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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

What the science says...

Animal agriculture is responsible for 14–18% of human-cau

The burning of fossil fuels for energy and animal agriculture are two of the biggest contributors to global warming, along with deforestation. Globally, fossil fuel-based energy is responsible for about 60% of human greenhouse gas emissions, with deforestation at about 18%, and animal agriculture between 14% and 18% (estimates from the World Resources Institute, UN Food and Agriculture Organization, and Pitesky et al. 2009).

So, animal agriculture and meat consumption are significant contributors to global warming, but far less so than fossil fuel combustion. Moreover, fossil fuels are an even bigger contributor to the problem in developed countries, which use more energy and have increased livestock production efficiency (Pitesky et al. 2009). For example, in the United States, fossil fuel-based energy is responsible for about 80% of total greenhouse gas emissions as compared to about 6% from animal agriculture (estimates from the World Resources Institute and Pitesky et al. 2009).

How does animal agriculture cause global warming?

On of the main ways in which the livestock sector contributes to global warming is through deforestation caused by expansion of pasture land and arable land used to grow feedcrops. Overall, animal agriculture is responsible for about 9% of human-caused carbon dioxide emissions globally (UN FAO).

Animal agriculture is also a significant source of other greenhouse gases. For example, ruminant animals like cattle produce methane, which is a greenhouse gas about 20 times more potent than carbon dioxide. The livestock sector is responsible for about 37% of human-caused methane emissions, and about 65% of human nitrous oxide emissions (mainly from manure), globally (UN FAO).

Beef is a bigger problem than other sources of meat

Producing beef requires significantly more resources (e.g. land, fertilizer, and water) than other sources of meat. As ruminant animals, cattle also produce methane that other sources (e.g. pigs and chickens) don't.

Eschel et al. 2014 estimated that producing beef requires 28 times more land, 6 times more fertilizer and 11 times more water than producing pork or chicken. As a result, the study estimated that producing beef releases 4 times more greenhouse gases than a calorie-equivalent amount of pork, and 5 times as much as an equivalent amount of poultry.

Eating vegetables produces lower greenhouse gas emissions yet. For example, potatoes, rice, and broccoli produce approximately 3–5 times lower emissions than an equivalent mass of poultry and pork (Environmental Working Group 2011). The reason is simple – it's more efficient to grow a crop and eat it than to grow a crop, feed it to an animal as it builds up muscle mass, then eat the animal.

Environmental Working Group GHG Lifecycle Assessment of foods

Greenhouse gas lifecycle assessment for common proteins and vegetables (EWG 2011).

Updated on 2015-11-26 by dana1981.

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What the science says...

How does animal agriculture cause global warming?

Beef is a bigger problem than other sources of meat