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Overview

Water, food, and energy security:scrambling for resources orsolutions?Debra Perrone1,2,3∗ and George M. Hornberger1,2,3

Anthropogenic-induced climate changes and population growth projected by2050, combined with global economic growth driven by emerging markets, suggestthat greater stress will be placed on water, food, and energy resources in thefuture. These resources are interdependent and are linked in a complex globalnetwork of trade. As pressures on the three resources grow, three-way interactionsarise so that a solution to address scarcity in one cannot be achieved withoutimpact on the others. The water security, food security, and energy securitytrilemma creates a multidimensional web that is a structurally complex networkwith dynamic links among resources that vary in both weight and direction.Because structure affects function, characterizing the network anatomy thatlinks the resources in three-way interactions is helpful when setting goals tomeet resource security. We argue that water plays a central role in shapinginteractions and that the main scarcity issues occur with trade-offs betweenthermoelectric power generation and agriculture, between hydroelectric powergeneration and agriculture, and between biofuel production and food production.Three illustrations—the Apalachicola–Chattahoochee–Flint River Basin in thesoutheastern United States, the island nation of Sri Lanka, and Brazil—capture themain three-way interactions that we have identified. Although the problems thatstrew the path to global sustainability are massive, we suggest alternatives alongboth technological and nontechnological paths to meet future needs. © 2013 WileyPeriodicals, Inc.

How to cite this article:WIREs Water 2014, 1:49–68. doi: 10.1002/wat2.1004

INTRODUCTION

There has been much noise made in recent yearsabout water security, food security, and energy

security. These terms do not carry precise definitionsand, in fact, often mean different things to differentpeople. Water security carries connotations of anadequate supply of clean fresh water to support

∗Correspondence to: [email protected] of Civil and Environmental Engineering, VanderbiltUniversity, Nashville, TN, USA2Department of Earth and Environmental Sciences, VanderbiltUniversity, Nashville, TN, USA3Vanderbilt Institute for Energy and Environment, VanderbiltUniversity, Nashville, TN, USAConflict of interest: The authors have declared no conflicts ofinterest for this article.

humans, including an assessment of the risks offailure.1 Recent work on securing resources hasshown the value in successfully integrating cultural,political, and behavioral norms with technologicaland physical solutions,2 but there is no commonlyaccepted definition.3 Food security, in the context ofglobal policy issues, is defined as ‘a situation thatexists when all people at all times have physical,social, and economic access to sufficient, safe, andnutritious food to meet dietary needs and foodpreferences for an active and healthy life.4 Energysecurity is perhaps the most complicated idea ofthe three. Broadly speaking, energy security refersto the ideal of providing adequate and affordableenergy to human populations. Climate change addsan element of uncertainty to energy security; failureto account for the environment has the potential to

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Overview wires.wiley.com/water

result in large economic and social costs,5 as wellas environmental costs. Thus, the details of how tocharacterize energy security are far from trivial.6 Withthe global population expected to reach 9 billion bythe middle of this century, it has become obvious thatthe interdependencies among water, food, and energymust be considered when assessing security issues.

Recent increases in demand for water, food, andenergy highlight the complex network threading theseresources together and expose resource insecurities. Inexploring water–food–energy networks it is importantto capture the dynamics of the resources and howeach of the resources links to the others. Two-wayinteractions between resources are well establishedand intuitive. Water is withdrawn and consumedthroughout the life cycle of most primary andsecondary energy sources.7,8 Energy is consumedfor acquisition, distribution, and end-use of waterresources.9,10 Water in streams and in groundwateraquifers (blue water) and rainfall that sustains cropsand terrestrial ecosystems (green water) are vital insustaining agricultural yields. Energy is a fundamentalinput for increasing crop yields and maintaining foodsecurity.11,12 These two-way interactions help us tounderstand the links between resources, but they donot explain how the resources interact to affect thesecurity of resources. For instance, water securityis influenced both by its two-way interactions withenergy and its two-way interactions with food.

The water security, food security, and energysecurity trilemma creates a multidimensional webthat is a structurally complex network with dynamiclinks among resources that vary in both weight anddirection. Anthropogenic-induced climate changesand population growth projected by 2050, combinedwith global economic growth driven by emergingmarkets,13 suggest that greater stress will be placed onwater, food, and energy resources. Equally important,but often overlooked, political opposition and social,behavioral, and cultural norms can limit access toresources, playing an important role in securingresources. The dynamic links are influenced byexternal factors, such as stressors (e.g., growth)and limiters (e.g., norms, spatial and temporaldistribution).

In times when resources are abundant andreliable (i.e., secure), the interrelationships (i.e.,links) among water, food, and energy are definedclearly. The three-way interactions among resourcesare often overlooked; two-way interactions appearto be independent of the third resource becausethe third resource does not directly influence thefunction of the network. As resources encounterstressors and limiters, the links between them become

intertwined—affecting function—and it becomesobvious that all three resources are codependent(Figure 1). Because structure affects function,14

characterizing the network anatomy that links water,food, and energy three-way interactions is helpfulwhen setting goals to meet resource security.

In this article, we explore three-way interactionsthat affect water security, food security, and energysecurity. Two-way interactions are important, and wedo not dismiss their place in resource management,but in our article we focus on three primary waysof water–food–energy interactions: water securityfor public supply and its competition with theagricultural and thermoelectric sectors; food securityand its competition for water with the hydroelectricsector; and achieving energy security through thedevelopment of biofuels and its competition for waterand land with food resources. We acknowledge thatthere are many other interactions that influence water,food, and energy security, but we are most interestedin exploring water’s role in the intersection amongthese three resources and understanding the trade-offsinvolved in meeting water, food, and energy securitygoals. Therefore, we begin this overview by framingwater, food, and energy security in the context of thecomplex network that links the resources together. Wethen explore water’s role in the network; three casestudies are used to help illustrate this theme. Finally,we conclude the article with opportunities to managebetter water, food, and energy resources.

