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The carbon opportunity cost of animal-sourced food production on land

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Abstract and Figures

Extensive land uses to meet dietary preferences incur a ‘carbon opportunity cost’ given the potential for carbon sequestration through ecosystem restoration. Here we map the magnitude of this opportunity, finding that shifts in global food production to plant-based diets by 2050 could lead to sequestration of 332–547 GtCO2, equivalent to 99–163% of the CO2 emissions budget consistent with a 66% chance of limiting warming to 1.5 °C. Shifting global food production to plant-based diets by 2050 can sequester 99–163% of the CO2 emissions budget towards limiting climate warming to 1.5 °C.
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1Department of Environmental Studies, New York University, New York, NY, USA. 2Animal Law and Policy Program, Harvard Law School, Cambridge, MA,
USA. 3Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR, USA. 4Department of Ecosystem Science and Sustainability,
Colorado State University, Fort Collins, CO, USA. 5Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO, USA.
Extensive land uses to meet dietary preferences incur a ‘car-
bon opportunity cost’ given the potential for carbon seques-
tration through ecosystem restoration. Here we map the
magnitude of this opportunity, finding that shifts in global
food production to plant-based diets by 2050 could lead to
sequestration of 332–547 GtCO2, equivalent to 99–163% of
the CO2 emissions budget consistent with a 66% chance of
limiting warming to 1.5 °C.
Restoration of native ecosystems, including forests, is a land-based
option for atmospheric carbon dioxide (CO2) removal1. Ecosystem
restoration is constrained largely by land requirements of food pro-
duction, the largest human use of land globally2. Food production
therefore incurs a ‘carbon opportunity cost’, that is, the potential for
natural CO2 removal via ecosystem restoration on land3,4. This cost
can vary greatly depending on the ‘potential’ or ‘native’ vegetation of
a given region and types of food produced. Animal-sourced foods
such as meat and dairy have large land footprints because animals
typically consume more food macronutrients than they produce5.
Quantifying the spatial distribution of agriculture’s cumulative car-
bon opportunity cost within this century can inform efforts to limit
global warming to 1.5 °C.
Ongoing agricultural emissions can be abated by shifts to
less-resource-intensive, plant-based diets6,7, but the potential for
cumulative CO2 removal from native vegetation regrowth in areas
occupied by animal agriculture has not previously been calculated
in a spatially explicit manner. Here we quantify the total carbon
opportunity cost of animal agricultural production to be 152.5
(94.2–207.1) gigatons of carbon (GtC) in living plant biomass across
all continents and biomes (Fig. 1 and Supplementary Table 3).
We approximated the potential for CO2 removal in soil and litter
as an additional 63 GtC (Supplementary Table 4). This estimate is
associated with large but unknown uncertainty because of a deficit
of data and the complexity of dynamics of non-living carbon pools
in restored ecosystems.
Pastures for ruminant meat and dairy production represent the
majority of the total carbon opportunity cost—72%—compared
with animal feed croplands, which suppress the remaining 28% of
native vegetation carbon (Supplementary Table 3). Potential pro-
ductivity on remaining cropland is sufficient to supply the current
global population with 78 g capita1 day1 of protein (after factoring
losses from both storage and consumer waste), an amount exceed-
ing dietary recommendations, accounting for variation in nutri-
tional requirements among demographic groups and for disparities
in food availability8.
The cumulative potential of CO2 removal on land currently
occupied by animal agriculture is comparable in order of magnitude
to the past decade of global fossil fuel emissions. The largest poten-
tial for negative emissions—74 GtC or 48% of the global total—lies
in upper-middle-income countries (Fig. 2), which will further
increase as meat and dairy production expand. This is approxi-
mately equal to the past 19 years of fossil fuel emissions in these
countries. In high-income countries, in which animal-sourced food
demand is high but plateauing8, the total carbon opportunity cost of
animal-sourced food production is 32 GtC, approximately equal to
the past 9 years of their domestic fossil fuel emissions.
Present-day pasturelands exist in areas of both native forests and
grasslands within all continents (Supplementary Table 3). Pastures
in native forest areas displace 72 GtC—accounting for 68% of pas-
tures’ carbon opportunity cost but only 22% of total pasture area
(Supplementary Table 3 and Supplementary Fig. 2). In native grass-
lands, vegetation may be partially restored by improved grazing
management9, rather than removing animals altogether, although
trade-offs remain with respect to non-CO2 ruminant emissions.
