop production has almost doubled [4
However, the increasing competition for land, water and energy [6
], as well the multiple impacts agriculture has on the environment, require rethinking possible approaches to face the daunting challenge of satisfying increasing food demand within a resource-constrained planet. Many of the currents efforts are placed in increasing the sustainability of food production through so-called “sustainable intensification”, which will require improving water use or nitrogen-phosphorus’ efficiency, implementing ecological-based management practices, judicious use of pesticides, and also reconverting much of the livestock production practices [4
But beyond any productivity improvements, enhancement of consumption patterns and the promotion of healthier and sustainable diets will be of major importance to achieve positive environmental effects [7
]. Recently several studies have analyzed and recognized the importance of diets in future food security and sustainability [9
]. The literature shows that larger environmental impacts originate from animal products-based diets in comparison to less meat-based and vegetarian diets [8
]. Jalava et al. [9
] compared the current global consumption patterns with diets containing low contents of animal products, and found that lower intake of animal products lead to important water savings, i.e., lower water footprint.
In the course of the last decades, several methodologies, including the water footprint assessment (WFA) [15
], and the life cycle analysis (LCA) [16
], have been developed to assess the impacts on water resources linked to food production and consumption patterns. Both approaches involve several-step process and the suitability of one over the other very much depends on the project goal. WFA is a suitable approach particularly when the overall purpose of the assessment is to identify options for water savings, reallocation and better management, and also in order to raise awareness about water issues [16
]. A WFA involves four steps: (1) definition of the scope and goals of the assessment; (2) water accounting; (3) sustainability assessment; and (4) response formulation. There is ample literature exemplifying the usefulness of WFAs [17
]. As opposed to the WFA, the LCA is more suitable when the goal is to evaluate the environmental impacts linked to different human activities, where water use is one among many different impacts that can be assessed [16
]. LCA also involves four steps: (1) definition of the goal and scope; (2) inventory; (3) impact assessment and (4) interpretation. Organizations like the FAO have adopted the LCA methodology and the associated ISO 14046 [22
], within its environmental sustainability program.
Both the WFA and the LCA rely in the use of quantitative indicators (e.g., the water footprint), although in different phases of the assessment [16
]. Several authors have compared both methodologies [16
], and applied them to different food products, such as tomato sauce [24
], tea and margarine [25
], biomass production from energy crops [26
], or broccoli [27
] to assess the advantages and disadvantages of each one.
A large number of the studies addressing the issue of diets and water impacts relied in the methodology proposed by the WFA. Vanham et al. [12
], compared the water footprint (WF) of current consumption patterns with healthier and vegetarian diets in Europe, and found that improving diets might result in reductions of the diet’s WF between 974 and 1611 L per person and day, equivalent to savings of 23%–38%. These authors also concluded that the consumption of animal products accounts for the largest share (46%) of the WF linked to the prevailing diets in Europe. Other studies comparing three European diets (current, healthy and vegetarian) across four European areas (west, north, south and east) showed that in all zones adopting healthy and vegetarian diets could lead to substantial WF reductions (up to 41%) [13
]. Similar results have been obtained in other studies comparing different diets and dietary patterns at the country [11
] and city level [29
In much of the developed world, dietary shifts are causing important health problems [8
]. This circumstance is driving national health and/or food agencies to campaign in favor of investing public funds to raise awareness among citizens about the importance of adopting healthier food habits. Countries like Spain are placing large efforts to reverse the growing obesity problems and involving different public institutions in the promotion of the Mediterranean diet [31
]. In fact the Mediterranean diet has been recognized in many countries as a key strategy to improve a population’s health with local, traditional and seasonal products [31
]. Also, it has been recognized by UNESCO as a cultural World Heritage [34
], and was selected by the UN Food Agricultural Organization (FAO) to develop a methodological approach to assess sustainability across different agro-ecological zones [35
]. In fact, the Mediterranean diet is appreciated for its lower environmental impacts in relation with other meat-based diets [32
Other countries facing serious obesity problems, like the United States of America (US), are also investing large efforts to reverse this trend [37
]. In fact, the United States Department of Agriculture (USDA) in an attempt to raise awareness among consumers has elaborated several national dietary guidelines and recommended diets [37
Yet, most of the studies published addressing the composition of diets and associated water savings are focused on making comparisons between different dietary patterns obtained from current consumption patterns of annual statistics, like the food balance sheets of FAO [39
]. Little work has been done to compare real, local or seasonal recommended diets. Comparing recommended diets, elaborated with national and traditional recipes, dishes and products, can provide insightful results about the relationship between real consumption patterns and environmental effects, and the ingredients that generate the largest water savings.