RESOURCE SECURITY AND NETWORKFUNCTION

Water SecurityWater security (Figure 1(a)) has two components—quantity and quality—both influencing its interactionswith food (Figure 1(b) and (c)) and energy (Figure 1(h)and (i)). Water is needed for a variety of humanand ecosystem purposes, including growing foodcrops and producing energy. Estimates of blue waterwithdrawals and consumption, although fraughtwith uncertainty because of a paucity of availablemeasurements, indicate that large quantities of waterare required for energy and for agriculture15–18

(Table 1). Globally, about 70% of freshwaterwithdrawals are used for agriculture13,19 and almost10% are used for energy13; water consumption byirrigation is one third of all blue water withdrawnglobally.20

Demand for water from both sectors is expectedto increase with population and economic growth.Urban environments are home to more than half of

50 © 2013 Wiley Per iodica ls, Inc. Volume 1, January/February 2014

WIREs Water Water, food, and energy security

FIGURE 1 | Water–food–energy interactions: (a) water resources, (b) water contamination from agricultural residue runoff, (c) blue and greenwater for irrigation, (d) food resources, (e) energy for fertilizers, pesticides, and farming equipment and machines, (f) agricultural land and resourcesfor biofuels, (g) energy resources, (h) water for fuel cycle, electricity generation, and inland transportation of energy, (i) energy for acquisition,conveyance, treatment, and end-use of water, and water contamination from energy, (j) competition-driven interrelationships, trade-offs, andinsecurities among (a) water, (d) food, and (g) energy. In times when resources are abundant and reliable (i.e., secure), the links among water, food,and energy are defined clearly. The three-way interactions among resources are often overlooked; two-way interactions [e.g., (h) water for energy]appear to be independent of the third resource because the third resource does not directly influence the function of the network. As resourcesencounter stressors (e.g., economic growth, population growth, weather, and climate) and limiters (e.g., political opposition; social, behavioral, andcultural norms; and spatial and temporal distribution), the links between them become intertwined and it becomes obvious that all three resourcesare codependent (j).

TABLE 1 Global Blue Water Use (km3/year) for Energy and forAgriculture

Water for Energy Water for Agriculture

Blue Water

Use

Thermo-

electric

Hydro-

power Biofuels Food CropsWithdrawal 5681 — 442 29003

Consumption 251 501 162 12003

Water use for energy sector activities not shown are much smaller inmagnitude than those included.1Median values reported.18 Refer to notes b and c for nuances associatedwith water requirements for thermoelectric power and hydropower.2Consumption was calculated assuming the same fractional value as thatreported for all irrigated agriculture. Although direct use of biomass dwarfsbiofuels16 and water consumption is correspondingly large, we assume thatbiomass for burning is not irrigated and therefore is not part of a blue wateraccounting. Data from Ref 16.3Data from Ref 17.

the world’s population, and this fraction is likelyto grow.13 Industrialization and urbanization arelikely to change resource demand patterns. In theUnited States, for instance, agricultural withdrawals(∼35%) rank second to the thermoelectric sector

(∼50%), and the public sector accounts for over10% of withdrawals.21 Urbanization can increasedomestic water withdrawals and consumption, as wellas wastewater, even with efficiency gains.

Food and energy resources affect the quality ofwater resources, and the quality of water resourcesaffect food and energy production. Fertilizer andbiocide residues in runoff from agricultural fields cancause hypoxia and contaminate surface water andgroundwater, respectively;22 feedlot runoff increasesmicrobiological risks.23 Poor cropland managementcan result in high soil erosion rates, leading tosedimentation and high turbidity in surface waters.24

Drilling for oil and gas wells produces contaminatedgroundwater if not treated properly, and coal miningcan lead to acid drainage if not managed properly.Thermoelectric plants can, during low flows, ther-mally pollute rivers.25 Water quality also affects thequality of food and the efficiency of energy produc-tion. Furthermore, water contaminated with organicand inorganic trace elements may require treatmentprior to use, and this treatment requires energy.



Food SecurityGlobal food resources are highly dependent on waterand energy inputs (Figure 1(c)–(e)). Irrigation, fertil-izers, and biocides, powered mechanical farm equip-ment, land-crop intensification, improved germplasmand genetically modified organisms, and landless live-stock farming all have contributed to increased yieldsover the past three centuries.26,27 Intensification ofcrop and livestock production has spared expansionof agricultural land, but ecosystems are affected fromthe concentrated outputs from food systems (i.e., non-point pollution).27 Thus, there is a an additionalfeedback relating water, food, and energy: blue andgreen water are needed to maintain crop and livestockproduction, and fertilizer, biocide, sediment, and col-iform residues from crop and livestock productiondetrimentally impact water quality, thus necessitatingadditional energy to treat the water.

As a result of increased growth in population,income, and urbanization, food demand is projectedto double in the next 50 years. In emerging marketsdiets and the overall quality of life will change withaffluence.13 Food waste is a serious concern and,unfortunately, is most prevalent on a per capita basisin developed countries.28 As wealth increases, dietswill diversify and demand will increase for processedfood, meat, and dairy. Over the past three decades,consumption patterns in Asia have moved away fromcereals and toward animal protein.29 Diversifyingfood portfolios to incorporate more livestock andless cereal is both water and energy intensive.30 Forexample, between the 1960s and early 2000s, China’sper capita water requirement for food productionincreased by a factor of 3.4 as a result of increasedmeat consumption.31 Globally, the agricultural sectoraccounts for 22% of greenhouse gas emissions, andnearly 80% of these emissions are attributed tolivestock production.26 Growth in food demand,combined with stress from anthropogenic climatechange, will intensify competition for both water andenergy resources.

Energy SecurityAs developed countries work to maintain energysecurity, but shift toward a low-carbon energy future,demand for biofuels is growing.32 Mandates in theUnited States (US) and European Union (EU) havedriven production of biofuels.33 The EU BiofuelsDirective requires member countries to realize a10% share by biofuels in the liquid fuels marketby 2020, and the US Renewable Fuel Standard callsfor production of 26 billion gallons of biofuels by2022, with 21 billion gallons from second-generation

(cellulosic) processes.a Despite the mandates and theincreased production of biofuels over the past decade,the generally accepted view is that biofuels may havea limited place in the world, and that care needs to betaken to avoid impacts on water and food.32,34 Thus,the use of biofuels to achieve energy security lendsitself to a three-way interaction among energy, food,and water (Figure 1(f)–(h)).

