Global greenhouse gas emissions from animal-based foods ...

1 DispatchDate: ProofNo: 358, Articles 1. 2. 3. Global greenhouse gas emissions from animal-based foods are twice those of 4. 5. 6. 7. 8 plant-based foods 9. 10. 11 Xiaoming Xu 1, Prateek Sharma1, Shijie Shu 1, Tzu-Shun Lin1, Philippe Ciais 2, 12 Francesco N. Tubiello 3, Pete Smith 4, Nelson Campbell5 and Atul K. Jain 1 . 13. 14. 15 Agriculture and land use are major sources of greenhouse gas (GHG) emissions but previous estimates were either highly 16 aggregate or provided spatial details for subsectors obtained via different methodologies. Using a model data integra- 17 tion approach that ensures full consistency between subsectors, we provide spatially explicit estimates of production- and 18 consumption-based GHG emissions worldwide from plant- and animal-based human food in circa 2010.

2 Global GHG emis- 19 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 20 animal-based food (including livestock feed), 29% to plant-based foods and 14% to other utilizations. Farmland management 21 and land-use change represented major shares of total emissions (38% and 29%, respectively), whereas rice and beef were 22 the largest contributing plant- and animal-based commodities (12% and 25%, respectively), and South and Southeast Asia and 23 South America were the largest emitters of production-based GHGs. 24. T. 25. 26 he Global population has quadrupled over the last century. 2008 2017. These estimates combined results from diverse stud- 27 Demographic growth and associated economic growth have ies on farm-gate agriculture and associated land use4 with Global 28 increased Global food demand and caused dietary changes, estimates of emissions along the supply chain up to retail and con- 29 such as eating more animal-based products.

3 The United Nations sumption, each study using a different methodology. The annual 30 projects that food production from plants and animals will need to assessment of the Global carbon budget provides CO2-only emissions 31 increase 70% by 2050, compared to 2009, to meet increasing food from LUC8. In contrast, the Food and Agriculture Organization 32 demand1. This will drive the expansion of food subsectors, includ- (FAO) gives CO2 emissions from forest LUC and peatland degra- 33 ing crop cultivation and livestock production, as well as product dation9, but those studies do not cover emissions from changes in 34 transportation and processing, materials (fertilizer and pesticides) agricultural management intensity8.

4 Moreover, CH4 and N2O emis- 35 and irrigation2. Increased food production may accelerate land-use sions from agricultural activities are provided globally by different 36 changes (LUCs) for agriculture, resulting in greater greenhouse gas datasets10,11, usually based on estimation approaches defined by the 37 (GHG) emissions , reduced carbon sequestration and further cli- IPCC Guidelines12. The IPCC AR5 WG33 and FAOSTAT4 quanti- 38 mate change. Developing climate mitigation strategies will require fied regional GHG emissions from subsectors of agriculture and 39 estimates of all major GHG emissions (for example, CO2, CH4 and land use. There are also studies focusing on spatially explicit GHG. 40 N2O) from the production and consumption of total and individ- emissions for selected crops13, emissions of the life cycle of agri- 41 ual plant- and animal-based food from all food-related subsectors, cultural production5, such as the FAO GLEAM model to estimate 42 such as land-use change and farmland activities, at local, regional Global livestock emissions for 200514, and accounting for carbon 43 and Global scales which is the overall objective of this study.

5 Such opportunity costs of agricultural land15. 44 comprehensive and quantitative estimates require a framework This study quantifies CO2, CH4 and N2O emissions from the 45 that dynamically represents the environmental, management and production and consumption of all plant- and animal-based foods Q1. 46 human drivers of major GHGs while satisfying carbon and nitrogen on a grid scale using a consistent unified model data integration 47. Q2 Q3 Q4 Q5. mass-conservation among plant and livestock production and con- framework. Our approach builds upon and extends the data and 48 sumption systems. methods published in the literature by implementing them into the .. 49 Previous efforts have been made to assess GHG emissions from Integrated Science Assessment Model (ISAM)16.

6 50 agriculture, forestry and other land use (AFOLU)3,4, a critical subset Our approach advances the field for three main reasons. First, 51 of food systems emissions5 7. The recent Intergovernmental Panel we have a dynamic representation of environmental drivers, such as 52 on Climate Change (IPCC) Special Report on Climate Change and climate, CO2 and of direct human drivers (LUC) using a consistent 53 Land (SRCCL)6 and subsequent work7 quantified emissions within set of mass-conservative equations and parameters for biophysi- . Q6.. 54 and beyond the farm gate, the latter referring to emissions caused by cal and biogeochemical processes to estimate the plant carbon and 55 food systems that are not covered by AFOLU sectors, such as fertil- nitrogen dynamics.

7 In comparison, inventory-based methods, such 56 izer manufacturing, product processing and transportation (Fig. 1), as those used by the IPCC12, usually consider environmental fac- 57 to be in the range of 10,800 19,100 TgCO2eq yr 1 for the decade tors as static functions12. Second, we estimate CO2 emissions and 58. 59. 60 1. University of Illinois, Urbana, IL, USA. 2 Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, France. 3 Statistics 61 Division, FAO, Rome, Italy. 4 Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Aberdeen, UK. 62 5. PlantPure Communities, Inc., Mebane, NC, USA. e-mail: 63 A B. Nature Food | DispatchDate: ProofNo: 358, Articles Nature Food 64 Beyond farm gate Land-use change 65 Mining, manufacturing and Land-use change transporting fertilizers and Product processing 66 pesticides emissions 1,296.

8 67 666. 5,094. 68. 69. 70. 71 Plant-based food animal-based food Other utilizations 72 Consumption-based Consumption-based Consumption-based 4,963 9,923 2,133. 73 19% CO2, 6% CH4, 4% N2O 32% CO2, 20% CH4, 6% N2O 10% CO2, 2% CH4, 1% N2O. 74. 75. 76. 77. 78 Sum of Enteric Manure transportation, 79 Cropland Pastureland fermentation management trade and 80 4,009 2,316. 3,160 448 stock variation 81 139. 82 Fuel and energy 83 use 169. Farmland Livestock 84. 85. 86 Fig. 1 | GHG emissions from different subsectors of plant- and animal-based food production/consumption. The contributions of individual GHGs 87 provided are the percentage of the total emissions . Solid arrows indicate production-based emissions , and solid and dashed arrows combined are 88 consumption-based emissions .

9 The values in the boxes are mean values for 2007 2013, which may slightly differ from the median values of 10,000 Monte 89 Carlo simulations in the text. Values are expressed in TgCO2eq. 90. 91. 92 sinks from changes in agricultural land management intensity from countries, where consumption-based emissions are calculated by 93 a set of diverse and spatially variable practices such as ploughing combining emissions from transportation, stock variation, import 94 the soil, planting crops, fertilization, irrigation, harvesting grains and export with the estimates of production-based emissions . 95 and recovering crop residues. In comparison, most Global vegeta- 96 tion models have a very simple or no representation of those prac- Results 97 tices, and bookkeeping models used for land-use emissions ignore agricultural land and biomass.

10 The estimated agricultural bio- 98 changes in management intensity3. Third, we separate emissions mass production for 171 crops listed in Supplementary Table 1 and 99 from feed production in cropland and grazing land so that they grazing land (see Supplementary Methods for definitions) for 100 can be attributed to livestock production, based on the commodity human food and animal feed, LUC areas associated with this pro- 101 balance between production and consumption, which allows us to duction, and other non-food utilization such as fibre, rubber and 102 attribute the total food-related GHG emissions specifically to plant- cotton, but not energy crops, are linked consistently to the ISAM. 103 and animal-based human food.