How Much Is Global Warming Due to Animal Agriculture?

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How Much Is Global Warming Due to Animal Agriculture?

[Ed. Note: Read many other articles about the destructive impacts of our food choices on our environment - Environmental Articles. The most powerful thing each person can do to save the planet is to go vegan. Reality statistics back that up!]

By Stephen Kaufman, M.D., Christian Vegetarian Association (CVA)

[This essay was prepared for distribution at the June 2011 General Synod of the United Church of Christ. Comments and suggestions to cva@christianveg.org are appreciated.]

When environmentalists talk about what we need to do address global warming, they rarely emphasize, and often don’t even mention, moving toward a plant-based diet. Yet doing so is one of the most important things each of us can do to reduce our greenhouse gas footprint.

When environmentalists talk about what we need to do address global warming, they rarely emphasize, and often don’t even mention, moving toward a plant-based diet. Yet doing so is one of the most important things each of us can do to reduce our greenhouse gas footprint. The 2006 United Nations Food and Agriculture Organization report Livestock’s Long Shadow concluded that animal agriculture is responsible for 18% of human-derived greenhouse gasses – more than cars, trucks, and airplanes combined.

Actually, this 18% figure might be a gross underestimate. A 2009 analysis by Robert Goodland and Jeff Anhang published in World Watch entitled “Livestock and Climate Change” concluded that at least 51% of human-derived greenhouse gasses derive from animal agriculture. By necessity, this report included estimates, and I offer a brief critical review of Goodland and Anhang’s article. I conclude that there is good reason to believe that far more than 18% of human-derived greenhouse gasses come from animal agriculture.

The Analysis

Many gasses have different degrees of greenhouse effects, that is, they trap heat leaving the earth and give the atmosphere its warmth. In order to “compare apples to apples,” the FAO calculated the greenhouse effect potency of different gasses compared to CO2, or “CO2 equivalents” (CO2e). The FAO estimated that animal agriculture adds 7,516 million tons of CO2e to the atmosphere each year. Goodland and Anhang argued that the FAO did not include 8,769 million tons CO2e added to the atmosphere by livestock breathing out CO2. The FAO did not include this source of CO2 because the amount of CO2 that farmed animals breathe out is roughly equivalent to the amount of CO2 taken from the atmosphere by the plants which the animals eat. However, if the farmed animals had not eaten those plants, there would be a steady increase in CO2 sequestration as farmland returned to forests. Further, continued intensive farming designed to provide feed for farmed animals releases carbon sequestered in soil.

Methane is a much more potent greenhouse gas than CO2, but it has a significantly shorter half-life in the atmosphere. The FAO calculation adjusted methane to a CO2e value by lowering methane’s short-term impact but lengthening the methane effect over a longer duration. However, by reducing the short-term CO2e for methane, the FAO did not account for global warming positive feedback loops. For example, as methane and other greenhouse gasses increase global temperatures, polar ice melts. This converts ice, which reflects 70-80% of the sun’s light back into space, into water, which absorbs most of the sun’s light energy and reflects less than 10%. Warmer water and air then melt more ice. Goodland and Anhang’s adjustment for methane increased its CO2e by 5,047 million tons annually.

There are several other considerations, of which I will mention a few. Goodland and Anhang noted that the FAO used 2002 data on world tonnage of farmed animals, but this tonnage has increased rapidly since then. They estimate that the growth of the tonnage of farmed animals has contributed an additional 2,560 million tons CO2e. Goodland and Anhang also noted that the FAO overlooked other significant sources of greenhouse gasses attributable to animal agriculture, including farmed fish; fluorocarbons to cool meat, dairy, and eggs; cooking (meat typically entails higher temperatures and longer durations than plant foods); disposal of liquid and solid wastes of livestock; production, distribution, and disposal of packaging for animal products (which for sanitary reasons is generally much more extensive than for plant-based products); and carbon-intensive medical treatment of diseases related to consuming animals, including infectious organisms derived from farmed animals, and heart disease and other conditions related to consuming animal products. Goodland and Anhang estimated that these other categories add over 8,500 million tons CO2e annually.

I think that it is clear that, if we aim to avert an environmental crisis due to global warming, moving toward a plant-based diet must be a part of the effort.