The importance of biofuels for energy securityand for reducing emissions of greenhouse gasseshas been debated.32,35,36 In theory, biofuels canbe produced with lower life cycle greenhouse gasemissions than fossil fuels and with little competitionto food production,37 but the current generation ofbiofuels requires significant land, water, and energyresources22,32 and can even result in large carbondebts.36 In a global context, there is reason to questionwhether growth in the biofuels market can occurwithout resulting in food shortages over the nextseveral decades.38 Although land resources may alsobecome scarce in the future,39 the main way thatstress manifests itself in the current energy securitydiscussion is through water.40

The water footprint of transportation couldincrease by a factor of 10 by 2030.41 Biofuel impactson water resources include both quantity and qualityof water.22,42 Energy is needed to pump groundwaterand power large-scale irrigation systems, and wateris needed to produce the energy for these processes.Fertilizers increase the productivity of plants used forbiofuels, but fertilizers are energy intensive and cancontaminate groundwater and surface water.39,43,44

Thus, the requirements of water for biofuels mayadd significantly to the already vexed issue ofproviding food for a growing global population whilemaintaining water of adequate quantity and qualityto preserve ecosystem services.45 The impacts ofland conversion must also be weighed, in terms ofgreenhouse gas emissions as well as displacement ofarable land away from food production.46,47

WATER’S ROLE IN THREE-WAYINTERACTIONS

We argue that water scarcity typically is the proximatecause of competition in the water–food–energysecurity arena. Increasing nonagricultural demandson water, growing food demands, changing foodpreferences, and demands for biofuels all placeincreasing pressure on water resources.12

Economic policy makers have acknowledgedthat water resources, and adequate management ofthese resources, play a vital role in national economiesbut are largely unaccounted for in planning.48



2500000Apalachicola Chattahoochee Flint

2000000

1500000

1000000

500000

0Public Domestic Industrial

Demand-side sectors

Agricultural Thermoelectric

Fre

shw

ater

with

draw

als,

m3 /

d

FIGURE 2 | Water withdrawals51 (y-axis) by demand-side sector (x-axis) for each of the rivers in the Apalachicola–Chattahoochee–Flint (ACF)River Basin. Colors correspond to the rivers in the basin; that is, blue circles represent Apalachicola River withdrawals, red circles representChattahoochee River withdrawals, and green circles represent Flint River withdrawals. Circle sizes correspond to the percent demand each sectorwithdrawals within its corresponding river compared to the total demand of all sectors within the corresponding river. Public supply andthermoelectric withdrawals are the dominating sectors in the Chattahoochee River. The Apalachicola primarily supports thermoelectric power and theFlint River Basin primarily supports the agricultural economy in Georgia.

Underpinning all aspects of development, water linkstogether food and energy and is central to greengrowth, sustainable economies, and reliable resourcesupply. As noted by UNECSO,49 ‘it is the only mediumthat links sectors and through which major globalcrises can be jointly addressed’. We use three casestudies to explore water security, food security, andenergy security three-way interactions and show howwater drives the interrelationship among the threeresources.

Apalachicola–Chattahoochee–Flint (ACF)River BasinThe ACF River Basin is located in the southeasternUnited States. The Chattahoochee River begins innortheastern Georgia and is impounded by damsoperated by the US Army Corps of Engineers. Oneof the important upstream reservoirs, Lake SidneyLanier, provides flood control and recreation, as wellas residential and commercial water for Atlanta’smetropolitan area. The upstream demands often limitdownstream flow and, concomitantly, thermoelectricpowerb and hydropower generation (Figure 2). TheFlint River Basin primarily supports the agriculturaleconomy in Georgia. The Chattahoochee and Flintrivers meet and flow into Florida’s Apalachicola Riverand Bay, where the preservation of reliable flowis critical for navigational purposes and ecologicalservices. The Apalachicola Bay is home to one ofthe world’s most biodiverse conservation sites andsupports a multibillion-dollar fishing industry.52

The ACF River Basin experienced positivepopulation growth from 2000 to 2010. The Atlanta-Sandy Springs-Marietta metropolitan area populationincreased by more than 90,000 from 2010 to2011—the seventh largest increase in population inthe United States.53 As a result of this urban growth,the portfolio of freshwater withdrawal has changedover the past three decades. In 2005, public supplywithdrawals from the ACF River Basin accountedfor more than 30% of total withdrawals; in 1970,public supply withdrawals were less than 10%, whichis comparable to the national proportion of publicsupply freshwater withdrawals over the past 35 years(Figure 3). Although public supply withdrawals arereturned to the system and available for other uses,discharge is treated (requiring energy) before it isreleased back into surface water systems. Wastewaterdischarge increased by more than 80% between 1990and 2005, primarily as a result of urban growth withinthe ACF and extensions of service outside the basin.51

In addition to significant urbanization in thepast three decades, the river basin has experiencednumerous multiyear droughts,54 and drought-relatedstresses are projected to become more severe overthe next century. The National Climate Assessmentand Development Advisory Committee55 identifiedthe southeast as a region ‘exceptionally vulnerable’to climate variability and change. Drought eventsintensify water scarcity, and this stress increases thestrength of the links among water resources andfood and energy resources, transforming traditionally



Public Domestic Commercial-industrial-mining

Agricultural-aquaculture-livestock Thermoelectric

US US1970 2005(a) (b)

ACF ACF

FIGURE 3 | Changing freshwater withdrawal (surface water andgroundwater) demand patterns from (a) 1970 to (b) 2005. The outercircles show freshwater withdrawal21 percentages by sector for theUnited States. The inner circles show freshwater withdrawal51

percentages by sector for the Apalachicola–Chattahoochee–Flint (ACF)River Basin. In 2005, total withdrawals in the United States increased byapproximately 10% 1970 values, and total withdrawals in the ACF RiverBasin increased by approximately 35% 1970 values.

two-way interactions into three-way interactions. Inyears when rainfall is plentiful, there is likely tobe enough water to satisfy demands placed by theurban population, the food and energy sectors, andecosystem services. In drought years, however, choicesmust be made. Downstream users need adequate waterin-stream, but upstream users withdraw and consumewater for their needs. When this spatial dimension ofwater is juxtaposed with the temporal component ofsupply and demand, management of water resourcesgets complicated. The agricultural sector is most likelyto irrigate crops during the summer months, the sametime that Apalachicola Bay oysters are in need offresh water56 and thermoelectric and hydroelectricplants are running at full production to satisfy thedemand for air conditioning. Droughts in the ACFcause competition for water, but only a regional stresson water resources that also affects only regionalfood and energy production; there are no substantialimplications for communities outside the basin. Infact, as a result of the global market that operatesfor a developed country, regional food security is notaffected very much by drought in the ACF.

Conventional management of the ACF RiverBasin has focused on infrastructure solutions toincrease supply of water resources. This approachoften fails to gain widespread acceptance. Stake-holders most worried about the environment arenot often involved in decision-making meetings56

and involving them in the future may be politicallyinfeasible if there is a preexisting political conflict.

