OPINION

Putting all foods on the same table: Achievingsustainable food systems requires full accountingBenjamin S. Halperna,b,1, Richard S. Cottrellc,d, Julia L. Blanchardc,d, Lex Bouwmane,f,g, Halley E. Froehlicha,h,i,Jessica A. Gephartj,k, Nis Sand Jacobsenl, Caitlin D. Kuempela, Peter B. McIntyrem, Marc Metiann,Daniel D. Morano, Kirsty L. Nashc,d, Johannes Többeno, and David R. Williamsb,p

Improving global food systems is essential to addressingclimate change, mitigating biodiversity loss, and meet-ing both sustainability and human development goals.International assessments from the IntergovernmentalPanel onClimateChange and Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Ser-vices and business and technology innovations suchas lab-grown and plant-based meat, as well as manyconsumer diet trends, can all be traced to studies thatidentify undesirable impacts of certain food systems.

Yet the evidence underpinning many widely toutedrecommendations about what to grow and eat isremarkably sparse and generally biased.

We know that not all food is created equal in termsof environmental impact (1–3). However, most pastresearch has focused on only a few key foods (e.g.,beef and staple crops) and only a few environmentalstressors (particularly greenhouse gas emissions). Inaddition, these studies tend to be confined to a fewcountries, and many nations suffer from poor knowledge

The web of food impacts and interactions is challenging tomap, let alone fully assess. Wemust address the holes in foodassessment studies and the paucity of linkages among foods in these assessments to fully understand the cumulativeimpact of food production. Image credit: Shutterstock/Olga Klochanko.

aNational Center for Ecological Analysis and Synthesis, University of California, Santa Barbara, CA 93101; bBren School of Environmental Science &Management, University of California, Santa Barbara, CA 93106; cCentre for Marine Socioecology, University of Tasmania, Hobart 7004, TAS,Australia; dInstitute for Marine and Antarctic Studies, University of Tasmania, Hobart 7004, TAS, Australia; eKey Laboratory of Marine ChemistryTheory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, People’s Republic of China; fDepartment of EarthSciences, Faculty of Geosciences, Utrecht University, 3508 TA Utrecht, The Netherlands; gPBL Netherlands Environmental Assessment Agency,2500 GH The Hague, The Netherlands; hEcology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106; iEnvironmentalStudies, University of California, Santa Barbara, CA 93106; jNational Socio-Environmental Synthesis Center, Annapolis, MD 21401; kDepartment ofEnvironmental Science, American University, Washington, DC 20016; lNational Research Council, Washington, DC, 20001; mDepartment of NaturalResources, Cornell University, Ithaca, NY 14853; nRadioecology Laboratory, International Atomic Energy Agency—Environment Laboratories (IAEA-EL), MC 98000, Principality of Monaco; oIndustrial Ecology Programme, Department of Energy and Process Technology, Norwegian University ofScience and Technology, Trondheim 7491, Norway; and pSustainability Research Institute, School of Earth and Environment, University of Leeds,Leeds, LS2 9JT, United KingdomAuthor contributions: B.S.H. secured the funding and prepared the initial draft; all authors helped conceive the work and edit the manuscript;and R.S.C., J.L.B., and B.S.H. developed the figures.The authors declare no conflict of interest.Published under the PNAS license.Any opinions, findings, conclusions, or recommendations expressed in this work are those of the authors and have not been endorsed by theNational Academy of Sciences.1To whom correspondence may be addressed. Email: halpern@nceas.ucsb.edu.This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1913308116/-/DCSupplemental.

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transfer between the scientific community and the pub-lic. Even the most wide-ranging assessments made todate (2, 4, 5) contain significant gaps (Fig. 1). Thesebiases arise, first, because substantial portions of theglobal food system are inaccurately or insufficientlyreported or effectively “hidden” from standard statistics(e.g., inland and small-scale fisheries, bushmeat, back-yard farming) and, second, because of an incompleteknowledge of the suite of environmental impacts andhow these propagate through the many linkages amongfood systems.