In addition, optimal grazing does not always promote restoration
because ruminants selectively browse native species10 and translo-
cate nutrients11.
To understand the potential future consequences of animal-
sourced food consumption on global CO2 budgets, we modelled
land use of three global dietary scenarios to the year 2050 rela-
tive to the present day (base year 2015). The net CO2 balance was
calculated for a business-as-usual (BAU) diet following economic
trends12, a healthier diet with approximately 70% meat reduction
globally relative to BAU13 (the EAT-Lancet Commission or ELC
diet) and a vegan (VGN) diet with no animal-sourced foods8.
The BAU diet results in land clearing, with land-use-change
emissions of 86 (68–105) GtCO2 (Fig. 3) because optimistic future
improvements in yields are insufficient to meet expected animal
feed demands11.
The ELC and VGN diets result in 332 (210 to 459) and 547 (358
to 743) total GtCO2 removal, respectively, approximately equal to
the past 9 and 16 years of fossil fuel emissions. Ecosystem soil and
litter could remove an additional 135 and 225 GtCO2 for ELC and
VGN, respectively (Supplementary Table 6), but this estimate is
highly uncertain.
Smaller future increases in crop yields would result in less land
sparing and CO2 removal from ELC and VGN diets compared with
present day: 199 and 424 GtCO2, respectively (Supplementary Table
5). However, plant-rich diets would permit even greater mitigation
compared with BAU; lower yields result in greater land-clearing
emissions of 247 GtCO2.
Ceasing fossil fuel use is necessary to limit global warming, but
CO2 removal following plant-rich dietary shifts could substantially
The carbon opportunity cost of animal-sourced
food production on land
Matthew N. Hayek 1 ✉ , Helen Harwatt2, William J. Ripple3 and Nathaniel D. Mueller 4,5
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... Altogether, the large effect of animal products on climate, land-area, and ecosystems supports the view that reducing their consumption could be an effective means to mitigate climate change (Hayek et al., 2021;Jarmul et al., 2020). Earlier research has also suggested that the relocation of croplands (Beyer et al., 2022) and increasing carbon storage in forests (Sohngen & 540 Mendelsohn, 2003) are effective ways to mitigate climate change. ...
... Harper et al., 2018;Roe et al., 2019;Daioglou et al., 2019;Daigneault et al., 2022;Roebroek et al., 2023) and the topic's policy-relevance has recently increased due to the grown interest in maintaining and enhancing land-based carbon sinks (Griscom et al., 2017;Rockström et al., 2021). Our demonstration of CLASH in section 5 highlights the model's capacity to depict several wellknown mechanisms through which land-use can contribute to climate change mitigation, including reducing the consumption 555 of animal products (Hayek et al., 2021;Jarmul et al., 2020), relocating croplands (Beyer et al., 2022) and increasing carbon storage in forests (Sohngen & Mendelsohn, 2003). ...
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The Climate-responsive Land Allocation model with carbon Storage and Harvests (CLASH) is a global land-use model that can be embedded into integrated assessment models (IAMs). It represents vegetation growth, terrestrial carbon stocks, and production from agriculture and forestry for different land-uses in a changing climate; and hence, allows the inclusion of terrestrial carbon stocks, agriculture and forestry in global climate policy analyses. All terrestrial ecosystems and their carbon dynamics are comprehensively described at a coarse resolution. Special emphasis is placed representing the world’s forests. In CLASH, vegetation growth, soil carbon stocks, agricultural yields and natural disturbance frequencies react to changing climatic conditions, emulating the dynamic global vegetation model LPJ-GUESS. Land is divided into ten biomes with six land-use classes (including forests and agricultural classes). Secondary forests are age structured. The timing of forest harvests affects forest carbon stocks; and hence, carbon storage per forest area can be increased through forest management. In addition to secondary forests, CLASH also includes primary ecosystems, cropland, and pastures. The comprehensive inclusion of all land-use classes and their main functions allows representing the global land-use competition. In this article, we present, calibrate, and validate the model, demonstrate its use, and discuss how it can be integrated into IAMs.
