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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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... Avoiding such land-use change is one of the key levers of natural climate change mitigation (Bossio et al. 2020). Even when existing pastureland and cropland are used to produce livestock feed, there is a carbon opportunity cost because restoration of native ecosystems could help remove substantial CO 2 from the atmosphere (Hayek et al. 2021, Poore & Nemecek 2018. Some of the GHG emissions from ruminant production systems can be offset by land-based carbon sequestration, for instance, through certain types of silvo-agro-forestry systems or intensive rotational grazing (Cusack et al. 2021). ...
... The previous sections have shown that current meat consumption levels are not compatible with sustainable food systems. At the global level, meat demand continues to grow quite rapidly, which could have disastrous consequences for planetary health over the next few decades (Hayek et al. 2021, Springmann et al. 2018a, Williams et al. 2021. At the same time, meat is an integral part of our food system that can help reduce poverty and widespread nutritional deficiencies, especially in low-and middle-income countries. ...
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Meat has become a controversial topic in public debates, as it involves multiple sustainability dimensions. Here, we review global meat consumption trends and the various sustainability dimensions involved, including economic, social, environmental, health, and animal welfare issues. Meat has much larger environmental and climate footprints than plant-based foods and can also be associated with negative health effects. Technological options can help to increase the sustainability of meat production, but changes in consumption are required as well. At least in high-income countries, where people consume a lot of meat on average, notable reductions will be important. However, vegetarian lifestyles for all would not necessarily be the best option. Especially in low-income countries, nutritious plant-based foods are not available or affordable year-round. Also, livestock production is an important source of income for many poor households. More research is needed on how to promote technological and behavioral changes while managing sustainability trade-offs. Expected final online publication date for the Annual Review of Resource Economics, Volume 14 is October 2022. Please see for revised estimates.
... Regardless of the management system used, shifting to slower-growing breeds, which have different nutrition requirements, would affect indirect land use via their unique nutrient requirements, hence the total quantity of crops required. Pastures and croplands for raising animals incur opportunity costs for production, potentially displacing forest habitats, ecosystem carbon [39] and biodiversity [40]. Total land-use requirements for poultry must account for both direct land use for the chickens themselves and indirect land use for their feed production. ...
... Although birds raised on pasture can move freely all or part of the day whether in a fenced-off area or the open field, chickens face the risk of natural predation by hawks or snakes [38]. Furthermore, additional land for raising chickens on pasture as well as croplands will potentially damage surrounding environments, disrupt local forest habitats and wildlife, and displace ecosystem carbon [39] and biodiversity [40]. Biodiversity loss can negatively affect human wellbeing, leading to further unintended consequences [25]. ...
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In 2018, over nine billion chickens were slaughtered in the United States. As the demand for chickens increases, so too have concerns regarding the welfare of the chickens in these systems and the damage such practices cause to the surrounding ecosystems. To address welfare concerns, there is large-scale interest in raising chickens on pasture and switching to slower-growing, higher-welfare breeds as soon as 2024. We created a box model of US chicken demographics to characterize aggregate broiler chicken welfare and land-use consequences at the country scale for US shifts to slower-growing chickens, housing with outdoor access, and pasture management. The US produces roughly 20 million metric tons of chicken meat annually. Maintaining this level of consumption entirely with a slower-growing breed would require a 44.6%–86.8% larger population of chickens and a 19.2%–27.2% higher annual slaughter rate, relative to the current demographics of primarily ‘Ross 308’ chickens that are slaughtered at a rate of 9.25 billion per year. Generating this quantity of slower-growing breeds in conventional concentrated animal feeding operations (CAFO) would require 90 582–98 687 km ² , an increase of 19.9–30.6% over the 75 577 km ² of land used for current production of Ross 308. Housing slower-growing breeds on pasture, the more individually welfare-friendly option, would require 108 642–121 019 km ² , a 43.8–60.1% increase over current land use. Allowing slower-growing breeds occasional outdoor access is an intermediate approach that would require 90 691–98 811 km ² , an increase of 20–30.7% of the current land use, a very minor increase of land relative to managing slower-growing breeds in CAFOs. In sum, without a drastic reduction in consumption, switching to alternative breeds will lead to a substantial increase in the number of individuals killed each year, an untenable increase in land use, and a possible decrease in aggregate chicken welfare at the country-level scale. Pasture-based management requires substantial additional land use. These results demonstrate constraints and trade-offs in animal welfare, environmental conservation and food animal consumption, while highlighting opportunities for policies to mitigate impacts in an integrated manner using a One Health approach.
