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Reducing food s environmental impacts through producers ...

SUSTAINABILITYR educing food s environmentalimpacts through producersand consumersJ. Poore1,2*and T. Nemecek3 Food s environmental impacts are created by millionsof diverse producers . To identify solutionsthat are effective under this heterogeneity, we consolidated data covering five environmentalindicators; 38,700 farms; and 1600 processors, packaging types, and retailers. Impact can vary50-fold among producers of the same product, creating substantial mitigation , mitigation is complicated by trade-offs, multiple ways for producers to achieve lowimpacts, and interactions throughout the supply chain. producers have limits on how far they canreduce impacts . Most strikingly, impacts of the lowest-impact animal products typically exceedthose of vegetable substitutes, providing new evidence for the importance of dietary , our findings support an approach where producers monitor their own impacts ,flexibly meet environmental targets by choosing from multiple practices, and communicate theirimpacts to current diets and production prac-tices, feeding billion people is degrad-ing terrestrial and aquatic ecosystems,depleting water resources, and drivingclimate change (1,2).

global production. We then used randomiza-tion to capture variance at all stages of the supply chain (17). We validated the global representativeness of our sample by comparing average and 90th-percentile yields to Food and Agriculture Or-ganization (FAO) data (4), which reconcile to within ±10% for most crops. Using FAO food

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1 SUSTAINABILITYR educing food s environmentalimpacts through producersand consumersJ. Poore1,2*and T. Nemecek3 Food s environmental impacts are created by millionsof diverse producers . To identify solutionsthat are effective under this heterogeneity, we consolidated data covering five environmentalindicators; 38,700 farms; and 1600 processors, packaging types, and retailers. Impact can vary50-fold among producers of the same product, creating substantial mitigation , mitigation is complicated by trade-offs, multiple ways for producers to achieve lowimpacts, and interactions throughout the supply chain. producers have limits on how far they canreduce impacts . Most strikingly, impacts of the lowest-impact animal products typically exceedthose of vegetable substitutes, providing new evidence for the importance of dietary , our findings support an approach where producers monitor their own impacts ,flexibly meet environmental targets by choosing from multiple practices, and communicate theirimpacts to current diets and production prac-tices, feeding billion people is degrad-ing terrestrial and aquatic ecosystems,depleting water resources, and drivingclimate change (1,2).

2 It is particularlychallenging to find solutions that are effectiveacross the large and diverse range of producersthat characterize the agricultural sector. Morethan 570 million farms produce in almost all theworld sclimatesandsoils(3), each using vastlydifferent agronomic methods; average farm sizesvary from ha in Bangladesh to 3000 ha inAustralia (3); average mineral fertilizer use rangesfrom 1 kg of nitrogen per ha in Uganda to 300 kgin China (4); and although four crops provide halfof the world s food calories (4), more than 2 milliondistinct varieties are recorded in seed vaults (5).Further, products range from minimally to heavilyprocessed and packaged, with 17 of every 100 kg offood produced transported internationally, increas-ingto50kgfornutsand56kgforoils(4 ).Previous studies have assessed aspects of thisheterogeneity by using geospatial data sets (6 8),but global assessments using the inputs, outputs,and practices of actual producers have been lim-ited by data.

3 The recent rapid expansion of thelife cycle assessment (LCA) literature is providingthis information by surveying producers aroundthe world. LCA then uses models to translate pro-ducer data into environmental impacts with suf-ficient accuracy for most decision-making (9 11).To date, efforts to consolidate these data or buildnew large-scale data sets have covered greenhousegas (GHG) emissions only (8,12,13), agricultureonly (13 16), small numbers of products (8,14 16),and predominantly Western European producers (12 16) and have not corrected for important meth-odological differences between LCAs (12 16). Here,we present a globally reconciled and methodolog-ically harmonized database on the variation in food smultiple impacts . Our results show the need forfar-reaching changes in how food senvironmentalimpacts are managed and the multi-indicatorglobal databaseWe derived data from a comprehensive meta-analysis, identifying 1530 studies for potentialinclusion, which were supplemented with addi-tional data received from 139 authors.

4 Studieswere assessed against 11 criteria designed tostandardize methodology, resulting in 570 suit-able studies with a median reference year of2010 (17).The data set covers ~38,700 commer-ciallyviable farms in 119 countries (fig. S2) and40 products representing ~90% of global pro-tein and calorie consumption. It covers five im-portant environmental impact indicators (18):land use; freshwater withdrawals weighted bylocal water scarcity; and GHG, acidifying, andeutrophying emissions. For crops, yield repre-sents output for a single harvest. Land use in-cludes multicropping (up to four harvests peryear), fallow phases (uncultivated periods be-tween crops), and economic allocation to cropcoproducts such as straw. This makes it a stron-ger indicator of both farm productivity andfood security than system we assess begins with inputs (theinitial effect of producer choice) and ends at re-tail (the point of consumer choice) (fig. S1). Foreach study, we recorded the inventory of out-puts and inputs (including fertilizer quantityand type, irrigation use, soil, and climatic con-ditions).

5 Where data were not reported, for ex-ample, on climate, we used study coordinatesand spatial data sets to fill gaps. We recordedenvironmental impacts at each stage of the sup-ply chain. For GHG emissions, we further disag-gregated the farm stage into 20 emission then used the inventory to recalculate allmissing emissions. For nitrate leaching andaquaculture, we developed new models for thisstudy (17).Studies included provided ~1050 estimatesof postfarm processes. To fill gaps in process-ing, packaging, or retail, we used additionalmeta-analyses of 153 studies providing 550 ob-servations. Transport and losses were includedfrom global data sets. Each observation wasweighted by the share of national production itrepresents, and each country by its share ofglobal production . We then used randomiza-tion to capture variance at all stages of thesupply chain (17).We validated the global representativeness ofour sample by comparing average and 90th-percentile yields to Food and Agriculture Or-ganization (FAO) data (4), which reconcile towithin 10% for most crops.

