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

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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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Brief CommuniCation
https://doi.org/10.1038/s41893-020-00603-4
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.
e-mail: matthew.hayek@nyu.edu
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
NATURE SUSTAINABILITY | VOL 4 | JANUARY 2021 | 21–24 | www.nature.com/natsustain 21
Content courtesy of Springer Nature, terms of use apply. Rights reserved
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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
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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. © 2018 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license