Wednesday, July 17, 2024

Climate Change and Animal Agriculture – Part 1

"If we save the living environment, the biodiversity that we have left today, then we will also automatically save the physical environment. If we only save the physical environment, then we will ultimately lose both." — E. O. Wilson.

Vegan Sustainability Magazine, Feb 2018, Creative Commons Licence 

Why transition to a vegan food system?  At Vegan Sustainability we believe we should go vegan because we love animals and we don’t wish to harm any of them.  It is obvious that animals are sentient feeling beings and they have an intrinsic right to live free from oppression and violence. Animals are not objects, they are the conscious choice-making subjects of their own lives just as we are of our lives.  Animal agriculture and the fishing industry are inherently violent and unethical industries that hurt and harm trillions of sentient living beings. Choosing a vegan lifestyle is choosing to not participate in this violent system. Every time a single person chooses to go vegan then lives are saved and animals are freed from the shocking conditions of imprisonment found on even “well managed” farms. 

The animal centred food system has many other harmful environmental side effects. Globally it is the primary cause of biodiversity loss through habitat degradation, fishing, hunting and trading in animals.  It also causes antibiotic resistance, zoonotic diseases, air and water pollution and soil erosion (Rockström et al., 2009b; Godfray et al., 2010; Amundson et al., 2015). “It is also a primary force behind the transgression of the Planetary Boundaries for nitrogen, phosphorus, climate change, biosphere integrity, land-system change and freshwater use (Rockström et al., 2009b).  “A very large proportion of agricultural land, almost 80 per cent, is allocated to livestock for the production of meat, dairy and other animal proteins. Yet these land-based animal products provide only about 17% of calories and 33% of protein consumed by humans globally (FAO, 2015).” A transition to a plant based agriculture system would free up enough food for an additional four to six billion people.  

In this report we focus on how Animal Agriculture drives climate change.  We explain why renewable energy systems do not sequester any greenhouse gases from the atmosphere and why using biomass and biofuels, even as a transition strategy, will strongly increase climate change emissions.  Finally we show that by simply transitioning to a vegan diet and reforesting those areas deforested for animal agriculture we can completely reverse climate change.  Many of the authors of these research papers may not advocate a vegan agricultural system but the data they present highlights the incredible benefits of such a transition.  We know that time has already run out for thousands of species, who have already gone extinct.  Tragically more extinctions are inevitable.  The question now is how quickly can we make this social and cultural transition in order to minimise further species loss.  The FAO is predicting a 70% increase in animal agriculture by 2035 but instead we need to transition to a vegan food system.   We hope that you will join us in making this important life affirming choice.  But we ask that you also join this social and cultural vegan movement as it advocates for change at the local and national level.  Let us work towards a vegan world.  By working together we can make it happen.  To watch a ten minute video on how this transition can reverse climate change, biodiversity loss and desertification please watch this video by Sailesh Rao of

Report Summary 

The 2014 IPCC AR5 estimated the 2010 GHG emissions at 49 Gt CO2eq/yr.  According to the IPCC globally AFOLU – Agriculture, Forestry and Other Land Use Change – is responsible for 24% of GHG emissions. “Annual GHG emissions from agricultural production were estimated at 5.0 – 5.8 GtCO2eq / yr – growing by about 1 % / yr.”  The “annual GHG flux from land use and land-use change activities accounted for approximately 4.3 – 5.5 GtCO2eq/yr.” Estimates for the contribution of animal agriculture vary significantly.  We have produced our own estimate of these emissions summarised below.  

  • The IPCC shows that agriculture is responsible for 5.5 GtCO2eq/yr and animal agriculture is responsible for 3.8 GtCO2eq/yr. 
  • The IPCC shows that FOLU generates 15.3 GtCO2eq/yr emissions from of deforestation and degradation and 10.3 GtCO2eq/yr of sequestration from reforestation and regrowth.  We assigned 13 GtCO2eq/yr to agriculture.  Assuming animal agriculture is responsible for 80%, this increases its share by an additional 10.4 GtCO2eq/yr. 
  • The food system uses 30% of Fossil Fuels and generates 20% of GHG emissions. 20% of 49 Gt CO2eq/yr gives 9.8 Gt CO2eq/yr. Assuming that animal agriculture uses 70% of fossil fuels increases its share by 6.9 Gt CO2eq/yr. 
  • Food Waste is responsible for 4.4 GtCO2eq/yr or 9% of all GHG emissions – about a third of that is for animal agriculture (1.5 GtCO2eq/yr). 
  • The Global Land Outlook Report estimates that 2Gt of Carbon are lost annually from agricultural soil degradation which is 7.3 Gt CO2 e/yr. As 80% of Agricultural Land is used for animal agriculture it generates an additional 5.9 Gt CO2 e/yr. 
  • 8,650 million tons of animal feed is converted to 460 million tons of meat and 8,190 million tons is excreted as waste in the animals’ breath and excreta.  Assuming 40% of this is carbon is 3,276 Mt of C or 12 Gt of CO2. 3.5 GtCO2eq/yr is accounted for leaving 8.5 GtCO2eq/yr unaccounted for.  (Anhang and Goodland estimated 8.8 Gt in 2009.) This adds an additional 8.5 GtCO2eq/yr to animal agriculture emissions.   