6 Using FAO foodbalance sheets (4), we scaled up our sample arable land and freshwater withdrawalsreconcile to FAO estimates. Emissions from de-forestation and agricultural methane fall withinranges of independent models (17). environmental impacts of the entirefood supply chainToday s food supply chain creates ~ billionmetric tons of carbon dioxide equivalents (CO2eq),26% of anthropogenic GHG emissions. A billion metric tons of CO2eq (5%) are causedby nonfood agriculture and other drivers of de-forestation (17). Food production creates ~32%of global terrestrial acidification and ~78% ofeutrophication. These emissions can fundamen-tally alter the species composition of naturalecosystems, Reducing biodiversity and ecologicalresilience (19). The farm stage dominates, rep-resenting 61% of food sGHGemissions(81%including deforestation), 79% of acidification,and 95% of eutrophication (table S17).Today s agricultural system is also incrediblyresource intensive, covering ~43% of the world sice- and desert-free land.

7 Of this land, ~87% isfor food and 13% is for biofuels and textile cropsor is allocated to nonfood uses such as wool andleather. We estimate that two-thirds of freshwaterwithdrawals are for irrigation. However, irriga-tion returns less water to rivers and groundwaterthan industrial and municipal uses and pre-dominates in water-scarce areas and times ofthe year, driving 90 to 95% of global scarcity-weighted water use (17).Highly variable and skewedenvironmental impactsWe now group products by their primary dietaryrole and express impacts per unit of primarynutritional benefit (Fig. 1 and fig. S3). Immedi-ately apparent in our results is the high variationin impact among both products and GHG emissions of beefare 105 kg of CO2eq per 100 g of protein, andRESEARCHP ooreet al.,Science360, 987 992 (2018)1 June 20181of61 Department of Zoology, University of Oxford, New RadcliffeHouse, Oxford OX2 6GG, of Geography and theEnvironment, University of Oxford, South Parks Road, OxfordOX1 3QY, , Agroecology and Environment ResearchDivision, LCA Research Group, CH-8046 Z rich, Switzerland.

8 *Corresponding author. Email: 22 February 2019. See Erratum. on February 26, 2019 from land use (area multiplied by years occupied) is370 m2 year. These values are 12 and 50 timesgreater than 10th-percentile dairy beef impacts (which we report separately given that its pro-duction is tied to milk demand). Tenth-percentileGHG emissions and land use of dairy beef arethen 36 and 6 times greater than those of variation within and between protein-richproducts is also manifest in acidification, eutro-phication, and water the major crops wheat, maize, and rice,90th-percentileimpactsaremorethanth reetimesgreater than 10th-percentile impacts on all fiveindicators. Within major growing areas for thesecrops (the Australian wheat belt, the cornbelt, and the Yangtze river basin), land use be-comes less variable, but we observe the samehigh levels of variation in all other variability, even among producers in similargeographic regions, implies substantial potentialto reduce environmental impacts and enhanceproductivity in the food many products, impacts are skewed byproducers with particularly high impacts .

9 Thiscreates opportunities for targeted mitigation,making an immense problem more example, for beef originating from beef herds,the highest-impact 25% of producers represent56% of the beef herd sGHGemissionsand61%ofthe land use (an estimated billion metric tonsof CO2eq and 950 million ha of land, primarilypasture). Across all products, 25% of producerscontribute on average 53% of each product senvi-ronmentalimpact( ).Forscarcity-weightedfreshwater withdrawals, the skew is particular-ly pronounced: Producing just 5% of the world sfood calories creates ~40% of the environmentalburden. We will now explore how to access thesemitigation opportunities through through producersEnable producers to monitormultiple impactsThe first step in mitigation is estimating pro-ducer impacts . Prior research [ , (7, 8, 14)] hassuggested that readily measurable proxies pre-dict farm-stage impacts , avoiding the need fordetailed assessment. From our larger data set,which includes more practices and geographiesthan prior studies, we assess the predictive powerof common proxies, including crop yield, nitro-gen use efficiency, milk yield per cow, liveweightgain, pasture area, and feed conversion most proxies significantly covary withimpact, they make poor predictors when usedalone, explaining little of the variation amongfarms (coefficient of determinationR2=0to27%in 47 of 48 proxy-impact combinations assessed)(fig.)

10 S4).Prior research has also suggested using oneimpact indicator to predict others (20). We findweakly positive and sometimes negative relation-ships between indicators. For similar productsglobally, correlations between indicators are low(R2= 0 to 30% in 26 of 32 impact-impact com-binations assessed) (fig. S4). Pork, poultry meat,Pooreet al.,Science360, 987 992 (2018)1 June 20182of6100g proteinBeef (beef herd)724205042 164 Lamb & Mutton757122030 185 Beef (dairy herd) (farmed) (farmed) (flooded) & Rye (Bread) (Meal) & unitBeer (5% ABV) ( ABV) servingDark Chocolate (50g) (15g, 1 cup) 2550750510150246 Land Use(m2year)GHG Emissions(kg CO2eq) (g SO2eq)Eutroph.(g PO43 eq)050100075150075150050100 Scty. Water(kL eq) 1. Estimated global variation in GHG emissions, land use, terrestrial acidification,eutrophication, and scarcity-weighted freshwater withdrawals, within and between40 major foods.


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