The web of food impacts and interactions are chal-lenging to map, let alone fully assess. Yet characterizingthese linkages is essential to understand the truecumulative impact of food production (2, 3). Withoutdoing so, society risks unknowingly exceeding regional,or even global, environmental boundaries or missingopportunities to steer food consumption and policy to-ward more sustainable foods and practices. Further-more, gaps in assessments are unevenly distributed.For example, in developing regions with rapidly grow-ing human populations, unassessed foods underpin thenutrition of millions and provide essential sources ofprotein for more than three billion people (3, 6, 7). Itis hard to imagine developing science-based foodpolicy for regions where so many of the common foodshave never been assessed in terms of environmentalimpacts.

Two major gaps in our understanding—substantialholes in food assessment studies and the nearly com-plete absence of linkages among foods in these as-sessments—limit our ability to link environmentalimpacts to food security. We show how this lack ofunderstanding undermines decision makers’ capacityto develop policies ensuring the planet can sustain-ably meet future human food demands. We recom-mend tackling these gaps by improving the envi-ronmental impact assessment of food productionand supporting the development of effective, integra-tive food policy.

Underassessed Foods and ImpactsOnly by putting all foods on the “same table” can wecomprehensively evaluate their relative environmentimpacts, and in turn, develop effective and efficientpolicies that ensure greater production with lowerenvironmental cost across all foods. “Underassess-ment” is an acute problem for two reasons. Hidden,missing, and under-reported (hereafter collectivelycalled underassessed ) foods represent substantialamounts of food production in many countries aroundthe world. Synthesizing data from open-access data-bases and published literature, we show that under-assessed foods represent more than half of animalproduction in 76 countries (see Ext. Data 2; Fig. S1)and more than 25% of total food in 40 countries (Fig.2). For those countries lacking data on their major foodgroups, it is impossible to generate informed plans forsustainability and food security. In addition, evenprominent well-studied foods commonly suffer fromvery narrow examinations—often only greenhousegas emissions implications and, perhaps, land and

Fig. 1. Comparative food impact studies published inthe last 10 years are skewed in favor of a handful oftopics. Coverage here was calculated as the number ofstudies that included each food type and associatedstressors and/or impacts. See Table S1 for details. Fulldata are available in Ext. Data S3. GHG, greenhousegases.

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freshwater uses are taken into account (Fig. 3). Theomission of marine stressors, such as acidifica-tion and plastic pollution, diminishes the value ofexisting marine food assessments and could exposemany regions of the world to tragic environmentalbreakdowns.

We hypothesize that the environmental impacts ofunderassessed foods are likely more diverse thanconventionally reported commercial agriculture andlivestock systems. This variation stems, in part, fromthe great diversity of species that are farmed andharvested within these underassessed sectors andfrom the greater range of production and capturemethods. Conventionally reported food consists ofrelatively few livestock species (cows, chickens, pigs,sheep, and goats) and just ten crops (8). In contrast,the wild harvest of aquatic and terrestrial species in-cludes thousands of species, habitats, and capturetechnologies. These differences will affect the resil-ience of targeted stocks—and thus the sustainabilityof the harvest—but also lead to more types of envi-ronmental impact and greater variability within eachimpact (2). For example, although greenhouse gasemissions from marine fisheries are generally lowerthan estimates from other animal protein production,emissions can vary widely depending on motorization,species, gear type, and location (9).

The additional diversity that these underassessedfoods provide—both within and between food types—offers greater opportunities for policymakers to miti-gate the environmental impacts of food production.Policy could strategically support the kinds of pro-duction most likely to minimize the trade-offs betweenenvironmental and other objectives. For example,bushmeat hunting and inland fisheries have potentiallyserious impacts on native biodiversity and the societalbenefits arising from biodiversity. However, these foodsare often a vital protein source for marginalized peopleand have extremely low impacts on water pollution orgreenhouse gas emissions compared with other foods.Only by incorporating data on these foods and asso-ciated environmental impacts into food system ac-counting will consumers be able to make fully informedchoices and policymakers to identify and evaluatetrade-offs within and across food systems. This infor-mation is requisite to managing for lower overall foodsystem impacts.