... Finally, changes in behavior, including personal vehicle use and reduced meat consumption could result in large emissions cuts (59,60), though many climate-relevant behaviors are heavily tied to cultural practices. There is evidence that at least some social norms (like naming conventions) can change quickly (61), but habitual practices like meat consumption and personal vehicle use are deeply entrenched (62)(63)(64). ...
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Human activities have caused global temperatures to increase by 1.25°C, and the current emissions trajectory suggests that we will exceed 1.5°C in less than 10 years. Though the growth rate of global CO2 emissions has slowed and many countries have strengthened their emissions targets, current mid-century net-zero goals are insufficient to limit global warming to 1.5°C above pre-industrial temperatures. The primary barriers to the achievement of a 1.5°C-compatible pathway are not geophysical, but rather reflect inertia in our political and technological systems. Both political and corporate leadership are needed to overcome this inertia, supported by increased societal recognition of the need for system-level and individual lifestyle changes. The available evidence does not yet indicate that the world has seriously committed to achieving the 1.5°C goal.
... Nevertheless, if soil organic carbon (SOC) changes are considered, the C-footprint of milk produced by Latxa breed farming systems can be significantly reduced, offseting GHG emissions, on average, about 55% (Batalla et al. 2015), of the total C-footprint. Last, but not least, in the light of pledges calling for afforestation of pastoral lands (e.g., mountain areas) as a means of mitigating climate change (e.g., Harwatt et al. 2020;Hayek et al. 2021), it is important to note that the resultant changes in C stocks or Table 1 Mean values and standard deviations for ecological indicators. a,b Means with different superscripts in the same row indicate statistically significant differences (P ≤ 0.05) between treatments (exclusion, grazing). ...
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Pastoral systems face increasing pressure from competing global markets, food sector industrialization, and new policies such as Europe’s post-2020 Common Agriculture Policy. This pressure threatens the use of extensive sheep-grazing systems in mountain areas of low productivity but high natural value. Using information gathered at a long-term research setting in a mountainous area of the Basque Country (northern Spain), we assessed the multiple benefits of extensive dairy sheep grazing systems from multiple perspectives using indicators pertaining to ecological, socio-economic, and food quality domains. In this way, we address the benefits that would be lost if sheep grazing abandonment persists in mountain regions. Our results show that the benefits of extensive dairy sheep grazing in the research area include the production of healthy and high-quality foods and multiple ecological benefits including biodiversity conservation. Extensive dairy sheep grazing also contributes to rural development by generating employment and income in marginal, low-productivity lands that can support few economic alternatives. In particular, we found that sheep farmers who produce high-value products, such as cheese, have enhanced their economic profitability and are less dependent on public subsidies. However, careful attention to sustainable practices, support for new generations of farmers, and streamlined supply chains are required. These would contribute to ensure socio-economic benefits for farmers, avoid the ecological costs associated with grazing abandonment, and enhance ecosystem services for the whole society.
... Today, "livestock" and humans comprise 96 percent of the aggregate weight of land mammals on the planet ( Bar-On et al., 2018). Agriculture is a salient and sometimes leading cause of many major problems: global warming; species extinctions; killing of big herbivores and carnivores; massive insect species and population declines; devastation of freshwater species; nitrogen, pesticide, and greenhouse pollution; homogenization of domestic plants and animals; and emergence of devastating zoonotic and other infectious diseases Hayek et al., 2021). We tend to think of "habitat destruction" and "invasive species" as distinct and equal contributors to biodiversity collapse. ...
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Invasion biology is increasingly facing criticism for its moral attitude towards and treatment of “invasive alien species.” In this paper, we argue that invasion biology relies upon dubious assumptions of human supremacy. We also argue that the language and official classification of introduced animals is intertwined with their ethically problematic treatment. Our focus is on several factors that help to shape the meaning of terms such as “invasive,” “alien,” “pest” and “feral.” These factors are the differential treatment of “invasives” versus humans and other ecologically damaging animals (especially animals in agriculture); and the stock or normalized treatment and the performative treatment of animals who are demonized as invasive aliens. The resulting language and classifications in turn tend to promote the wrongful treatment of these animals. We propose that such language should be essentially removed from biological and conservation sciences. Indeed, invasion biologists should come together to find a new name for their discipline—or rather, for the discipline “invasion biology” might become when it jettisons its problematic allegiance to human supremacy and embraces a more progressive moral attitude towards nonhuman sentient beings.