Accordingly, the main objective of this paper is to assess the WF of two contrasting and recommended food diets, i.e., the Mediterranean and American, and to evaluate the water savings of possible dietary shifts in the two countries (Spain and US). Also, we attempt to deepen in the understanding of the relationship between products origin and consumption patterns, and their influence on the total WF and the diet’s sustainability.
of the recommended Mediterranean and USDAr diets, as well as the potential shift in dietary habits, are shown in Figure 1
for Spain (a) and the US (b). The WFmenu
of USDAr diet are higher than the Mediterranean diet, irrespectively of the products’ origin (Spain or US).
In Spain, the WFdiet of the Mediterranean diet is 5276 L per person and day, but adopting a USDAr diet will increase the WFdiet nearly 29%, up to 6780 L per person and day. The majority of this increase results from the rise in green water, followed by blue water, and to a lesser extend grey water. In the US, the WFdiet of the USDAr is 5632 L per person and day. Shifting towards a Mediterranean diet (4003 L per person and day), will decrease the WFdiet by 29%. Larger savings will be achieved in terms of green water (−1392 L/person and day) and grey water. However, in this diet-shift scenario blue WF will increase by 24%.
Green WF accounted for the largest share of both WFmenu and WFdiet in the two countries. In Spain, green WF contributes to 75% of WFdiet for the Mediterranean diet and 71% for the USDAr diet. In the US, green WF accounted for 62% of WFdiet in the Mediterranean and 69% in the USDAr diet. Blue WF was the second largest fraction in WFdiet in Spain for both Mediterranean (16%) and USDAr diet (19%). On the other hand, grey WF accounted for the second largest fraction of WFdiet in the US for Mediterranean (20%) and USDAr diets (21%).
If we took into account only the blue and green WF components of WFmenu and WFdiet, in order to discern the impacts of water resources quantity, there would be water savings equivalent to 1277 L per person and day in Spain by consuming a Mediterranean diet instead of a USDAr diet. Similar values were obtained in the US for green and blue WFs, where changing from a USDAr to a Mediterranean diet will imply a net reduction of 1252 L of water per person and day.
Comparing the WFdiet in the two different countries for the same diet revealed that, while the Mediterranean diet is more efficient in terms of water consumption in all cases, adopting a Mediterranean diet in the US would deliver greater water savings (up to 24% or 1273 L per person and day in comparison with the same diet consumed in Spain). This is due to the greater water productivity of the US’s agriculture. On the other hand, USDAr diet in Spain will increase the WFdiet 20% (1148 L/person and day) in comparison with the consumption of this diet in the US.
shows the contribution of the different groups of products to the WFdiet
in Spain and US. Dairy products, oil and vegetable fats, and meat, fish and animal fats accounted for the 68% of the green component of the Mediterranean diet in Spain (up to 2662 L per person and day) (Figure 2
a). A shift towards an American diet of Spanish consumers would increase the consumption of dairy and meat, fish and animal products groups by 30% (+547 L per person and day) and therefore enlarge the green WFdiet
up to 4808 L/person and day. Legumes, cereals and potatoes, and eggs also represent a significant share of the green fraction of the WFdiet
under a Mediterranean and USDAr diet in Spain (22% and 19% respectively).
Changing the consumption patterns in the US and adopting a Mediterranean diet would deliver significant green water savings (Figure 2
a). Many of these water savings are related to lower green WF values associated to oil and vegetable fats (70% lower, 407 L/person and day less), meat and fish products (22% lower, 211 L/person and day less) and cocoa, chocolate and vanilla (93% lower, 257 L/person and day less) in the Mediterranean diet.
The share of blue WF among product groups is more evenly distributed in the case of the Mediterranean diet in Spain (Figure 2
b). On the other hand, legumes and nuts, and cereals and potatoes groups account for the 45% of the blue component of the USDAr diet (572 L/person and day). So the largest differences in terms of blue water WF among diets in Spain are due to the higher water consumption of legumes and nuts (almost six times higher, +273 L/person and day) as well as cereals and potatoes (almost five times higher, +195 L/person and day) in the USDAr diet in comparison with the Mediterranean one.