... The food system is responsible for a third of global anthropogenic greenhouse gas emissions and is a major source of biodiversity loss Crippa et al., 2021;Poore & Nemecek, 2018;Springmann et al., 2018). It is also the largest emitter of methanea powerful short-lived greenhouse gas which can be largely attributed to livestock farming Hayek et al., 2021). Without transforming the food system, the goal of limiting the global temperature rise to 1.5 • C would be hardly achievable even if all other sectors were to rapidly drive emissions down to net-zero Milkoreit et al., 2018;Sharpe & Lenton, 2021). ...
... Without transforming the food system, the goal of limiting the global temperature rise to 1.5 • C would be hardly achievable even if all other sectors were to rapidly drive emissions down to net-zero Milkoreit et al., 2018;Sharpe & Lenton, 2021). In particular, the shift to plant-based diets offers a cost-effective and environmentally integer solution to mitigate agricultural emissions, substantially reducing global deforestation and saving a few hundred gigatonnes of CO 2 from the atmosphere by 2050 (Brunner et al., 2018;Carlsson et al., 2022;Hayek et al., 2021;Parodi et al., 2018;Springmann et al., 2018;Xu et al., 2021). The production and consumption of meat is also linked to human health (Godfray et al., 2018), contributing to the outbreak of pandemics like Covid-19 and to increased risk of mortality due to cardiovascular diseases, cancer, and diabetes. ...
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The food system causes more than a third of the global anthropogenic greenhouse gas emissions, of which half are from livestock. Shifting towards plant-based diets could significantly reduce deforestation, protect biodiversity , and contribute to achieving the Sustainable Development Goals and Paris climate targets. Arguably, large-scale shifts in meat consumption require ambitious policy change. Yet, deep-rooted eating habits, pleasure, cultural status, and personal freedom are just a few of many obstacles to adopt ambitious demand-side policies and reduce meat consumption. Here, we hypothesize that technological innovation in meat substitutes, if effectively combined with social norm and factual informational triggers for behavioral changes, can foster positive political feedback to transform the food system. To test our hypothesis, we conducted survey experiments with citizens (N = 2590) in China and the US-the globally largest meat markets-and analyzed data using different machine learning methods. Our findings show that personal experience with novel plant-based meat substitutes strongly predicts individuals' intentions to reduce their meat consumption, eat more substitutes, and support public policies to catalyze a transition to more plant-based diets. We also find that in both countries factual and social norm information about the benefits of more plant-based diets can increase citizens' behavioral change intentions and support for meat reduction policies. Overall, however, social norm information had no significant additional effects on the outcomes compared to the simple factual information treatments. In the US, prior experience with innovative meat substitutes potentially can boost the positive effects of informational campaigns on public support for meat reduction policies. The results offer promising implications for a policy sequencing strategy to create positive political feedback and enable socio-technical tipping dynamics for sustainable food system transformation.
... If ranching-focused agriculture increases in popularity, it may improve some overly grazed or intensively cropped areas but would mean a mass program of deforestation and wild ecosystem conversion to even come close to meeting current typical grazing and feedlot beef yields, all while likely increasing methane (Eisen & Brown 2022). Studies have shown that shifts to plant-based food systems, and rewilding; freeing up grazing and feed crop land, can draw down the equivalent of 9-16 years of fossil fuel emissions (Hayek et al. 2020). ...
Agriculture is a major contributor to greenhouse gas (GHG) emissions and biodiversity loss, mostly through deforestation for the cultivation of animal feeds; enteric fermentation from ruminants like cattle, fertilizers and manure; and soil degradation from intensive farming practices. There is currently a push to transform our farming systems to attempt to alleviate the almost-assured catastrophic burden of increasing amounts of atmospheric carbon. Many forms of agriculture claim they have evolved to follow a more regenerative form of agriculture by increasing soil organic matter (SOM), thus capturing said carbon in their soils. This study reports SOM results from one veganic agriculture (VA) farm from a study period of seven years. There was an observed increase of SOM from 5.2% to 7.2%, equating to an increase of 38.46% over the study’s duration, suggesting that VA is an effective farming mechanism for increasing soil organic matter utilizing 100% plant-based regenerative practices and materials to nourish the soil. The VA farm also realized respectable yields per hectare, reporting a 46% increase in total crop production. This was all achieved by growing a diversity of plant-based crops, implementing four-year crop rotations, building soil fertility through plant-based inputs, cover cropping, and leaving the farm’s fields covered as often as possible. Additionally, by its processes, the VA farm fully eliminated the industrial chain of animal agriculture and associated land use and methane emissions, suggesting VA to be a holistically regenerative form of agriculture, in comparison to animal-based forms of any other system.
