Global greenhouse gas emissions from animal-based foods are twice those of plant-based foods

Abstract

Agriculture and land use are major sources of greenhouse gas (GHG) emissions but previous estimates were either highly aggregate or provided spatial details for subsectors obtained via different methodologies. Using a model–data integration approach that ensures full consistency between subsectors, we provide spatially explicit estimates of production- and consumption-based GHG emissions worldwide from plant- and animal-based human food in circa 2010. Global GHG emissions from the production of food were found to be 17,318 ± 1,675 TgCO2eq yr−1, of which 57% corresponds to the production of animal-based food (including livestock feed), 29% to plant-based foods and 14% to other utilizations. Farmland management and land-use change represented major shares of total emissions (38% and 29%, respectively), whereas rice and beef were the largest contributing plant- and animal-based commodities (12% and 25%, respectively), and South and Southeast Asia and South America were the largest emitters of production-based GHGs. The quantification of greenhouse gas emissions related to food production and consumption is still largely hindered by the availability of spatial data consistent across sectors. This study provides a detailed account of emissions from land-use change, farmland, livestock and activities beyond the farm gate associated with plant- and animal-based foods/diets—culminating in local-, country- and global-level emissions from each major agricultural commodity.

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Articles
https://doi.org/10.1038/s43016-021-00358-x
1University of Illinois, Urbana, IL, USA. 2Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, France. 3Statistics
Division, FAO, Rome, Italy. 4Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Aberdeen, UK.
5PlantPure Communities, Inc., Mebane, NC, USA. ✉e-mail: jain1@illinois.edu
The global population has quadrupled over the last century.
Demographic growth and associated economic growth have
increased global food demand and caused dietary changes,
such as eating more animal-based products. The United Nations
projects that food production from plants and animals will need to
increase 70% by 2050, compared to 2009, to meet increasing food
demand1. This will drive the expansion of food subsectors, includ-
ing crop cultivation and livestock production, as well as product
transportation and processing, materials (fertilizer and pesticides)
and irrigation2. Increased food production may accelerate land-use
changes (LUCs) for agriculture, resulting in greater greenhouse gas
(GHG) emissions, reduced carbon sequestration and further cli-
mate change. Developing climate mitigation strategies will require
estimates of all major GHG emissions (for example, CO2, CH4 and
N2O) from the production and consumption of total and individ-
ual plant- and animal-based food from all food-related subsectors,
such as land-use change and farmland activities, at local, regional
and global scales—which is the overall objective of this study. Such
comprehensive and quantitative estimates require a framework
that dynamically represents the environmental, management and
human drivers of major GHGs while satisfying carbon and nitrogen
mass-conservation among plant and livestock production and con-
sumption systems.
Previous efforts have been made to assess GHG emissions from
agriculture, forestry and other land use (AFOLU)3,4, a critical subset
of food systems emissions5–7. The recent Intergovernmental Panel
on Climate Change (IPCC) Special Report on Climate Change and
Land (SRCCL)6 and subsequent work7 quantified emissions within
and beyond the farm gate, the latter referring to emissions caused
by food systems that are not covered by AFOLU sectors, such as fer-
tilizer manufacturing, product processing and transportation (Fig.
1), to be in the range of 10,800–19,100 TgCO2eq yr−1 for the decade
2008–2017. These estimates combined results from diverse stud-
ies on farm-gate agriculture and associated land use4 with global
estimates of emissions along the supply chain up to retail and con-
sumption, each study using a different methodology. The annual
assessment of the global carbon budget provides C O2-only emissions
from LUC8. In contrast, the Food and Agriculture Organization
(FAO) gives CO2 emissions from forest LUC and peatland degra-
dation9, but those studies do not cover emissions from changes in
agricultural management intensity8. Moreover, CH4 and N2O emis-
sions from agricultural activities are provided globally by different
datasets10,11, usually based on estimation approaches defined by the
IPCC Guidelines12. The IPCC AR5 WG33 and FAOSTAT4 quanti-
fied regional GHG emissions from subsectors of agriculture and
land use. There are also studies focusing on spatially explicit GHG
emissions for selected crops13, emissions of the life cycle of agri-
cultural production5, such as the FAO GLEAM model to estimate
global livestock emissions for 200514, and accounting for carbon
opportunity costs of agricultural land15.
This study quantifies CO2, CH4 and N2O emissions from the
production and consumption of all plant- and animal-based foods
on a grid scale using a consistent unified model–data integration
framework. Our approach builds upon and extends the data and
methods published in the literature by implementing them into the
Integrated Science Assessment Model (ISAM)16.
Our approach advances the field for three main reasons. First,
we have a dynamic representation of environmental drivers, such
as climate, CO2 and of direct human drivers (LUC) using a consis-
tent set of mass-conserving equations and parameters for biophysi-
cal and biogeochemical processes to estimate the plant carbon and
nitrogen dynamics. In comparison, inventory-based methods, such
as those used by the IPCC12, usually consider environmental fac-
tors as static functions12. Second, we estimate CO2 emissions and
Global greenhouse gas emissions from
animal-based foods are twice those of
plant-based foods
Xiaoming Xu 1, Prateek Sharma1, Shijie Shu 1, Tzu-Shun Lin1, Philippe Ciais 2,
Francesco N. Tubiello 3, Pete Smith 4, Nelson Campbell5 and Atul K. Jain 1 ✉
Agriculture and land use are major sources of greenhouse gas (GHG) emissions but previous estimates were either highly
aggregate or provided spatial details for subsectors obtained via different methodologies. Using a model–data integra-
tion approach that ensures full consistency between subsectors, we provide spatially explicit estimates of production- and
consumption-based GHG emissions worldwide from plant- and animal-based human food in circa 2010. Global GHG emis-
sions from the production of food were found to be 17,318 ± 1,675 TgCO2eq yr−1, of which 57% corresponds to the production of
animal-based food (including livestock feed), 29% to plant-based foods and 14% to other utilizations. Farmland management
and land-use change represented major shares of total emissions (38% and 29%, respectively), whereas rice and beef were
the largest contributing plant- and animal-based commodities (12% and 25%, respectively), and South and Southeast Asia and
South America were the largest emitters of production-based GHGs.
NATURE FOOD | VOL 2 | SEPTEMBER 2021 | 724–732 | www.nature.com/natfood
724
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