This not only causes distrust among competitive waterusers but also overlooks the strong link betweenecosystem services and economic vitality.57–59

Feldman56 suggests taking actions that are reversibleand experimental in nature so that the partiesinvolved can learn from mistakes and incrementallyimprove policy. Because tensions have escalatedin the ACF during drought conditions, anotherchallenge is to define specific plans to account fortime-variable conditions, but at present, few wateragreements include clauses for temporal changes inflow, intensifying conflicts during drought events.60

One part of a path to determining the extent of stresson water during drought in the future will be choicesabout how electricity is supplied to the ACF.61,62

Overall, an integrated water-energy managementapproach that involves a range of stakeholders isrecognized as necessary to resolve water disputes inthe ACF.54,63

Sri LankaThe current picture of Sri Lanka—a nation thatis heavily reliant on agriculture to self-sufficientlymaintain food security but which is rapidly developingand expanding its urban infrastructure—is notuncommon within the region or among developingnations throughout the world. Sri Lanka is a tropicalisland nation of some 66,000 km2 with plentiful wateravailability on average; the mean annual rainfall ofalmost 2000 mm is unevenly spatially distributed, witha large ‘dry zone’ covering much of the arable landof the country. Sri Lanka’s population has increasedmodestly and is expected to continue to increase atabout a 1% growth rate per year for the next fewdecades.64,65

Agricultural production is a heavily prioritizedsector in Sri Lanka, with national self-sufficiencyin rice production a food security goal and witha strong cultural connection to paddy farming.Agriculture accounts for only about 15% of totalGDP, yet it covers about 40% of total land areaand incorporates more than 25% of the laborforce.66 Rice production has increased dramaticallyover the past several decades, in large part owingto a government resettlement program that opensland to paddy farmers in the dry zone throughprovision of irrigation water. This resettlement effortcontinues under a plan to develop urban centers inthe Southern, Eastern, North Central, and Northernprovinces that will expand access to electricity andpiped water to a population that is projected toreach 25 million by 2030.67 Historically, morethan 90% of Sri Lanka’s electricity was producedthrough hydropower, but this percentage dropped



FIGURE 4 | Electricity generation in Sri Lanka. Hydropower supplied over 90% of the total in the early 1990s but supplies only about 40%currently.64,69

to about 45% in 2010.64 Total hydropower outputhas increased only gradually since 1990, becausenew sites for development are now limited.68 In1990, hydroelectric power plants supplied about 3100gigawatt hours (GWh) to the national grid and therewas a tiny amount of electricity generated by oil-fueledthermal power plants; in 2007, hydropower supplied3950 GWh and thermal plants supplied 5900 GWh.68

The increased reliance on thermal power generationnotwithstanding, hydropower still represents a veryimportant source of electricity (Figure 4).

The process of making decisions about alloca-tion of water between irrigation and hydropowerc,70

in Sri Lanka is complex; allocation of water takesinto account seasonal precipitation projections andincludes a wide range of stakeholders. Traditionally,irrigation–hydroelectricity trade-offs are a matter oftiming; that is, the conflict is more about setting thedischarge schedule so that it either meets peak elec-tricity demand or peak agricultural demand. In SriLanka, however, the decision has a strong spatiotem-poral component because both systems are gravitydependent. The reservoirs and their releases are set ata high elevation. The potential energy of water canbe either used to divert water into a canal for water-intensive flood irrigation that produces twice as muchoutput in the north than in the east or to maintainthe natural flow of water, producing twice as muchhydroelectricity in the east than in the north. There-fore, even in years when rainfall is plentiful, thereis an uncertainty component that results from thespatial and temporal distribution of water. The cor-relation between rainfall and both paddy productionand hydropower generation for the country suggeststhat trade-offs are currently being made (Figure 5).

Current drought events have highlighted SriLanka’s water vulnerabilities and the trade-offspresent in managing its water resources. Countriessuffering from water scarcity often import water-intensive goods so that they can focus their limitedresources on those that will result in a net benefit or acomparative advantage in production. This concept ofwater embedded in products, including its applicationto food and crops, is referred to as virtual water.71–73

Sri Lanka endured back-to-back drier than normalmonsoon seasons in the late 1990s. As a result, thecountry rose to the top of the global virtual waterimporters during those years,74 allowing them tosecure their people with food. Research looking at therole of virtual water to achieve food security and othernational goals suggests that focusing on virtual wateralone will not be sufficient in determining optimalpolicies.75,76 In the short term, it is recognized thatthe globalization of virtual water prevents conflictsand increases food security.74,77

In the future, government policies supportingdomestic rice production and a strong historic andcultural attachment to paddy irrigation suggest thatthe agricultural sector is likely to be preferred.Nevertheless, the government’s current emphasis oneconomic growth hints that priorities may change.Addressing problems of agricultural water shortageis already a consideration in Sri Lanka as farmershave adapted to drought. A variety of measures haveproved to be at least partially successful, includingusing drought tolerant crops, adopting new irrigationtechnologies, and engaging in collective activitiesto minimize extreme impacts to individuals.78,79

Additional actions will be required in the future,however.



FIGURE 5 | Trade-off frontiers between hydropower and irrigation. The annual rainfall at Kothmale Dam,64 a large reservoir at the headwaters ofthe Mahaweli system, is used as a proxy for water availability in the system; annual rainfall is plotted as red circles and labeled. The blue curves arestylized trade-off frontiers for annual rainfall of 100, 150, 200, 250, and 300 cm. For high rainfall (e.g., 300 cm), the hypothesis is that there is enoughwater that high levels of both paddy production and hydropower are possible—there is little trade-off. For low rainfall (e.g., 150 cm) the hypothesis isthat trade-offs are significant; for example, a change in hydropower from about 2200 to 3100 GWh results in a drop in paddy production from5 × 106 to 1.5 × 106 metric tons (paddy production and hydropower generation data are at the national level). The data is not perfect (e.g., theactual annual rainfall outlier represented by 213 cm), but a general trade-off trend is noticeable.

Urbanization and economic growth are rootedin increased energy production, also increasing waterdemands. Significantly more water might be usedto generate hydropower if farmers were convincedto change their behavior with regard to irrigation,but achievement of this goal may be socially,politically, culturally, or economically infeasible.80 AsManthrithilake and Liyanagama81 state, ‘The waterallocation process within this ‘‘water–food–energynexus’’ with its complex interconnections is a difficulttask and has a significant impact on the social andeconomic life of the country’. The use of the authors’simulation model in a participatory process suggeststhat informed decision making may play an importantrole in achieving food and energy security for SriLanka.81

BrazilDespite some pessimism about the overall feasibilityof having biofuels play a large role in a sustainableglobal water–food–energy framework, is it possible tohave regional exceptions? Brazil is a country that hasmade very significant investments in the developmentof a biofuel industry that began several decades ago.82

In 1975, Brazil established a program, Proalcool, toconvert sugar to ethanol. The move came 2 yearsafter the 1973 oil crisis, but the program was reallyaimed more at shoring up the sugar cane industry

than producing renewable energy. In 1979, followingthe Iran–Iraq war, however, the Brazilian governmentexplicitly moved ahead with ambitious biofuel plans asthe main goal of meeting energy security needs. Brazilis now a major exporter of ethanol. According tothe US Energy Information Administration,83 Brazilproduced about 23% of the total biofuels globallyin 2011, and it supplied about 20% of internalproduction of liquid fuels (Figure 6).