... Animal-based foods also involve tremendous land-system changes: 83% of the world's farmland is used to produce meat, aquaculture, eggs, and dairy, yet these outputs provide just 18% of all calories and 37% of all protein globally produced (Poore and Nemecek, 2018). In the United States, where 41% of all land in the contiguous states is used for livestock (pasture and cropland) (Merrill and Leatherby, 2018 ), there is great opportunity if the diet-land-climate change nexus is recognized (Eshel et al., 2019) due to livestock's enormous carbon opportunity cost (Hayek et al., 2021). As the main driver of natural habitat loss worldwide and the largest anthropogenic land use type, the production of animal-based Saha . ...
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Building on literature from political science and psychology, I argue that political attention on animals and animal-friendly political candidates cause voter backlash. I test this using two different kinds of experiments with large, representative samples. I ask respondents to consider political candidates running for office in a U.S. presidential primary context. I find that, overall, political attention on the need to reduce meat consumption for environmental reasons caused voter backlash compared to both a control condition and attention on the need to reduce reliance on gasoline-powered vehicles (also for environmental reasons). But, the heterogeneous effects of partisan identification were strong: voter backlash was mainly driven by Republicans and Democrats were neutral. Surprisingly, candidates who put attention on farm animal rights during elections faced no voter backlash from Republicans or Democrats. Animal-friendly candidates, particularly Black women and Latinas, with attributes that demonstrate personal concern for farm animals and strong support for animal rights generally fared very well in elections, receiving large boosts in voter support. This work launches a research agenda in political psychology that “brings the animal in” to politics.
... A new green business model involving farmers and producers in carbon sequestration could importantly contribute to achieve the carbon neutrality objective, as exposed in the Farm to Fork strategy (European Commission, 2020). A shift to plant-based diets, has great potential for cumulative CO 2 mitigation (Hayek et al., 2021), as well as can achieve substantial reductions in other impacts such as eutrophication or acidification (Takacs et al., 2022), despite the disadvantage of a highly-energy intensive profile. Additionally, the development of novel products more adaptative to climate change and biotic and abiotic stresses, such as algae, can reduce the ongoing food impacts (Loboguerrero et al., 2019). ...
Carbon dioxide removal (CDR) technologies are considered essential to accomplish the Paris Agreement targets. Given the important contribution of the food sector to climate change, this study aims to investigate the role of two carbon capture and utilization (CCU) technologies in decarbonizing the production of spirulina, an algae product commonly consumed for its nutritional characteristics. The proposed scenarios considered the replacement of synthetic food-grade CO2 in Arthrospira platensis cultivation (BAU scenario) with CO2 from beer fermentation (BRW) and CO2 from DACC (direct air carbon capture) (SDACC), representing two alternatives with great potential in the short and medium-long term, respectively. The methodology follows the Life Cycle Assessment guidelines, considering a cradle-to-gate scope and a functional unit equivalent to the annual production of spirulina in a Spanish artisanal plant. Results showed a better environmental performance of both CCU scenarios as compared to BAU, reaching a reduction of greenhouse gas (GHG) emissions of 52 % in BRW and of 46 % in SDACC. Although the brewery CCU offers a deeper carbon mitigation of spirulina production, the process cannot reach net zero GHG emissions due to residual burdens across the supply chain. In comparison, the DACC unit could potentially supply both the CO2 needed in spirulina production and work as a CDR to compensate residual emissions, which opens the door for further research on its technical and economic feasibility in the food sector.
