Climate Change

Making sense of different numbers

Regarding livestock’s contribution to GHG emissions, a range of different numbers feature in public debates: 18% (FAO, 2006) [21], 14.5% (FAO, 2013) [22], 11.1 (FAO, 2023) [23], 15% (Poore & Nemecek, 2018) [14], 16.5% (Twine, 2021) [25], 20% (Xu et al., 2021) [2]

• Robust calculations account for emissions across the whole supply chain: including land-use change for crop, livestock and feed production, fertilizers and pesticides, enteric fermentation and manure management.
• Carbon opportunity costs – the amount of carbon that could be sequestered by reforesting agricultural areas – can also be calculated to demonstrate the full potential of emissions savings.

Sources

[1] Crippa, M., E. Solazzo, D. Guizzardi, et al. (2021): Food systems are responsible for a third of global anthropogenic GHG emissions. Nature Food 2(3), 198–209. 
[2] Xu, X., P. Sharma, et al. (2021): Global greenhouse gas emissions from animal-based foods are twice those of plant-based foods. Nature Food 2(9), 724–732. 
[3] Babiker, M., G. Berndes, K. Blok et al. (2022): Cross-sectoral perspectives. In IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA.
[4] The Breakthrough Institute (2023): Livestock Don’t Contribute 14.5% of Global Greenhouse Gas Emissions. Available at: https://thebreakthrough.org/issues/food-agriculture-environment/livestock-dont-contribute-14-5-of-global-greenhouse-gas-emissions [Accessed: 30.10.2023] 
[5] Forster, P., T. Storelvmo, K. Armour, et al. (2021): The Earth’s Energy Budget, Climate Feedbacks, and Climate Sensitivity. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 923–1054
[6] Climate & Clean Air Coalition (2021): Benefits and costs of mitigating methane emissions. Available at: https://www.ccacoalition.org/content/benefits-and-costs-mitigating-methane-emissions [Accessed 10.04.2024] 
[7] Climate & Clean Air Coalition (2017): One million premature deaths linked to ozone air pollution. Available at: https://www.ccacoalition.org/news/one-million-premature-deaths-linked-ozone-air-pollution [Accessed: 10.04.2024] 
[8] United Nations Environment Programme & Climate and Clean Air Coalition (2021): Global Methane Assessment: Benefits and Costs of Mitigating Methane Emissions. United Nations Environment Programme, Nairobi
[9] Nature (2021): Control methane to slow global warming — fast. Nature 596(7873), 461–461.
[10] Clark, M. A., N. G. G. Domingo, et al. (2020): Global food system emissions could preclude achieving the 1.5° and 2°C climate change targets. Science 370(6517), 705–708.
[11] IPCC (2019): Climate Change and Land. An IPCC Special Report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems. IPCC.
[12] Sun, Z., L. Scherer, et al. (2022): Dietary change in high-income nations alone can lead to substantial double climate dividend. Nature Food 3(1), 29–37.
[13] Eisen, M. B. & P. O. Brown (2022): Rapid global phaseout of animal agriculture has the potential to stabilize greenhouse gas levels for 30 years and offset 68 percent of CO2 emissions this century. PLOS Climate 1(2), e0000010.
[14] Poore, J. & T. Nemecek (2018): Reducing food’s environmental impacts through producers and consumers. Science 360(6392), 987–992
[15] Poore, J. & T. Nemecek (2019): Erratum for the Research Article “Reducing food’s environmental impacts through producers and consumers”. Science 363(6429), eaaw9908. doi:10.1126/science.aaw9908
[16] Hayek, M. N., H. Harwatt, W. J. Ripple, et al. (2021): The carbon opportunity cost of animal-sourced food production on land. Nature Sustainability 4(1), 21–24. doi:10.1038/s41893-020-00603-4
[17] Ritchie, H. (2021): What are the carbon opportunity costs of our food? Our World in Data. Available at: https://ourworldindata.org/carbon-opportunity-costs-food [Accessed: 30.10.2023]
[18] Kustar, A. & D. Patino-Echeverri (2021): A Review of Environmental Life Cycle Assessments of Diets: Plant-Based Solutions Are Truly Sustainable, even in the Form of Fast Foods. Sustainability 13(17), 9926.
[19] Hallström, E., A. Carlsson-Kanyama, et al. (2015): Environmental impact of dietary change: a systematic review. Journal of Cleaner Production 91 1–11.
[20] Clark, M., M. Springmann, M. Rayner, et al. (2022): Estimating the environmental impacts of 57,000 food products. Proceedings of the National Academy of Sciences 119(33), e2120584119. doi:10.1073/pnas.2120584119
[21] FAO (2006): Livestock’s long shadow – environmental issues and options. Food and Agriculture Organization of the United Nations (FAO), Rome.
[22] Gerber, P.J., H. Steinfeld, B. Henderson, et al. (2013): Tackling climate change through livestock – A global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations (FAO), Rome
[23] FAO (2022): GLEAM 3 Dashboard. In: Shiny Apps. Available at https://foodandagricultureorganization.shinyapps.io/GLEAMV3_Public/ [Accessed: 30.10.2023]
[25] Twine, R. (2021): Emissions from Animal Agriculture—16.5% Is the New Minimum Figure. Sustainability 13(11), 6276. doi:10.3390/su13116276
[26] Ritchie, H. (2021): Emissions from food alone could use up all of our budget for 1.5°C or 2°C – but we have a range of opportunities to avoid this. Our World in Data. Available at: https://ourworldindata.org/food-emissions-carbon-budget [Accessed: 16.11.2023]

* Based on Xu et al. (2021); Country emissions from Climate watch for 2010 – GWP of 25 for methane adapted to 34 to match data by Xu et al. (2021) and make comparable