Well I have never been in a subject where the figures show such a wide range. I think we get from 12% to 51% of total global emissions with everything in between. It started in 2006 with Livestock’s Long Shadow, a study that brought an alarming result for the beef and dairy sector and caused them to demand a partnership with FAO from then on.
So first of all notice the heading – the contribution of livestock emissions , which is a subsector of agriculture emissions.
- The lowest is that agriculture is the second-largest contributor to global greenhouse gas emissions after the energy sector (including transport), producing 12.56% of all emissions. And livestock will be a large percentage of this. https://www.climatewatchdata.org/sectors/agriculture. This excludes land use change and forestry.
- The second to lowest is the 2013 FAO assessment, coming in at 14.5%. This is re-working the 2006 report using different data sets.
- The third lowest is 2006 FAO assessment Livestock’s Long Shadow, which came in at 18%.
- The IPCC AR5 came in with 24% for agriculture, forestry and other land use. And that is how they define a whole sector these days. It’s the AFOLU sector.
- Vermeulen et al came up with a figure of 19-29% of emissions for food systems. This has been widely cited including by the major EAT-Lancet study of Planetary Diets. (Climate Change and Food Systems. Ann Rev Environ Resour 2012 27 195-222.)
- The highest estimate of all is by Robert Goodland and Jeff Anhang for the Worldwatch Institute in 2009. It came up with 51% of emissions being from livestock alone. https://awellfedworld.org/livestock-climate-advanced/vermhttps://awellfedworld.org/livestock-climate-advanced/https://awellfedworld.org/livestock-climate-advanced/
How on earth do we make sense of all this? I asked Professor James Renwick who replied to me on 2 Nov 2019.
I think the Lancet study is the best right now, and probably closest to what you want.” (They cited Vermeulen et all at 19-28%)
Others have grappled to find the right figure. From the author of We are the Weather – Saving the Planet begins at Breakfast, Jonathan Safron Foer – his appendix and it covers the difference between 18% and 51%, after correspondence with Jeff Anhang (his co-author Robert Goodland who hd impressive credentials as an environmental assessor, died in 2014). Jeff Anhang works for the International Finance Corporation a member of the World Bank group.
Foer’s appendix, entitled 14.5%/51%, answers the FAO rebuttal of Goodland and Anhang’s Worldwatch Institute 2009 paper, and cites subsequent correspondence which confirms theirs was peer reviewed and the FAO authors didn’t answer the question whether theirs was peer reviewed. Although the discussion around the wrong Global Warming Potential timeframe for methane is something I don’t care to comment on because I don’t fully understand it, Goodland and Anhang argue cogently in favour of including carbon dioxide exhaled from livestock. FAO doesn’t include this, nor do other studies and it remains contentious.
Goodland and Anhang say “Strangely, (the FAO) does not count the much larger amount of annual GHG reduction from photosynthesis that are for gone by using 26% of land worldwide for grazing livestock and 33% of arable land for growing food, rather than allowing it to regenerate forest. By itself, leaving a significant amount of tropical land used for grazing livestock and growing feed to regenerate as forest could potentially mitigate as much as half or even more of all anthropogenic greenhouse gases.”
Foer concludes that neither figure is accurate, but he finds the higher the more persuasive. And when Foer asked Anhang what we need to do to meet the goals of the Paris Accord he answered,
“It seems to me impossible to reverse climate change by keeping possible fuels. That’s because the amount of renewable energy infrastructure needed to stop climate change has been estimated by the international energy agency to cost list $53 trillion and take at least 20 years, by which time it’s predicted to be too late to reverse climate change. In contrast replacing animal products with alternatives offers a unique dual opportunity to reduce greenhouse gas emissions quickly well freeing up land to enable more trees to capture excess atmospheric carbon in the near term. So replacing animal products with alternatives seems to be the only pragmatic way to reverse climate change before it’s too late.”