Brazil is a country with abundant water andland resources.d A direct effect of biofuel productionon water resources within the country is not expected,but there are concerns, as with all intensive cropgrowth, that water quality could be adversely affectedowing to application of fertilizers and pesticides.85

The expansion in land clearing, its potential impacton biodiversity,86 and the potential of biofuels to takeover cropland are of concern. Land-use change forsugar cane production to produce ethanol, to date,has been mainly through displacement of pastureland and has not been at the cost of deforestation.87

Nevertheless, a concern remains for the future. Theproximity of the cane-growing areas to the remnantsof the Atlantic Forest poses a potential threat tothat fragile ecosystem.86 Indirect land-use changescould threaten the Amazon rainforest, for example,by expansion of soy farms.88 The current ban onexpansion of soy farming into the Amazon foresthas been successful, and it is important to maintain



FIGURE 6 | Biofuel (biodiesel plus bioethanol) production in Brazil. Biodiesel feedstock is primarily soybeans (77%) with animal tallow second(16%).83

it.85,89 Currently, water and land resources in Brazilappear adequate for expansion of both biofuel andfood production,90 so a three-way competition amongwater, food, and energy within the country itself isunlikely to manifest in the next few decades. Concernthat food prices affected by ethanol production inBrazil may impact food security in other countries hasalso not been evident to date.91 This is not to saythat there are no problems and that finding solutionsto them is not critically important. The recommendedactions to promote sustainability include adoptingmeasures to control erosion, controlling nitrogenrunoff, protecting riparian ecosystems, and promotingproductivity growth on existing agricultural land toavoid expansion into natural ecosystems.85,92

Water as the Driving ForceThe distribution of water, food, and energy resourcesis uneven; supplies and demands vary in bothspace and time. Water and energy reserves donot respect political boundaries,93 but water hasadditional dimensions of complexity—it is a finite,mobile resource.94 Water available as groundwatercan be consumed faster than reserves are maintainedand is often nonrenewable on human time scales.Water available as surface water has upstream anddownstream users, is prone to variability in flow, andusually is considered renewable.

Because of the temporal and spatial dimensionsof water supply (i.e., weather is chaotic), waterdisputes can occur even in areas where water isplentiful on average. The ACF is an illustrativeexample of how multiple, competing demand-sidesectors, combined with population and urban growth,

extreme drought events, and lack of collectiveaction, can cause tensions over water resources ina traditionally water abundant area.

Upstream and downstream users often haveconflicting needs; some users consume, withdraw, ordivert water, whereas others use the water in situ. SriLanka’s choices involving food and energy securityare a descriptive example of trade-offs resulting fromstressors and limiters.

The Brazil case study examining biofuelproduction highlights the importance of water indriving three-way interactions. In the absence ofwater stress, there is less competition for waterand fewer trade-offs to be made; consequently,water–food–energy interrelationships are limited totwo-way interactions.

As mentioned above, we believe that wateroccupies a special niche in our discussion. Food andenergy are private goods and sold in the global marketas commodities. Water, on the other hand, is botha public and private good; there are human needsfor water (e.g., drinking and bathing),95 but there arealso human demands for water as a commodity (e.g.,landscaping and car washing).94 Nevertheless, wateris undervalued96 and rarely priced as a commodity.Although water does not have substitutes, at least notin the traditional sense, food and energy resourcesare often transported over large distances, and bothresources have substitutes. It is not economicallyfeasible to move water over large distances becauseof its weight,94 so communities with water deficits orwith a comparative disadvantage in water resourcesstrategically import virtual water—that is, waterembedded in commodities.71,73,75



Virtual water embedded in various products(e.g., grain) is often underpriced, so the importingeconomies get a subsidized bargain, while meetingtheir water needs without confronting the underlyingissue of water scarcity.71 Although virtual water tradecan help achieve food security for communities thatare faced with immediate food and energy trade-offs(e.g., Sri Lanka in the late 1990s), there are potentialdrawbacks of global reliance on strong networks.D’Odorico et al.97 suggest that long-term relianceon the global trade of virtual water reduces societalresilience; in times of extreme water scarcity, there arefewer options available. Thus, ‘land grabbing’, or theacquisition of arable land in developing countries, is arecent trend among water-deficient regions hoping togain some control of virtual water. Land grabbing notonly allows governments to increase food security butalso provides opportunities for biofuel production.98

Therefore, it is no surprise that the ‘land grabbing’phenomenon is associated with the acquisition offreshwater resources associated with the purchasedland, as much as it is associated with the acquisitionof the land itself.99

The water requirements for biofuels often putbiofuels at odds with food and energy security, but thisis not the case for Brazil. It is not surprising, therefore,that almost 5% of the total global grabbed land isin Brazil, accounting for approximately 20 billion m3

of grabbed green water.99 If water stress did strikeBrazil, it may be likely that countries dependent onBrazil’s virtual water exports (i.e., crops and biofuels)will be affected, but the in-country impact likely willbe small.

Water holds great cultural and spiritualsignificance, and, therefore, political trade-offs andtrans-boundary trade-offs are laden with morethan simple economic concerns. Water is asymbolic resource,94,100 adding an additional layerof complexity, as illustrated by our Sri Lanka casestudy—agriculture is an important dimension not onlyin food security but also in rural livelihood. Withgrowth and projected climate change, Sri Lanka willbe faced with making trade-offs: water for energyand economic growth or water for agriculture, foodsecurity, and cultural preservation.101 This trade-offbetween water for food and water for energy is notunique to Sri Lanka or countries in south Asia. ‘Thereis a broad agreement . . . that there will be significantlyincreasing water scarcity that will turn ‘‘water’’ intoa key, or the key, limiting factor in food productionand livelihoods generation for poor people in . . . ruralAsia and most of Africa, with particularly severe waterscarcity in the bread baskets of northwest India andnorthern China’.3

A LOOK TO THE FUTURE

Under current global pressures, solutions to overcomescarcity in a way that meets all demands aresought. We have argued that water resources drivewater–food–energy three-way interactions, but werecognize that solutions need to be all encompassing:

