The True Impact of Diet on Climate

Animal agriculture has a major effect on our environment and our climate. Consider these recently reported statistics;

Animal agriculture is the second largest contributor to human-produced greenhouse gas emissions after fossil fuels. It contributes between 14.5% and 18% of global GHG emissions (7.1 billion metric tonnes of CO2 equivalent) annually. This is similar to the emissions from all the fuel burned by all the world’s transport vehicles, including cars, trucks, trains, boats and airplanes (1,2).

Animal agriculture uses a third of the planet’s ice-free land surface (3).

Animal agriculture uses 16% of global freshwater (4).

Animal agriculture is linked to 75% of the historic deforestation in the Brazilian Amazon rainforest and nearly a third of biodiversity loss (5).

Animal agriculture is a leading cause of air pollution (1).

One-third of worldwide grain production is used to feed livestock (6).


Shocking as they seem, even these alarming statistics may be severely underestimating the damaging effect on our planet from the production of animals for food. In November of 2019, Dr. Sailesh Rao and his colleagues released a White Paper in which they outline their argument that the widely accepted statistic that livestock production is responsible for 14.5% of greenhouse gases is a dangerous understatement that, if left unchallenged, will sabotage any efforts to reverse climate change (7). Since 2006, Dr Rao has been studying the environmental crises affecting humanity and how to reverse them. He is the Founder and Executive Director of the non-profit organization, Climate Healers, with its objective to implement a holistic, grassroots solution to climate change.


Before going any deeper into this topic we need to understand a bit about greenhouse gases (GHG), gases in the atmosphere that trap heat. The gases that make up GHG are;

Carbon dioxide (CO2) which comes from burning fossil fuels (coal, oil and natural gas), solid waste, trees and other biological materials. Carbon dioxide can be removed from the atmosphere through absorption by plants. This is known as “sequestration”.

Methane (CH4) which is produced by livestock and other agricultural activities; during the production and transport of coal, oil and natural gas; and by the decay of organic waste (dumps, landfills).

Nitrous oxide (NO2) which is emitted during agricultural and industrial actions, treatment of wastewater and combustion of fossil fuels.

Fluorinated gases (hydrofluorocarbons, perfluorocarbons, sulphur hexafluoride, nitrogen trifluoride) which come from various industrial activities. These gases are often used as substitutes for stratospheric ozone-depleting substances like chlorofluorocarbons, hydrochlorofluorocarbons and halons. Fluorinated gases are produced in smaller quantities than the other GHG but have more potent effects.

Environmental effects of each of these gases depend on their ability to warm the planet through absorption of energy (Global Warming Potential (GWP)), the amount of them in the atmosphere and the length of time they remain in the atmosphere. Regardless of their source, GHG mix in the atmosphere and their individual concentrations are fairly equal around the globe (8).


Dr. Rao’s White Paper sets out to present the results of a Global Sensitivity Analysis that proves that animal agriculture is the leading cause of climate change, responsible for 87% of human-made GHG emissions (7). Though the burning of fossil fuels is currently the leading source of human-made CO2 emissions, this paper asserts that it is the cumulative human-made GHG gas emissions that must be considered. Human beings have burned fossil fuels for a little more than 200 years, but we have been burning down forests for livestock production for over 8000 years and this must also be taken into account. Data used in this White Paper comes from the Fifth Assessment Report of the Intergovernmental Panel of Climate Change (IPCC) (9) and other peer-reviewed scientific research. This White Paper concludes that concentrating on the reduction or elimination of fossil fuel usage will actually accelerate warming of the planet, potentially to the point of no return. Why? Because the annual methane emissions from animal agriculture alone result in more global warming than the annual CO2 emissions from all fossil fuel sources combined.


How does this report come up with such a high number for the GHG derived from animal agriculture? The researchers point out the following significant miscalculations in the United Nations (UN) Intergovernmental Panel on Climate Change (IPCC) reports which result in the underestimation of the impact of livestock on climate change (7).

1 The IPCC uses total CO2 emissions instead of the amount of CO2 that remains airborne. Less than half of CO2, about 45%, remains in the atmosphere. This means that fossil fuels are taking the blame for more than their share of global warming.

2 The IPCC underestimates the impact of methane by using a 100-year time frame for their calculations. Methane gas lingers in the atmosphere for about 10 to 12 years before its reactions with oxygen free radicals result in its conversion into CO2. While the GWP of methane over 100 years is 28 times that of CO2, its value over 10 years is 130. This means that methane gas in the atmosphere has 130 times the global warming ability as the same amount of CO2 over 10 years. It is the 10-year GWP value that must be considered since catastrophic climate change looks to be imminent within the next eleven years (13).

3 The IPCC does not consider the costs of the land use changes required for animal agriculture. When forests are destroyed to create grazing land, the ability of that land and its vegetation to absorb CO2 is gone as well.

4 The IPCC uses raw data from the animal agriculture industry itself, obviously not a neutral source.


To respond to this high production of GHG from livestock, Dr. Rao and his team propose a worldwide transition to a plant-based economy which has the potential to sequester over 2 trillion metric tonnes of CO2 in regenerating soils and vegetation and to lower atmospheric GHG levels to below 350 parts per million of CO2 equivalent (the “safe zone”). Moreover, they predict that this step would restore the biodiversity of the planet and heal our climate. Since animal agriculture is the leading cause of climate change, diets relying entirely on plant-based foods and avoiding animal-based foods are a much more immediate and practical mitigation strategy than trying to eliminate fossil fuel burning (7).