... Notably, dietary change has considerable mitigation potential and would not necessarily require new technology or innovation. For example, reducing the intake of animal-sourced foods (ASF) could yield important climate benefits [3][4][5][6][7][8][9][10] , while contributing to planetary stability regarding land use, biogeochemical cycles, biodiversity and water use 4,11 , as well as improving public health outcomes 6,7,12 . Relative to plant-based foods (PBF), ASF production emits appreciably more carbon per gram 3 and accounts for the majority of total food production emissions 9 . ...
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Potential external cost savings associated with the reduction of animal-sourced foods remain poorly understood. Here we combine life cycle assessment principles and monetarization factors to estimate the monetary worth of damage to human health and ecosystems caused by the environmental impacts of food production. We find that, globally, approximately US$2 of production-related external costs were embedded in every dollar of food expenditure in 2018—corresponding to US$14.0 trillion of externalities. A dietary shift away from animal-sourced foods could greatly reduce these ‘hidden’ costs, saving up to US$7.3 trillion worth of production-related health burden and ecosystem degradation while curbing carbon emissions. By comparing the health effects of dietary change from the consumption versus the production of food, we also show that omitting the latter means underestimating the benefits of more plant-based diets. Our analysis reveals the substantial potential of dietary change, particularly in high and upper-middle-income countries, to deliver socio-economic benefits while mitigating climate change.
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A growing literature in Life Cycle Assessment seeks to better inform consumers, food policymakers, food supply chain actors, and other relevant stakeholders about how individual foods contribute to sustainable diets. One major challenge involves accurately capturing potential trade-offs between nutritional provision and environmental impacts associated with food production. In response, food system sustainability literature has turned increasingly to nutritional Life Cycle Assessment, which assesses the environmental footprints of different foods while accounting for nutritional value. Here we provide examples that show how environmental footprints based on a priority micronutrient-focused functional unit can provide nutritionally meaningful insights about the complexities involved in sustainable food systems. We reinforce the idea that there are limitations in using single-value nutrition-environment scores to inform food guidance, as they do not adequately capture the complex multi-dimensionality and variation involved in healthy and sustainable food systems. In our discussion we highlight the need for future agri-food sustainability assessments to pay attention to regional nutritional and environmental variation within and between commodities, and to better interpret trade-offs involved in food substitutions.
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The aim of this study was to investigate how consumers ( n = 2,171) originated from South-Western Europe (Italy, Portugal, and Spain) perceive cultured “meat” (CM) and if their demographic characteristics (origin, gender, age, education, occupation, and meat consumption) are related to their willingness to try (WTT), to regularly eat (WTE) and to pay (WTP) for CM. We found the current respondents had an initially positive attitude towards CM: 49% of them perceived CM as “promising and/or acceptable” and 23% “fun and/or intriguing” whereas 29% considered it as “absurd and/or disgusting”. In addition, 66 and 25% would be willing and not willing to try CM, respectively. However, 43% had no WTE for CM and, 94% would not pay more for CM compared to conventional meat. Age and especially occupation were good indicators of consumer acceptance of CM. Respondents of 18–30 years of age had the highest acceptance. Respondents outside the meat sector had the highest WTE and people working within the meat sector had the lowest WTE, scientists (within or outside the meat sector) had the highest WTT, people not scientists but within the meat sector had the lowest WTT. Additionally, we found that men are more likely to accept CM than women, Spanish-speaking consumers had the highest WTT and WTE, people with vegan and vegetarian diets may pay more for CM but generally no more than for conventional meat. The perceptions that CM may be more eco-friendly, ethical, safe and healthy than conventional meat, and to a lower extent, the perception that current meat production causes ethical and environmental problems are likely to be major motives for the current respondents to try, regularly eat and pay for CM. On the opposite, lower perceptions of CM benefits and of conventional meat weaknesses more generally, plus emotional resistance towards CM are main barriers to accept CM.