A number of international organizations highlightthe water–food–energy nexus as illustrating the mostdifficult choices, risks and uncertainties facing policy-makers today. Examples abound of the variousintended or unintended consequences of favouringone pillar over the other (e.g. food security versusenergy security). A key challenge is to incorporatethe complex interconnections of risks into responsestrategies that are integrated and take into accountthe many relevant stakeholders.48

Doom and Gloom?The issues that we have reviewed in this article canseem to present overwhelming obstacles to reachinggoals for water, food, and energy security for aglobal population expected to reach 9 billion by themiddle of this century. Concerns that the humanpopulation may face threat of collapse in the absenceof efforts to conserve resources have been expressedfor a long time and have been addressed evenrecently in the scientific literature.102–106 The view isessentially Malthusian—populations tend to consumeresources and catastrophically collapse at some point.Analyses of historical (local) population collapse andmathematical modeling of populations do not offermuch comfort that a catastrophe can be avoided.107

There is room for optimism—that human populationswill be stabilized,102 that technology will assist inthe move toward global sustainability,103 and that‘green economies’ will emerge.108 Nevertheless, eventhe optimistic view that economic and technologicaladvances will come to the rescue and avert a globalcrisis is suspect when considered carefully.105,109,110

Essentially, all serious analysts indicate thatfinding solutions to our local to global water,food, and energy security problems will requiresignificant action, either through institutional andbehavioral paths (i.e., nontechnological actions) ortechnological and infrastructural paths (Table 2).Of course, it is overly simplistic to think thattechnological and nontechnological solutions forwater, food, and energy security can be pursuedindependently. For example, it is essentially certainthat the amount of food produced in the world willhave to increase substantially to meet the needs of theglobal population in 2050. The trick is to increaseaccessibility and increase the amount produced while



decreasing the energy consumption and impact on theenvironment and on water resources in particular; thatis, a mixture of technological and nontechnologicalwater–food–energy interrelated approaches will beneeded.111

Opportunities for Water, Food, and EnergySecurityTo understand better the opportunities, it is importantto understand first the context of resource scarcity.Problems of water, food, and energy scarcity canbe framed in two ways—economic scarcity andphysical scarcity. Economic scarcity occurs whenthere is a lack of investment in resources and theresources’ infrastructure; communities with sufficientresources but limited infrastructure to access theresources face economic scarcity. Physical scarcity,on the other hand, relates to the absolute measureof the amount of the resource; it occurs whensupply does not meet human and environmentaldemands, even after accounting for future adaptivecapacity.3,29 Using these definitions, we note a dividebetween developed and developing worlds; developedcountries often have sufficient infrastructuree andcapital to investment in infrastructure to relievetheir resource scarcity problems, whereas developingcountries do not.

For example, malnutrition exists in CentralAfrica, a region with abundant water resourcesrelative to water use; the lack of human, institutional,and financial capital limit access to the water and, thus,create an economic scarcity of water that translatesto food insecurity.29 This economic scarcity of wateris reflected in recent land and water grabs. Africaaccounts for 47% of the global grabbed area, andmany countries within the continent exhibit highgrabbed to cultivated area ratios, suggesting thatthe area was not previously cultivated.99 Land andwater grabbing provides economic opportunities forrural farmers and can support technology transfers,98

but inadequately managed foreign investments inagricultural land can lead to political instabilityand unsustainable practices.98 The core argument infavor of land grabbing is that foreign investmentscan overcome economic scarcity and benefit thedeveloping country and the resulting exports of virtualwater can benefit the developed country.

In addition to placing water, food, and energyin the context of physical and economic scarcity,opportunities to meet water, food, and energy securitycan be framed according to two paths forward—asoft path and a hard path. An essential part of a pathtoward sustainability in the future is improvement

in the efficiency with which water, food, and energygoods and services are produced and used. In anideal case, we could match the needs of userswithout seeking sources of new supply.113 This isthe foundation behind the concept of the soft pathin water,113,114 an ideal that originates from theenergy sector,115,116 and can also be applied to food;there is a finite amount of local resources and asoft-path approach focuses on reducing demand byproviding water, food, and energy services moreefficiently with a smaller physical quantity. Water,food, and energy policies that focus on the soft pathconcentrate less on increasing supply through largeengineering feats and more on maintaining serviceat a modified consumption rate.117 Thus, the softpath to water, food, and energy security is lessabout the quantity of the resource and more aboutthe productivity and efficiency of the resource orensuring that all demand-side sectors can effectivelyprovide services and goods in a way that maintains orimproves the lifestyle of society. Gleick113,114 andLovins115,116 combine elements of technology andbehavior, ultimately defining their soft path as flexible,polymorphous solutions focused on the quality ofservices and their hard path as inflexible, monolithic,solutions focused on the quantity of resources.

Both the context of scarcity and the pathsforward complicate the analysis of opportunities.Although it may appear that a hard path, such asnuclear-powered desalination, would address physicalscarcity by manufacturing large quantities of freshwater, this solution is limited by economic scarcity(i.e., the investment in desalinization infrastructureand maintenance). An intuitive soft-path solution,such as conservation, appears to address economicscarcity by reducing demand so the equilibriumpoint moves farther down the supply curve, butwater is not a private good and typically is notadequately priced.118 Conservation will play a vitalpart in maintaining resource security in developedcountries, where economic scarcity is not a dominantproblem and people are more disconnected from theirresources.

Opportunities for Overall SecurityAlthough there are opportunities specific to eachof the resources, there are also opportunities withtechnological and nontechnological options thatwould reduce the stressors and limiters on all threeresources (Table 2, A): reproductive education andservices, increased equity and equality, and climatechange actions. Paths forward must address bothaspects of scarcity and take into account trade-offsand constraints.119



TABLE 2 Technological and Nontechnological Opportunities to Meet or Maintain Water, Food, and Energy Resource Security

Resource Nontechnological Technological

(A) All resources Enhance reproductive education Improve access to birth control and reproductive healthservices

Improve equality through institutional transparency andpromoting representation

Improve access (supply) and control (storage) ofresources through financial (e.g., microfinance) andinfrastructural (e.g., desalinization plants, carboncapture, and storage) investments

(B) Water Encourage behavioral changes to conserve energy andfood

Use energy-efficient or water-efficient energytechnologies (e.g., dry and hybrid cooling, reclaimedwater); build reliable transportation and energyinfrastructure (e.g., roads)

Encourage behavioral changes to consume less water Encourage efficient and diverse water-use technologies(e.g., rainwater harvesting and storage)