... Established evidence suggests that well-planned plant-based diets can help lower the risk of Non-Communicable Diseases (NCDs) such as cancer, obesity and cardiovascular diseases (Satija and Hu, 2018;Willet et al., 2019). Plant-based food products also tend to have a lower environmental impact in terms of greenhouse-gas emissions, eutrophication and acidification potentials, and land, freshwater and fossil fuel use, when compared to animal-sourced foods (Chai et al., 2019;Hayek et al., 2021;Poore and Nemecek, 2018;Willet et al., 2019). However, despite these potential benefits, large-scale transitions toward healthier and more sustainable diets will not happen automatically. ...
PURPOSE: Recent reviews and reports have highlighted the need for integrated, context-specific efforts to enable sustainable food transitions. This study aimed to identify pathways to promote healthier and more environmentally friendly food practices in school contexts, with a focus on increased plant-based eating. DESIGN/METHODOLOGY/APPROACH: The study used a systemic approach with data collected from relevant stakeholders in an EU country (Portugal) at diverse levels of influence in the school meals system (i.e. proximal, intermediate, distal; from end-consumers to food providers, market actors, civil society organizations, and policy and decision-makers). Data from individual interviews (N=33) were subjected to thematic analysis. FINDINGS: Meat-centric cultural perceptions of a ‘proper meal’ can be a socio-emotional barrier for sustainable food transitions in schools. Main pathways identified to unlock these transitions included: (1) Levering orientations toward ethical and environmentally beneficial consumption; (2) Improving and increasing the offer of plant-based meals; and (3) Mobilizing local communities and society. ORIGINALITY/VALUE: The current findings suggest that promoting healthier and more environmentally friendly food practices in schools requires systemic, integrated approaches which focus on food consumption, food provision, and the broader political and sociocultural environment.
... The food production value of grazing land has been questioned [23,24]. In addition, the Climate Change Committee has recommended that up to 32% of the UK's grassland area should be removed from ruminant production by 2035 [25]. ...
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Grassland accounts for a high proportion of the agricultural area of the United Kingdom, but the significance of its contribution to the nation’s food supply has been questioned. Using representative figures for the composition of UK ruminant livestock diets, we estimated the total production of human-edible protein from grass and forage crops consumed by cattle and sheep. We found that this equates to 21.5 g of protein per person per day, of which 15.2 g comes from milk, 4.71 g from beef and 1.60 g from sheep meat. This represents 45% of the total amount of human-edible animal protein produced in the UK (46.6 g/head) and is equivalent to one-third of the recommended adult human daily protein intake of 64 g/head. Given the growing pressure to produce food in a more resource-efficient manner, grasslands have a valuable role to play in providing food alongside multiple public goods.
Sustainability of livestock production is a highly contested issue in agricultural sustainability discourse. This study aimed to assess the environmental impact of farms using semi-natural grasslands in Finland, or so-called High Nature Value (HNV) farms. We estimated the environmental impact of 11 such farms, including greenhouse gas emissions (GHG), nitrogen (N) balance, land occupation, and carbon storage. We also accounted for unique biodiversity, defined in this study as communities that are dependent on semi-natural grasslands. We compared these to the alternative states of the farms, specifically a hypothetical farm with the same production output but without access to semi-natural grasslands. GHG emissions at the farm level (tCO2eq/ha) in HNV farms were 64% lower than on the alternative farms; GHG emissions at the product level (tCO2eq/t LW) and N balance (N kg/ha) were 31% and 235% lower, respectively. The carbon stocks were 163% higher at farm level. Biodiversity values, indicated by the share of semi-natural grassland in management, ranged from 23% to 83% on HNV farms. Six out of eleven farms would need to increase their arable land occupation by an average of 39% of arable land to fulfil their needs for animal feed if they did not utilize semi-natural grassland. This study contributes to growing evidence that HNV farming systems can support sustainable production by minimising arable land occupation, reducing nutrient loses, and increasing carbon storage while maintaining unique biodiversity.
Food systems, including supply chains, account for approximately one-third of global anthropogenic GHGs emissions. We construct a bottom-up GHG inventory of China’s food system from farm to fork for the period 1990–2018. The decomposition method is used to assess regional differentiated drivers. GHG emissions reduced by 6.8% between 1990 and 2000 due to energy structure changes in East, Central and Southwest China. They then increased by 2.3% (2001–2010) because of rapid economic growth. Further large increases of 13.1% (2011–2018) were driven by growing consumption expenditure and GHG-intensive food consumption. In 2018 total emissions from China’s food system, including supply chains, was 1.55 Gt CO2e yr-1 (95%CI 1.07-2.03 Gt CO2e yr−1). Scenario simulation shows that demand- and supply-side synergies can offset emissions increases from high-quality protein food demands. Results demonstrate the importance of supply-side production spatial optimization and green source food importation for mitigating GHGs emissions.