Objective: To determine the effectiveness of the "Plants for Joints" multidisciplinary lifestyle program in patients with metabolic syndrome-associated osteoarthritis (MSOA). Design: Patients with hip or knee MSOA were randomized to the intervention or control group. The intervention group followed a 16-week program in addition to usual care based on a whole food plant-based diet, physical activity and stress management. The control group received usual care. The patient-reported Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC) total score (range 0-96) was the primary outcome. Secondary outcomes included other patient-reported, anthropometric and metabolic measures. An intention-to-treat analysis with a linear-mixed model adjusted for baseline values was used to analyse between-group differences. Results: Of the 66 people randomized, 64 completed the study. Participants (84% female) had a mean (SD) age of 63 (6) years and BMI of 33 (5) kg/m2. After 16 weeks the intervention group (n = 32) had a mean 11-point larger improvement in WOMAC-score (95% CI 6 to 16; p=0.0001) compared to the control group. The intervention group also lost more weight (-5kg), fat mass (-4kg) and waist circumference (-6cm) compared to the control group. PROMIS® fatigue, pain interference, CRP, HbA1c, fasting glucose and LDL improved in the intervention versus the control group, while other PROMIS® measures, blood pressure, HDL and triglycerides did not differ significantly between the groups. Conclusion: The "Plants for Joints" lifestyle program reduced stiffness, relieved pain and improved physical function in people with hip or knee MSOA compared to usual care.
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Wild herbivore populations are declining in many African savannas, which is related to replacement by livestock (mainly cattle) and the loss of megaherbivores. Although some livestock management practices may be compatible with the conservation of native savanna biodiversity, the sustainability of these integrated wild herbivore/livestock management practices is unknown. For instance, how will these herbivore mixes influence key processes for the long-term functioning of savanna ecosystems, such as soil carbon, nitrogen and phosphorus pools and cycling? The Kenya Long-term Exclosure Experiment studies the ecosystem consequences of manipulating the presence and absence of wild herbivores and cattle at moderate densities in a ‘black cotton’ savanna. Here we show that after 20 years, cattle presence decreased total soil carbon and nitrogen pools, while the presence of megaherbivores (mainly elephants) increased these pools and even reversed the negative effects of cattle. Our results suggest that a mix of cattle at moderate densities and wild herbivores can be sustainable, provided that the assemblage of wild herbivores includes the largest species. Cattle are replacing wildlife in many African savannas. This field study finds that wild megaherbivores, such as elephants, increased soil carbon and nitrogen, and hence soil fertility, normally lost when only cattle are present.
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Land-use changes are critical for climate policy because native vegetation and soils store abundant carbon and their losses from agricultural expansion, together with emissions from agricultural production, contribute about 20 to 25 per cent of greenhouse gas emissions1,2. Most climate strategies require maintaining or increasing land-based carbon³ while meeting food demands, which are expected to grow by more than 50 per cent by 20501,2,4. A finite global land area implies that fulfilling these strategies requires increasing global land-use efficiency of both storing carbon and producing food. Yet measuring the efficiency of land-use changes from the perspective of greenhouse gas emissions is challenging, particularly when land outputs change, for example, from one food to another or from food to carbon storage in forests. Intuitively, if a hectare of land produces maize well and forest poorly, maize should be the more efficient use of land, and vice versa. However, quantifying this difference and the yields at which the balance changes requires a common metric that factors in different outputs, emissions from different agricultural inputs (such as fertilizer) and the different productive potentials of land due to physical factors such as rainfall or soils. Here we propose a carbon benefits index that measures how changes in the output types, output quantities and production processes of a hectare of land contribute to the global capacity to store carbon and to reduce total greenhouse gas emissions. This index does not evaluate biodiversity or other ecosystem values, which must be analysed separately. We apply the index to a range of land-use and consumption choices relevant to climate policy, such as reforesting pastures, biofuel production and diet changes. We find that these choices can have much greater implications for the climate than previously understood because standard methods for evaluating the effects of land use4–11 on greenhouse gas emissions systematically underestimate the opportunity of land to store carbon if it is not used for agriculture.