Implement strict building standards for water use

(C) Food Encourage best management practices in irrigation(e.g., no till, reduce excessive fertilizer use)

Use efficient irrigation technologies (e.g., drip irrigation,reclaimed water, capture nutrients, and recycle)

Encourage behavior changes for sustainable diet (e.g.,vegetable-based diets and lower calorie consumption)

Use genetically enhanced plants and animals

Implement consumer awareness campaigns to reducefood waste

Build reliable transportation and energy infrastructure(e.g., roads and refrigeration systems)

(D) Energy Encourage behavioral changes to conserve water andfood

Use energy-efficient or water-efficient watertechnologies (e.g., rainwater harvesting and storage,dual flush toilets); build reliable transportation andenergy infrastructure (e.g., roads and refrigerationsystems)

Encourage behavioral changes to consume less energy Use efficient and diverse energy portfolios with cleanand renewable energy sourcesImplement strict building standards for energy

There are opportunities that reduce the stressors and limiters on all three resources (A), in addition to opportunities that reduce the stressors and limiters on,specifically, (B) water, (C) food, and (D) energy. Many opportunities cut across the nontechnical and technical spectrum, as well as the water, food, and energycategories.

Demand for resources is driven in part bythe size of the population. The question posed byEhrlich and Ehrlich,104 ‘Can a collapse of globalcivilization be avoided?’, is rhetorical, but emphasizesthat the growth of the human population cannotgo unabated if demands for resources are to becontrolled. Despite the fact that a reliable estimateof the Earth’s carrying capacity for humans cannotbe calculated,120 it is clear that the populationgrowth rate must continue to decline to stabilizetotal population. The issue is particularly seriousin the poorest countries where water, food, andenergy security concerns are greatest. Support forvoluntary family planning programs is seen as the mostpromising policy approach,121,122 an approach thatincludes reproductive education, as well as reducinggender inequality through institutional transparencyand promoting representation. Access to birth controlmethods and access to reproductive health servicesare limited by economic capacity, so economicinvestments will be necessary.

Regardless of efforts undertaken now, effectswill not be immediate. In the meantime, institutionaland behavioral changes, such as reducing social-classand gender inequality and supporting adaptationto climate change, can be encouraged. On thetechnological side, efforts can be made to improveaccess and control of water, food, and energythrough financial and infrastructural investments andto promote mitigation of climate change. Realistically,many of these opportunities are crosscutting and willinvolve both nontechnical and technical elements.

Opportunities for Meeting Water SecurityWe have argued in this article that water plays apreeminent role in the water–food–energy nexus. Itfollows that water will also be a very importantingredient in solutions to problems. Projectionsof resource needs over the next several decadesare a source of very significant concern forwater managers.45 The emerging globalization ofwater resources, however, argues that international



cooperation and collaboration will be necessaryin the future.48 Analyses of previous efforts atinternational water management, orchestrated bydeveloped countries, are not very encouraging,123 sothere is much work to be done.

Solutions on the technology and infrastructureside focus on improving financial and infrastructuralinvestments,124 as well as installing energy- or water-efficient technologies10,125 (Table 2, B). In California,for instance, regulated energy utilities spent 3 billiondollars in 2010–2012 promoting energy efficiency; aspart of this campaign, utilities focused on reducinghot-water use and encouraging water conservationthrough home appliances. The energy utilities wereinterested in the full lifecycle of water ‘because thisinformation could allow them to claim credit forsaving energy by saving water in addition to the energyrequired for direct heating that they already claim’.126

On the nontechnological side, there are opportunitiesto encourage behavioral changes to conserve water,as well as food and energy.

Opportunities for Meeting Food SecurityGarnett127 identifies three conceptualizations of thefood security problem: a socioeconomic component,involving global institutions and the economy;a production component; and a consumptioncomponent, which involves diets and population.We add a fourth viewpoint to these—food wastage(Table 2, C).

Technological solutions to increasing foodproduction have been dominant to date. Cropproduction grew by 28% between 1985 and 2005,with 25% attributed to yield increases.111 Theyield increases occurred by virtue of a doublingof irrigated area and a 500% increase in fertilizerapplication.111 Part of the increase in food productionmay be attributable to genetically modified plants andanimals, allowing plants to overcome environmentalpressures and animals to develop more quickly,but this has not been demonstrated clearly.128,129

Nevertheless, within the next century, more radicalgenetic manipulations and enhancements may befeasible,130 and future technological advances willbe necessary to address global food security issues.Spiertz131 notes that agronomists need to continueto improve crop properties to improve efficiency ofwater and nutrient use, including developing varietiesto adapt to climate change.

Overall, food production has helped increasefood security, but it is just one piece of the puzzle.Opportunities for agricultural intensification to closethe yield gap (the difference between what is produced,especially in underdeveloped countries, and what

could be produced with best practices) must bepursued.132 Farmers could switch from traditionalcrop rotations and traditional crop varieties that arelikely to suffer from climate change—corn, soybeans,and cotton—to new patterns and crops better suitedfor the changing climate conditions.55

Much of the focus on future forecasts of fooddemand has been to extrapolate the increasing demandfor meat protein, a trend that is acknowledgedto exacerbate the stress on water and energyresources. For example, the water footprint forvegetables is about 300 L/kg and for beef is about15,000 L/kg.133 Although growth in animal proteinin the diets of people in the developing world isalmost certain to occur, there is growing recognitionthat the dietary preferences of people need to beshifted.106 Changes in eating habits will be anessential ingredient in achieving food security in thefuture. Behavioral changes, despite the problematicnature of determining how to develop them, willbe necessary.134 At a basic level, analysis indicatesthat absolute food availability, in terms of caloriesand protein available to humans, can be enhancedby shifting cereal production away from feedstockand energy crops.111 It is also clear that humanhealth outcomes can be improved if diets are shiftedaway from meat and toward more grains, fruits, andvegetables.106,127

Recognizing that roughly one third of theworld’s food produced is wasted indicates that thereare steps that can be taken to conserve these resources.Food is wasted along the entire supply chain, fromagricultural production through consumption. Indeveloped countries, much food is wasted by con-sumers, presumably because they can afford to do so.Raising public awareness through education is a neces-sary step to reduce such waste.135 In developing coun-tries, fresh produce is often lost preretail because ofpoor food-chain infrastructure, including processingand distribution, or the lack of investment in cold stor-age. Public investment in transportation infrastruc-ture, combined with increased capital for things suchas refrigeration are important for reducing waste andsecuring food resources.130 Development of farmerorganizations to promote resilience and avoid prema-ture harvesting and development of market coopera-tives to promote efficient distribution of food are otherways to minimize waste in developing countries.135

Part of the solution also involves eliminating wasteat the retail and postretail stages (i.e., discardingfood because of cosmetic reasons).106,127,130 Changingthe perspective of people and improving internationalinstitutions is far from an easy task, but arguably onethat must be engaged. Ehrlich and Ehrlich104 suggest



that, to avoid a collapse of global civilization ‘inter-national negotiations will be needed, existing interna-tional agencies that deal with them will need strength-ening, and new institutions will need to be formed’.