Total food system GHG emissions 48.9 GtCO2eq/yr or 63% of overall emissions. 

Total animal agriculture GHG emissions 37.4 GtCO2eq or 48% of overall emissions. 

Other FOLU emissions totalled 2.3 GtCO2eq/yr and 10.3 GtCO2eq/yr of sequestration.   

Fossil fuel emissions totalled 36.8 GtCO2eq/yr. 9.8 GtCO2eq/yr was for the food system. 

So non-food system related fossil fuels generate a further 27 GtCO2eq/yr.  

Emissions would total 78.2 GtCO2eq/yr and 10.3 GtCO2eq/yr of sequestration to give a total net emissions of 67.9 GtCO2eq/yr. 

Animal agriculture generates 76% of the food system and 48% of total emissions. 

Human food and waste generate up to 70% of global anthropogenic methane production. 

The conversion of the entire fossil fuel sector to renewable energy WILL NOT REMOVE ANY GHG from the atmosphere.  It would dramatically reduce emissions.  Biomass and biofuels produce at least double the GHG emissions of fossil fuels.  

All GHG emissions in the atmosphere can be sequestered by converting to a vegan diet and reforesting 41% of the land currently used for grazing.

Part 1 – Introduction to Climate Change and Animal Agriculture 

In order to understand how and why animal agriculture is such a major contributor to climate change we start off with some background information on the carbon cycle, the current global emissions, global warming potential, and look at the sources of the emissions that drive climate change.  We then look more closely at a series of research papers that present a range of estimates of the contribution of animal agriculture to climate change and the current global climate change solutions.  Finally we show how veganism and reforestation can completely reverse climate change while restoring biodiversity and wild ecosystems.   

The Carbon Cycle 

Carbon is one of the key elements of life on Earth. Our bodies have carbon and we eat carbon. Our electricity, heating, cooling and transport systems are powered by carbon based fuels.  Carbon is circulated in short cycles (through photosynthesis and respiration) and long cycles (for example through the weathering of rocks formed from the sedimentation of plankton calcium carbonate shells). You can read a fuller description of the Carbon Cycle here. The below diagram shows the stores and flows of carbon. 1 Gt of CO2 is 12/44 Gt of Carbon. 

The below diagram shows a more detailed Carbon Cycle.  

IPCC AR5 Simplified schematic of the global carbon cycle

Numbers give mass of carbon reservoirs in PgC and annual carbon exchange fluxes (in PgC/yr). (1 PgC = 1015 gram C = 1 Gt (billion tonnes) of C).  Black numbers and arrows indicate reservoir mass and exchange fluxes prior to the Industrial Era, about 1750.  Red arrows and numbers indicate annual ‘anthropogenic’ fluxes averaged over the 2000–2009 time period. These indicate the human caused disturbance of the carbon cycle during Industrial Era post 1750. These fluxes (red arrows) are: Fossil fuel and cement emissions of CO2, Net land use change, and the Average atmospheric increase of CO2 in the atmosphere. The uptake of anthropogenic CO2 by the ocean and by terrestrial ecosystems, often called ‘carbon sinks’ are the red arrows part of Net land flux and Net ocean flux.  The change of gross terrestrial fluxes are the red arrows of Gross photosynthesis and Total respiration and fires. 


Current Atmospheric Carbon Dioxide Emissions 

In 2017 the concentration of carbon dioxide (CO2) in the atmosphere reached 407 parts per million (ppm), the highest it’s been in the past 1 to 20 million years.  The annual emissions of anthropogenic Green House Gases (GHG) for 2010 was estimated to be 49 Giga Tonnes of Carbon Dioxide Equivalent (GtCO2eq).  Concentrations of CO2, methane CH4 and nitrogen oxide N2O have increased by 40%, 150% and 20%, respectively since 1750. The following IPCC graph shows the contribution and growth rate of the different GHGs since 1970. 