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Background Sustainable diets are intended to address the increasing health and environmental concerns related to food production and consumption. Although many candidates for sustainable diets have emerged, a consistent and joint environmental and health analysis of these diets has not been done at a regional level. Using an integrated health and environmental modelling framework for more than 150 countries, we examined three different approaches to sustainable diets motivated by environmental, food security, and public health objectives. Methods In this global modelling analysis, we combined analyses of nutrient levels, diet-related and weight-related chronic disease mortality, and environmental impacts for more than 150 countries in three sets of diet scenarios. The first set, based on environmental objectives, replaced 25–100% of animal-source foods with plant-based foods. The second set, based on food security objectives, reduced levels of underweight, overweight, and obesity by 25–100%. The third set, based on public health objectives, consisted of four energy-balanced dietary patterns: flexitarian, pescatarian, vegetarian, and vegan. In the nutrient analysis, we calculated nutrient intake and changes in adequacy based on international recommendations and a global dataset of nutrient content and supply. In the health analysis, we estimated changes in mortality using a comparative risk assessment with nine diet and weight-related risk factors. In the environmental analysis, we combined country-specific and food group-specific footprints for greenhouse gas emissions, cropland use, freshwater use, nitrogen application, and phosphorus application to analyse the relationship between the health and environmental impacts of dietary change. Findings Following environmental objectives by replacing animal-source foods with plant-based ones was particularly effective in high-income countries for improving nutrient levels, lowering premature mortality (reduction of up to 12% [95% CI 10–13] with complete replacement), and reducing some environmental impacts, in particular greenhouse gas emissions (reductions of up to 84%). However, it also increased freshwater use (increases of up to 16%) and had little effectiveness in countries with low or moderate consumption of animal-source foods. Following food-security objectives by reducing underweight and overweight led to similar reductions in premature mortality (reduction of up to 10% [95% CI 9–11]), and moderately improved nutrient levels. However, it led to only small reductions in environmental impacts at the global level (all impacts changed by <15%), with reduced impacts in high-income and middle-income countries, and increased resource use in low-income countries. Following public health objectives by adopting energy-balanced, low-meat dietary patterns that are in line with available evidence on healthy eating led to an adequate nutrient supply for most nutrients, and large reductions in premature mortality (reduction of 19% [95% CI 18–20] for the flexitarian diet to 22% [18–24] for the vegan diet). It also markedly reduced environmental impacts globally (reducing greenhouse gas emissions by 54–87%, nitrogen application by 23–25%, phosphorus application by 18–21%, cropland use by 8–11%, and freshwater use by 2–11%) and in most regions, except for some environmental domains (cropland use, freshwater use, and phosphorus application) in low-income countries. Interpretation Approaches for sustainable diets are context specific and can result in concurrent reductions in environmental and health impacts globally and in most regions, particularly in high-income and middle-income countries, but they can also increase resource use in low-income countries when diets diversify. A public health strategy focused on improving energy balance and dietary changes towards predominantly plant-based diets that are in line with evidence on healthy eating is a suitable approach for sustainable diets. Updating national dietary guidelines to reflect the latest evidence on healthy eating can by itself be important for improving health and reducing environmental impacts and can complement broader and more explicit criteria of sustainability. Funding Wellcome Trust, EAT, CGIAR, and British Heart Foundation.
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The global impacts of food production Food is produced and processed by millions of farmers and intermediaries globally, with substantial associated environmental costs. Given the heterogeneity of producers, what is the best way to reduce food's environmental impacts? Poore and Nemecek consolidated data on the multiple environmental impacts of ∼38,000 farms producing 40 different agricultural goods around the world in a meta-analysis comparing various types of food production systems. The environmental cost of producing the same goods can be highly variable. However, this heterogeneity creates opportunities to target the small numbers of producers that have the most impact. Science , this issue p. 987
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The need for more sustainable production and consumption of animal‐source food is central to the achievement of the sustainable development goals: within this context, wise use of land is a core challenge and concern. A key question in feeding the future world is: how much animal‐source food should we eat? We demonstrate that livestock raised under the circular economy concept could provide a significant, non‐negligible part (9‐23g/per capita) of our daily protein needs (~50‐60 g/per capita). This livestock then would not consume human‐edible biomass, such as grains, but mainly convert leftovers from arable land and grass resources into valuable food, implying that production of livestock feed is largely decoupled from arable land. The availability of these biomass streams for livestock then determines the boundaries for livestock production and consumption. Under this concept, the competition for land for feed or food would be minimized and compared to no animal‐source food, including some animal‐source food in the human diet could free up about one quarter of global arable land. Our results also demonstrate that restricted growth in consumption of animal‐source food in Africa and Asia would be feasible under these boundary conditions, while reductions in the rest of the world would be necessary to meet land use sustainability criteria. Managing this expansion and contraction of future consumption of animal‐source food is essential for achieving sustainable nutrition security. This article is protected by copyright. All rights reserved.