Critical LinkagesInterdependencies among food production sectorsare commonplace: manure is used to fertilize crops,land converted to crops is no longer available aspasture, and fish farms displace local wild fisheries.Some linkages are well studied and reveal the com-plexity of interactions. For example, studies of theubiquitous linkage between fed animals and their feedhave highlighted less-known results that roughly 4% ofcrops are fed to farmed seafood (8) and 27% of wild-caught fish is used as feed for farmed fish, pigs, andpoultry (4).

But few studies have comprehensively accountedfor the suite of linkages among systems, despite their

significance for the cumulative impact of food pro-duction, and more indirect linkages abound. Agricul-tural pollution limits the location and yield of inlandand coastal aquaculture (10), disease and genetic es-capes from aquaculture pens can influence the healthof wild fish stocks and vice versa (11), and landscapehomogenization in the search for more efficient pro-duction can disrupt natural pollination and potentiallydecrease yields (12). Linkages can also generate

Fig. 2. Among different nations, the proportions of foodfrom crops, livestock, milk, and eggs (warm colors) andvarious underassessed foods (cool colors) varies widely.Countries are grouped by continent or global region,and only those with greater than 10% underassessedfood are shown. The key to the three-letter countrycodes is provided in Ext. Data S2. Comm., commercial;IUU, illegal, unreported, and unregulated; Prop.,proportion; Unrep., unreported.

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win-win opportunities. For example, feeding seaweedto cows dramatically reduces methane emissions fromcattle while also potentially reducing the need toconvert new land to crop cultivation (13). Even morepoorly known are the potential linkages among dif-ferent types of underassessed foods—as when un-regulated overfishing (often by foreign fleets) spursbushmeat hunting (14) or when shrimp farming de-stroys mangroves critical as a nursery habitat forharvested wild stocks.

Connections among food sectors are likely be-coming more pervasive as commodity markets be-come fully global and production expands intonew areas, creating complex cascades of interde-pendencies. To avoid unintended negative impacts,as well as to identify and capitalize on potential win-win opportunities, requires clear, quantitative as-sessments of both positive and negative linkagesamong food systems that can, for example, helpfarmers make informed choices regarding raw ma-terial inputs and waste management. Integration ofimpacts and linkages into comprehensive assess-ments will also allow policymakers to evaluatenew production systems in the context of wider re-gional and global food systems and sustainabilityobjectives.

Only if researchers provide assessments and meth-odologies to support an integrative understanding willdecision makers be able to anticipate how and wherethe different dimensions of environmental impacts willchange under a given action. Such an approach is vital ifwe are to achieve increased production and harvestwhile decreasing the environmental impact of food. It isno longer safe to rely on natural resilience to ensuresustainable food production, given that many buffers tothe planet’s ecological limits are already close toexhausted (15), and in some regions, local limits havealready been surpassed.

Smarter Food PolicyThe global food system is too complex, diverse, andcontingent on environmental and socioeconomiccontext to allow for simple or singular policy recom-mendations. However, because food systems arelinked globally through international supply chainsand distributed environmental impacts (e.g., green-house gases), achieving sustainable food productionfor 10 billion peoplewill require global-level coordination,through mechanisms such as intergovernmental agree-ments and trade deals. Such collaboration will needto favor more environmentally efficient forms ofproduction while meeting food security and othersustainable development goals, decisions that re-quire comprehensive and balanced knowledge onthe impacts of different food production systems andlinkages among them.

Addressing these shortcomings requires threelinked approaches: First, funding organizations andresearchers should prioritize the collation, collection,and synthesis of spatially explicit primary data onunderassessed foods and underassessed impacts forwell-studied foods. New studies should be evaluated

for how much they augment existing data, and wesuggest prioritizing initial data collection and collationand synthesis of understudied foods and environ-mental impacts over ever-more refined studies of well-documented systems. For example, many tropical andarid crops (e.g., sorghum, coffee, and sugar cane) andaquatic species (e.g., inland fisheries and seaweedmariculture) are underassessed and are critical in de-veloping nations.