Potential Future Climate Change Trajectories 

The Climate Action Tracker website states that “In the absence of policies global warming is expected to reach 4.1 °C – 4.8 °C above pre-industrial levels by 2100.  The emissions that drive this warming are called Baseline (or Business As Usual) scenarios and are taken from the International Panel Climate Change Fifth Assessment Report (IPCC AR5). Policies already in place are projected to reduce baseline emissions and result in about 3.6°C warming above pre-industrial levels. The unconditional pledges or promises that governments have made, including the Nov 2016 Nationally Determined Contributions (NDC), would likely limit warming below 3.1°C.”  


Intended Nationally Determined Contributions (INDCs) is a term used under the United Nations Framework Convention on Climate Change (UNFCCC) for reductions in greenhouse gas emissions published in the lead up to the 2015 UN Climate Change Conference held in Paris, in Dec 2015. Under the Paris Agreement, the INDC will become the NDC when a country ratifies the agreement. The NDC will then be the first greenhouse gas targets that apply equally to both developed and developing countries. (Source wikipedia) 

Unfortunately there remains a substantial gap between what governments have promised to do and the total level of actions they have undertaken to date. Both the current policy and pledge trajectories lie well above what’s needed to achieve the Paris goals.  However the IPCC AR5 has shown that substantially more action, sufficient to hold warming below 2°C (and to below 1.5°C by 2100), with likely probability, is technically and economically feasible. According to the IPCC, the costs of reducing emissions to limit warming to below 2°C are modest, even before taking into account co-benefits such as increased energy-security and health improvements due to reduced air pollution (or the trillions of lives saved by plant based agriculture). Annual reductions of consumption growth to pay for the transition are estimated at 0.06% over the century, relative to a projected 1.6 to 3% growth per year. 

Proportion of Climate Change Emissions by Sector 

According to the IPCC  AFOLU is responsible for 24+0.87% of annual GHG emissions. It’s worth noting that this is the current annual GHG emissions and does not show past emissions from previous land use degradation caused by agriculture.  The IPCC shows the impact of different historical emission sources in the graphs of the cumulative emissions. 

Source: IPCC (2014).


Climate Change Greenhouse Gases  

A range of different gases contribute to current GHG emissions.  The main GHG contributions come from carbon dioxide from burning fossil fuels, methane from human and natural sources and carbon dioxide from forestry and land use changes.   

Source: IPCC (2014).


Global Methane Emissions 

The below diagram estimates that anthropogenic sources generate 56% of current methane emissions.   

Source Methane Emissions From Blind Spot to Spotlight, The Oxford Institute for Energy Studies, July 2017

Below is a Schematic IPCC diagram of the global cycle of CH4 showing components from Agriculture and Waste (187-224 Tera grams (Tg)). (Tg equals million tons (Mt) of CH4). Numbers represent annual fluxes in Tg(CH4)/yr estimated for the time period 2000–2009 and CH4 reservoirs in Tg (CH4): the atmosphere and three geological reservoirs (hydrates on land and in the ocean floor and gas reserves). Black arrows denote ‘natural’ fluxes since 1750, red arrows anthropogenic fluxes, and the light brown arrow denotes a combined natural + anthropogenic flux.  Livestock emissions are responsible for 87-94 Tg.  Methane emissions have increased by 150% since 1750. 

IPCC AR5 Simplified schematic of the global methane cycle.  

Below is a breakdown of the different sources of methane. This shows that agriculture is responsible for 53%, fossil fuels for 27% and wastewater and landfills for 20% of global anthropogenic methane production.  Animal agriculture is directly responsible for 33%.  


The production and consumption of food by humans and the waste this generates could be responsible for as much as 70% of global anthropogenic methane production.

A 2017 study estimated the global livestock CH4 emissions were 11% greater (in 2011) than that obtained using the IPCC 2006 emissions factors, encompassing an 8.4% increase in enteric fermentation CH4 and a 36.7% increase in manure management CH4. The authors of this report suggest that livestock methane emissions “may be a major contributor to the observed annual emissions increases over the 2000s to 2010s“. 