The Rao White Paper is not the first research to suggest that the climate effect of food animal production has been underestimated. In the November/December 2009 issue of World Watch Journal, Robert Goodland and Jeff Anhang, both advisers to the World Bank, published the alarming estimate that at least 51% of global GHG emissions are attributable to the life cycle and supply chain of livestock products. These authors conclude that replacing animal-based products with better alternatives would be the best strategy for reversing climate change, and would in fact be an approach that would have far more rapid effects on GHG emissions and their atmospheric concentrations than actions to replace fossil fuels with renewable energy (10). In February of 2019 another report was published in The Lancet in which leading environmental and nutritional researchers reviewed the effects of food production on human health and the health of the environment. Their recommendations were that shifting the human diet toward plant foods and away from animal products is vital for both human health and the health of our planet. Their investigations found that food production is responsible for up to 30% of total GHG emissions and that animal products account for about 75% of these emissions (or 22% of total GHG emissions). Diets eliminating meat are associated with the greatest reductions of GHG emissions. Additionally, such a policy would reduce the excessive use of freshwater and ice-free land use by food animals as well as reduce hunger and increase human health worldwide (11).


Whether the true consequence of animal agriculture on our climate is the production of 14.5% or 18% or 22% or 51% or 87% of total GHG emissions, it is clear that our present use of animal products for food is a staggering problem for the future of our planet. A 2018 meta-analysis delved into this subject (12). The authors state that trying to feed the 7.6 billion human beings on the earth using current diets and production practices is degrading land and water ecosystems, depleting water resources and driving climate change. In this study, data was gathered from almost 39,000 commercially viable farms in 119 countries and analyzed for the effects on important environmental impact indicators including land use, freshwater usage and GHG production. The researchers point out that, in an ideal world, producers, distributors and retailers could immediately reduce their own influences on the environment with the help of tax breaks or subsidies and consumers would be educated about environmentally friendly products and make their choices accordingly. But such steps are difficult and time-consuming and can only go so far. The bottom line is that the environmental effects of animal products markedly exceeds that of vegetable products. Even buying sustainably sourced meat and dairy cannot outdo the benefits of a plant-based diet. Meat, eggs, dairy and aquaculture use 83% of the world’s farmland and yet they provide only 18% of our calories and 37% of our protein. The lowest-impact animal products still greatly exceed the average impacts of vegetable production in GHG emissions and land use (12).


Results of this meta-analysis were summarized in this way (12);

Transitioning to plant-based diets by consumers would deliver environmental benefits on a scale not achievable by producers. Predicted favourable changes include;

Reduction in land use for food production by 3.1 billion hectares (a 76% decrease)

Reduction in total yearly GHG emissions by 6.6 billion metric tonnes of CO2 (a 49% reduction)

Reduction in freshwater usage by 19%

In addition, the land no longer needed for food production could remove 8.1 billion metric tonnes of CO2 from the atmosphere each year if natural vegetation is re-established. In North America, where meat consumption is three times the global average, dietary change has even greater potential for positive transformations with a conceivable reduction of GHG emissions by 61 to 73%.

Large environmental benefits could ensue even from just cutting down on animal products. A worldwide 50% reduction in animal-sourced food consumption might achieve up to 73% of the reduction in GHG emissions from an entirely plant-based diet (12).


Perhaps studies and reports like these will bring awareness to the human population on this planet about the damage that simple food choices can create and encourage us to consider the health of our environment when making decisions on what we are going to consume.



1 Livestock’s Long Shadow: Environmental Issues and Options. The Livestock Environment and Development Initiative (LEAD). Food and Agriculture Organization of the United Nations (FAO)

2 Gerber, P.J., Steinfeld, H., Henderson, B., Mottet, A., Opio, C., Dijkman, J., Falcucci, A. & Tempio, G. Tackling climate change through livestock – A global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations (FAO), 2013, Rome.

3 Foley, J., Ramankutty, N., Brauman, K. et al. Solutions for a cultivated planet. Nature. 2011; 478:337–342.

4 Mekonnen, M.M. and Hoekstra, A.Y. (2010) The green, blue and grey water footprint of farm animals and animal products, Value of Water Research Report Series No. 48, UNESCO-IHE, Delft, the Netherlands.

5 Machinovina, B., Feeley, K.J., Ripple, W.J. Biodiversity conservation: The key is reducing meat consumption.
Science of The Total Environment. December 2015; 536: 419-431.

6 Pradhan, P., Lüdeke, M.K.B., Reusser, D.E., Kropp, J.P. Embodied crop calories in animal products. Environmental Research Letters. December, 2013. 8(4).



9 Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

10 Goodland, R., Anhang, J. Livestock and Climate Change. World Watch: November/December 2009.

11 Willett, W., Rockström, J., Loken, B., Springmann, M., Lang, T., Vermeulen, S. et al. Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems. The Lancet Commissions. February 2, 2019; 393(10170): 447-492.

12 Poore, J., Nemecek, T. Reducing food’s environmental impacts through producers and consumers. Science. 2018; 360: 987–992.


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My name is Debra Harley (BScPhm) and I welcome you to my retirement project, this website. Over the course of a life many lessons are learned, altering deeply-rooted ideas and creating new passions.

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