Importantly, including many underassessed foodsin comprehensive assessments is immediately tracta-ble because necessary data often already exist (e.g.,country-level production and global-gridded data-bases of fisheries). Rapid advances in satellite remotesensing and artificial intelligence are already beingused for monitoring biodiversity, as well as fishing,farming, and hunting activities. Where data gaps ex-ist, they should be prioritized for expanded moni-toring but could be temporarily filled by estimationor simulation. For example, remote sensing andgeographic information system data can be in-tegrated into environmental suitability models topredict bushmeat hunting patterns in Central Africa

(16). Although some of these approaches are still intheir infancy, they are improving as new data andtechnologies rapidly come online.

Second, the linkages among different foods andaspects of the food system need to be better definedand quantified. International organizations such as theFood and Agriculture Organization and other UnitedNations agencies are well placed to coordinate andlead such efforts, with the collation and provision ofexisting datasets being a priority. The quality of thesedatasets, however, critically depends on the statisticalcapacities of the reporting countries. In short, theseagencies need additional financial support if they areto better track and report linkages among foods.Existing economic and environmental methods havegreat potential to improve our understanding anddocumentation of these linkages—for example, the useof hydrological models to predict where eutrophicationwill impact downstream food production. But again, it isimportant to restate that even the most sophisticatedmodels today would omit large parts of the globalfood system because the data underpinning themare underreported.

Finally, we issue an urgent call for national andinternational policymakers to increase dialogue andthe sharing of data and even personnel among de-partments tasked with different aspects of food sys-tems. We must reverse trends toward decreased

The diversity of food systems, the range of objectivesand stakeholders, and the linkages among differentcomponents make forward-looking, proactive, andcomprehensive food policy a major challenge at all levelsfrom individuals to international organizations.

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funding for gathering national and subnational foodstatistics. Coordination and adequate staffing are vitalfor enabling comparable and comprehensive assess-ments of food’s environmental impacts, understandingtrade-offs and synergies among different objectives,and setting sustainable dietary recommendations forconsumers. For example, if all Americans followed theUS Department of Agriculture–recommended diet, USgreenhouse gas emissions from food would actuallyincrease by 12% (17). Although shifts toward alternativediet scenarios have been estimated to reduce land-use and greenhouse gases, the full suite of impacts(Ext. Data S3) and the linkages associated with feed,including fertilizer and other indirect and localizedimpacts, have not yet been accounted for in theseassessments.

The diversity of food systems, the range of objec-tives and stakeholders, and the linkages among dif-ferent components make forward-looking, proactive,and comprehensive food policy a major challenge atall levels from individuals to international organiza-tions. To make effective food policy now and to planfor future scenarios and shifting linkages among foodsectors we need a comprehensive baseline under-standing that includes all food systems, their directand indirect connections, and how these are chang-ing. Armed with this information, a wide variety of

positive outcomes becomes possible through improvingefficiency within particular food systems, favoring posi-tive over negative linkages, encouraging the consump-tion of low-impact foods, or any combination of thesestrategies. For example, governments could favor sub-sidies for low-impact or positive-linkage foods, foodcompanies could develop (andmarket) foods they knowscientifically are more environmentally efficient, andconsumers could make better-informed decisions atsupermarkets and restaurants. Some of these oppor-tunities are already occurring because of increasedawareness of the health and environmental impacts offood, but many are currently missed because of majorgaps in assessments of the impacts and linkages in foodsystems.

We ask policymakers to work toward responsiblefood production that respects the planet’s limits. Andwe call on researchers to put all foods on the same tablein even-handed environmental impact assessments.

AcknowledgmentsThe National Center for Ecological Analysis and Synthesis at theUniversity of California, Santa Barbara provided invaluable infra-structural support for this work. The Zegar Family Foundationprovided support for the working group; additional support forJ.A.G. was from the National Socio-Environmental SynthesisCenter: National Science Foundation DBI-1052875.

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