Opportunities for Meeting Energy SecurityDespite continued warning signs that climate changeimpacts may become severe over the next severaldecades, we have yet to see much in the way of areal commitment to a more environmentally benignenergy path. Again the issues are complex, and it isapparent that economic, social, and political levers areneeded to move the world in the right direction, andthat a substantial change in how nation states viewsecurity may also be a prerequisite.136 Consideringthe following statistics, it is patently obvious thatadvances will be needed along both technological andnontechnological sides (Table 2, D) in the energysecurity sphere to avoid water and food conflicts.

• Between 2000 and 2010, total world generationof electricity went from about 14,600,000 GWhto about 20,200,000 GWh, an average annualgrowth rate of about 3.3%.137

• Between 2000 and 2010, world generation ofelectricity from hydropower went from about2,600,000 GWh to about 3,400,000 GWh, anaverage annual growth rate of about 2.9%.137

• The growth in demand for electricity to 2035 isforecast to increase at a rate of about 1–2% peryear.138

• Between 2000 and 2011, world production ofbiofuels rose from a little over 300,000 barrelsper day to almost 1,900,000 barrels per day, anaverage annual growth rate of almost 18%.138

The technological advances to manage water inthe context of thermoelectric power generation havecomplex interactions among cost, energy efficiency,and water savings.139 Once-through cooling systemswithdraw large amounts of water but return most ofit to rivers or lakes, albeit at a higher temperature,whereas closed-loop cooling systems withdraw lesswater but consume more of it.140 Dry coolingsystems reduce water withdrawal and consumptionsignificantly, but there is an energy penalty—that is,less electricity is generated per unit of fuel consumedwith dry cooling than with wet cooling.139 Theoption of construction of large hydroelectric damshas well-documented environmental downsides, butthe potential for generating electricity is large andthe benefits, especially in developing countries, canbe large as well. Technological advances that have

been put forward are the development of small-scalehydroelectric installations, which are distributedand may have significant advantages in countriesthat do not have a modern electrical grid. Thesesmall-scale installations have been touted as avoidingthe majority of the adverse environmental impactsassociated with large dams, but analyses indicate thatthis may not be the case.141

The technology-related advances for biofuelsrevolve around further development of second-generation methods, that is, those that do not usefood crops as feedstock. Provided that productionof biofuels from cellulosic materials can be madeeconomically feasible, the use of marginal lands inthe United States (and elsewhere) may prove to bebeneficial.142 Nevertheless, the challenge of managingland for energy production, as well as food productionand biodiversity conservation, is huge. Policies willhave to resolve trade-offs involving food, renewableenergy, biodiversity conservation, and environmentalpressures from intensive agriculture.143 There havebeen many research efforts directed at use of cellulosicmaterial as feedstock144 and at using algae to producebiofuels.145 Not everyone agrees that developmentof biofuels represents a high priority goal, butregardless of viewpoint, it is clear that the social andenvironmental impacts of biofuel production mustbe evaluated.146 There is considerable debate aboutwhether first-generation biofuels improve energysecurity,32 and certainly, there is much that remainsunknown about how and if second-generation fuelswill in fact prove to be a panacea.

CONCLUSION

Where Do We Go from Here?In the abstract, resolving the conflicts surroundingresource scarcity can be viewed as an optimizationproblem of allocating scarce resources to maximizeutility. For instance, scholars tend to agree that wateris a common-pool resource, but there are manytheories about the management of common-poolresources. Some scholars recommend a coerciveforce from outside the users’ domain, governmentownership, or marketable permits. Others suggestself-organization or a more collaborative approachamong resource stakeholders.2,147 All resource prob-lems present different challenges, and stakeholderpreferences and perceptions vary across the problemsets. Thus, there is no single solution for ourlocal or global resource problems. Each problem isunique and requires special attention to its specificsocial-ecological system.147



The challenge to make a transition to sustain-ability in the world is daunting, especially when itis clear that coordinated international cooperation isrequired. But there are clear, concrete steps that canbe taken to mitigate the water–food–energy collision,a few of which we presented above (Table 2).These and other measures15,118,148,149 can form acomprehensive approach that incorporates soft andhard paths to managing the risks that face humanitywith respect to physical and economic water, food,and energy security. Impacts may be regional andglobal, but solutions need to be localized and take intoaccount cultural norms, economic development, andgeographic environmental features. Different man-agement options need to be evaluated systematicallyto understand the costs and benefits150 associatedwith the people, the planet, and global prosperity.Achieving water, food, and energy security willrequire many different techniques at various scales,incorporating the full range of stakeholders involved.

NOTESa In January 2013, a federal appeals court vacated theUS EPA stipulation regarding cellulosic biofuels.b The distinction between water that is consumedand water that is withdrawn is not trivial,

especially with regard to thermoelectric plants.Recirculating systems consume twice as much wateras once-through facilities, but once-through facilitieswithdraw significant amounts of water that are laterreturned at an increased water temperature, oftencausing thermal pollution.8,50

c Although hydropower often is considered to benonconsumptive in terms of water, an analysis of largehydroelectric dams worldwide indicates that the bluewater consumption from hydropower dams amountsto about 10% of the blue water consumed by crops.70

d This case study does not include dams, hydroelec-tricity, or the Amazon River specifically. Three-wayinteractions among water, food, and hydroelectricitydo occur in Brazil, but because we cover similar three-way interactions in the two previous case studies, weuse Brazil to explore the water–food–biofuel nexus.84

e For the most part, it is true that developedcountries are not plagued by economic resourcescarcity. By definition, developed countries have morestable economies and governments than developingcountries, as well as more advanced technologies andinfrastructure. Nevertheless, even developed nationslike the United States are subject to continualrequirements to invest in infrastructure.112

ACKNOWLEDGMENTS

The work was partially supported by an EPA STAR Fellowship (DP) (EPA FP917358) and by a grant fromthe National Science Foundation (GMH) (NSF-EAR 1204685). We thank Amanda Carrico, Leslie Duncan,Jonathan Gilligan, and David Hess for commenting on a draft of this manuscript.

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