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Significance With a third of all food production lost via leaky supply chains or spoilage, food loss is a key contributor to global food insecurity. Demand for resource-intensive animal-based food further limits food availability. In this paper, we show that plant-based replacements for each of the major animal categories in the United States (beef, pork, dairy, poultry, and eggs) can produce twofold to 20-fold more nutritionally similar food per unit cropland. Replacing all animal-based items with plant-based replacement diets can add enough food to feed 350 million additional people, more than the expected benefits of eliminating all supply chain food loss.
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Globally, demand for food animal products is rising. At the same time, we face mounting, related pressures including limited natural resources, negative environmental externalities, climate disruption, and population growth. Governments and other stakeholders are seeking strategies to boost food production efficiency and food system resiliency, and aquaculture (farmed seafood) is commonly viewed as having a major role in improving global food security based on longstanding measures of animal production efficiency. The most widely used measurement is called the 'feed conversion ratio' (FCR), which is the weight of feed administered over the lifetime of an animal divided by weight gained. By this measure, fed aquaculture and chickens are similarly efficient at converting feed into animal biomass, and both are more efficient compared to pigs and cattle. FCR does not account for differences in feed content, edible portion of an animal, or nutritional quality of the final product. Given these limitations, we searched the literature for alternative efficiency measures and identified 'nutrient retention', which can be used to compare protein and calories in feed (inputs) and edible portions of animals (outputs). Protein and calorie retention have not been calculated for most aquaculture species. Focusing on commercial production, we collected data on feed composition, feed conversion ratios, edible portions (i.e. yield), and nutritional content of edible flesh for nine aquatic and three terrestrial farmed animal species. We estimate that 19% of protein and 10% of calories in feed for aquatic species are ultimately made available in the human food supply, with significant variation between species. Comparing all terrestrial and aquatic animals in the study, chickens are most efficient using these measures, followed by Atlantic salmon. Despite lower FCRs in aquaculture, protein and calorie retention for aquaculture production is comparable to livestock production. This is, in part, due to farmed fish and shrimp requiring higher levels of protein and calories in feed compared to chickens, pigs, and cattle. Strategies to address global food security should consider these alternative efficiency measures.
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Carbon stocks in vegetation have a key role in the climate system. However, the magnitude, patterns and uncertainties of carbon stocks and the effect of land use on the stocks remain poorly quantified. Here we show, using state-of-the-art datasets, that vegetation currently stores around 450 petagrams of carbon. In the hypothetical absence of land use, potential vegetation would store around 916 petagrams of carbon, under current climate conditions. This difference highlights the massive effect of land use on biomass stocks. Deforestation and other land-cover changes are responsible for 53-58% of the difference between current and potential biomass stocks. Land management effects (the biomass stock changes induced by land use within the same land cover) contribute 42-47%, but have been underestimated in the literature. Therefore, avoiding deforestation is necessary but not sufficient for mitigation of climate change. Our results imply that trade-offs exist between conserving carbon stocks on managed land and raising the contribution of biomass to raw material and energy supply for the mitigation of climate change. Efforts to raise biomass stocks are currently verifiable only in temperate forests, where their potential is limited. By contrast, large uncertainties hinder verification in the tropical forest, where the largest potential is located, pointing to challenges for the upcoming stocktaking exercises under the Paris agreement.
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Significance Most nations recently agreed to hold global average temperature rise to well below 2 °C. We examine how much climate mitigation nature can contribute to this goal with a comprehensive analysis of “natural climate solutions” (NCS): 20 conservation, restoration, and/or improved land management actions that increase carbon storage and/or avoid greenhouse gas emissions across global forests, wetlands, grasslands, and agricultural lands. We show that NCS can provide over one-third of the cost-effective climate mitigation needed between now and 2030 to stabilize warming to below 2 °C. Alongside aggressive fossil fuel emissions reductions, NCS offer a powerful set of options for nations to deliver on the Paris Climate Agreement while improving soil productivity, cleaning our air and water, and maintaining biodiversity.