In the case of US, the Mediterranean diet has higher blue WF than USDAr diet. Legumes and nuts, oil and vegetable fats, and vegetables account for 62% of the blue component of the Mediterranean diet in the US (up to 455 L per person and day). A shift towards a Mediterranean diet of American consumers would increase the blue WF of these products groups: legumes and nuts (68% higher, +42 L/person and day), oil and vegetable fats (nearly five times higher, +166 L/person and day) and vegetables (nearly three times higher, +89 L/person and day).
Concerning grey WF (Figure 2
c) in both countries, the USDAr diet has higher values than the Mediterranean one, especially in US. Meat, fish and animal fats and dairy products account for 55% of the grey WF of the Mediterranean diet in Spain (260 L per person and day). Consuming a USDAr diet would lead to an increase of dairy products (46% higher, 70 L/person and day) and oil and vegetable fats (35 times higher, 67 L per person and day). Also, very significantly, the WF of cocoa, chocolate and vanilla group is higher and increases up to 480 times in changing to a USDAr diet (53 L/person and day).
In the case of the US, the legumes and nuts group alone accounts for almost 50% of the grey component of the USDAr diet (576 L/person and day). A change to a Mediterranean diet would afford a 35% reduction (202 L/person and day) in this product group.
The analysis of the individual products’ WF reveals that a limited number of products contribute the most to the green, blue, grey and total WFdiet
account for up to 36%–46% of the total in both countries and dietary options. Table 1
and Table 2
show the five products that contribute the most to the green, blue, grey and total WFdiet
for both diets and countries. Olive oil is the product which accounts the most to the WFdiet
of the Mediterranean diet, both in Spain and the US, as shown in Table 1
and Table 2
respectively. On the other hand, in the USDAr diet, semi-skimmed milk is the product that accrues the largest share of the WFdiet
(16%, equivalent to 1085 L per person day) in Spain (Table 1
). While in the US (Table 2
) the product that claims the largest WFdiet
is beef meat (14%, 789 L per person and day).
Most of the products that influence the most for green, blue, grey (and thus in WFdiet) for both dietary options and countries originate from only three products groups: (a) meat, fish and animal fats; (b) dairy products; and (c) oils and vegetable fats. Moreover, products from the group of legumes and nuts account for the major part of the grey WF for both diets in US.
Few studies have evaluated the WF of real recommended and daily menus, using traditional and national-local recipes and dishes with individual products analysis. As this study has shown, changing consumption patterns towards recommended diets based on a high intake of vegetables, fruits and fish would deliver significant water savings, in some cases larger than those associated to increasing efficient production. But this message is less likely to be embraced by the general public because of the lack of knowledge about the environmental impacts of current consumption patterns and in particular linked to the diets [54
]. This study demonstrates how important diets are for consumers and the environment, and supports other studies which argue that diets do matter when referring to sustainability [45
]. Also, this paper highlights the benefits linked to embracing the Mediterranean diet not just because of its potential health benefits, but also because it is a less water intensive diet. As shown, adopting a Mediterranean diet would lead to major water savings in Spain and also in the US. Therefore, our findings support the conclusion that diets based on low meat consumption could also be more environmentally sustainable in terms of water savings, contributing to address the health-environment problem [8
A further conclusion of this research is that the origin of the products also matter. More water savings can be achieved when efficient production systems coexist with sustainable consumption patterns. Further research is required to assess the sustainability of diets, e.g., through LCA impact [57
] or by conducting a sustainability WFA [15
], since the WF of diets only provides insight on the amount of water embedded in food production, regardless of the impacts such water consumption generates in the production regions.
The largest share of the WF of the two diets analyzed in this paper is always linked to green and blue water. Nevertheless, grey WF is considerably larger in the US, mainly because of larger nitrogen pollution in water resources caused in the production of legumes and nuts.
A few products have a large influence and account for the major part of the WF of a diet in both countries and dietary options. Meat, oils, vegetable fats and dairy products are the most influential and important ones. In the USDAr diet the product which accounts the most for the final WFs values is semi-skimmed milk in Spain, and beef meat in the US. Olive oil is the product which contributes the largest percentage of water footprint in the Mediterranean diet in Spain and the US. Despite olives being millennial, local and landscape-adapted trees, their high green WF values make olive oil one of the major water consuming products, even more than meat and dairy. Further research is thus required to assess the WF of the food components that influence the WF of diets the most, in order to obtain more accurate estimates.