A recent Research Paper by Andy Reisinger and Andy Clark of the New Zealand Agricultural Greenhouse Gas Research Centre, explores the question, How much do direct livestock emissions actually contribute to global warming?  They employed “a simple carbon cycle-climate model, historical estimates and future projections of livestock emissions to infer the fraction of actual warming that is attributable to direct livestock non-CO2 emissions now and in future, and to CO2 from pasture conversions, without relying on GWPs.” 

What they found was that “direct livestock non-CO2 emissions caused about 19% of the total modelled warming of 0.81°C from all anthropogenic sources in 2010. CO2 from pasture conversions contributed at least another 0.03°C, bringing the warming directly attributable to livestock to 23% of the total warming in 2010.” 

Comparing GHG Emissions of Different Food Types 

Animal products from dairy to beef produce 36 to 440 times more GHG emissions per Kcal of food energy than pulses, which are an incredibly healthy low fat product that sequester nitrogen into soil and so don’t need any high emission polluting fertilisers. 

Animal products from eggs to beef produce 42 to 382 times more GHG emissions than legumes per gram of protein. 

Global Warming Potential 

The capacity of different greenhouse gases to trap heat in the atmosphere is described in terms of their global warming potential (GWP), which compares the warming potential of different gases to that of CO2 (which has a GWP of 1).  “In the IPCC AR5, methane has a lifetime of 12.4 years and with climate-carbon feedbacks a global warming potential of 86 over 20 years and 34 over 100 years in response to emissions. Model choices such as the time horizon greatly affect the numerical values obtained for carbon dioxide equivalents. The change in time horizon from 20 to 100 years as selected by the IPCC in their mathematical model, decreases the GWP for methane by a factor of approximately 2.5. If we chose a 20 year time horizon this would change the influence of methane in GHG emissions from 16% to 40%.  As a result of methane’s short half-life as compared to CO2, eliminating animal agriculture and food waste would reduce GHGs more quickly.  Reforestation could then take place on the grazing land to sequester the existing emissions as outlined by Jain and Shu in Part 4.  

For this reason Reisinger and Clark concluded that “Our estimates demonstrate that expanding the mitigation potential and realizing substantial reductions of direct livestock non-CO2 emissions through demand and supply side measures can make an important contribution to achieve the stringent mitigation goals set out in the Paris Agreement, including by increasing the carbon budget consistent with the 1.5°C goal.” 

Summary of Research Findings 

Animal products from dairy to beef produce 36 to 440 times more GHG emissions per Kcal of food energy and 42 to 382 times per gram of protein than pulses.  Animal agriculture is responsible for 33% of global anthropogenic methane emissions. Agriculture is responsible for 53% and wastewater and landfills a further 20% of global anthropogenic methane emissions. A 2017 study estimated that the global livestock CH4 emissions were 11% greater (in 2011) than estimated using the IPCC 2006 emissions factors.  Another study estimated that “direct livestock non-CO2 emissions caused about 23% of the total modelled warming in 2010”. If the IPCC chose a 20-year time horizon the proportion of GHG generated by methane would increase from 16% to 40%. Because of methane’s short half-life, phasing out animal agriculture would reduce GHGs from methane more quickly and at a fraction of the cost compared with measures involving renewable energy and energy efficiency investments.  But extensive sequestration will still be needed.  For that The Lifestyle Carbon Dividend research paper (see reports below) calculates that climate change can be completely reversed by a transition to a vegan diet combined with the reafforestation of 41% of the land previously cleared for animal agriculture.   

If that wasn’t enough a recent Report produced by GRAIN, the Heinrich Boll Foundation and the Institute for Agriculture and Trade Policy Europe calculated that the top 20 meat and dairy companies emit more GHG than Germany.  The report titled, Big Meat and Dairy’s Supersized Climate Footprint, calculated that the top five meat and dairy companies emit more GHGs than Exxon or Shell or BP.  In this report the authors also calculated that Business As Usual Meat and Dairy production will make meeting Paris Climate Goals impossible (also noted in Springman and the Chatham House Reports outlined below). 


Without doubt the sustainable and manageable level of animal and fish production on planet Earth today is precisely ZERO.  Small farmers already produce 70% of the world’s food. A transition to plant based organic agricultural system based on small scale farms selling unprocessed food directly to local consumers will maximise the financial returns for farmers. In the next section we will highlight the approach used by the IPCC in calculating the emissions of AFOLU and estimate what the actual contribution of animal agriculture is to climate change. 


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