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A Total Liberation Pathway is proposed, involving an abolition of compulsory work for all beings. This trajectory involves drastically shortening humans' workweek, ending the exploitation of animals including for food, and rewilding ecosystems currently exploited as "working landscapes." Using the climate models the Global Calculator and C-Roads Pro, I demonstrate that the Total Liberation Pathway could return atmospheric CO2 and global temperature levels to the 300 ppm and 1°C targets demanded by the 2010 People's Agreement of Cochabamba, and could achieve the precautionary target of rewilding of 75% of the Earth. I also propose possible contours of a strategy of resistance and reconstruction. Although Indigenous communities and energy and agricultural workers will have an indispensable role in the transition, through control over land, and key economic bottlenecks, the entire resistance of human and nonhuman beings offers hope. Letting nature play, humans included, could enable a livable future.
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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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Food's environmental impacts are created by millions of diverse producers. To identify solutions that are effective under this heterogeneity, we consolidated data covering five environmental indicators; 38,700 farms; and 1600 processors, packaging types, and retailers. Impact can vary 50-fold among producers of the same product, creating substantial mitigation opportunities. However, mitigation is complicated by trade-offs, multiple ways for producers to achieve low impacts, and interactions throughout the supply chain. Producers have limits on how far they can reduce impacts. Most strikingly, impacts of the lowest-impact animal products typically exceed those of vegetable substitutes, providing new evidence for the importance of dietary change. Cumulatively, our findings support an approach where producers monitor their own impacts, flexibly meet environmental targets by choosing from multiple practices, and communicate their impacts to consumers.
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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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Food loss is widely recognized as undermining food security and environmental sustainability. However, consumption of resource-intensive food items instead of more efficient, equally nutritious alternatives can also be considered as an effective food loss. Here we define and quantify these opportunity food losses as the food loss associated with consuming resource-intensive animal-based items instead of plant-based alternatives which are nutritionally comparable, e.g., in terms of protein content. We consider replacements that minimize cropland use for each of the main US animal-based food categories. We find that although the characteristic conventional retail-to-consumer food losses are ≈30% for plant and animal products, the opportunity food losses of beef, pork, dairy, poultry, and eggs are 96%, 90%, 75%, 50%, and 40%, respectively. This arises because plant-based replacement diets can produce 20-fold and twofold more nutritionally similar food per cropland than beef and eggs, the most and least resource-intensive animal categories, respectively. Although conventional and opportunity food losses are both targets for improvement, the high opportunity food losses highlight the large potential savings beyond conventionally defined food losses. Concurrently replacing all animal-based items in the US diet with plant-based alternatives will add enough food to feed, in full, 350 million additional people, well above the expected benefits of eliminating all supply chain food waste. These results highlight the importance of dietary shifts to improving food availability and security.
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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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Better stewardship of land is needed to achieve the Paris Climate Agreement goal of holding warming to below 2 °C; however, confusion persists about the specific set of land stewardship options available and their mitigation potential. To address this, we identify and quantify "natural climate solutions" (NCS): 20 conservation, restoration , and improved land management actions that increase carbon storage and/or avoid greenhouse gas emissions across global forests, wetlands, grasslands, and agricultural lands. We find that the maximum potential of NCS-when constrained by food security, fiber security, and biodiversity conservation-is 23.8 petagrams of CO 2 equivalent (PgCO 2 e) y −1 (95% CI 20.3-37.4). This is ≥30% higher than prior estimates, which did not include the full range of options and safeguards considered here. About half of this maximum (11.3 PgCO 2 e y −1) represents cost-effective climate mitigation, assuming the social cost of CO 2 pollution is ≥100 USD MgCO 2 e −1 by 2030. Natural climate solutions can provide 37% of cost-effective CO 2 mit-igation needed through 2030 for a >66% chance of holding warming to below 2 °C. One-third of this cost-effective NCS mitigation can be delivered at or below 10 USD MgCO 2 −1. Most NCS actions-if effectively implemented-also offer water filtration, flood buffer-ing, soil health, biodiversity habitat, and enhanced climate resilience. Work remains to better constrain uncertainty of NCS mitigation estimates. Nevertheless, existing knowledge reported here provides a robust basis for immediate global action to improve ecosystem stewardship as a major solution to climate change. climate mitigation | forests | agriculture | wetlands | ecosystems
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. © 2018 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license