Guest Post by Geoff Russell.
Geoff is a mathematician and computer programmer and is a member of Animal Liberation SA.
This second part will cover chapter 3 of Livestock’s Long Shadow (LLS), which concern livestock’s direct impact on the climate via forcings and its impact on air. It will be more concise than PART I.
Quickly recapping on the previous post. Producing animals for food consumes the output of 1/3 of all arable land + a grazing area of 3,400m ha, which is about 4.5 times the size of Australia + the entire and declining output of global ocean and freshwater fisheries + aquaculture output. The net result is foods that constitute 17% of global calories.
This post isn’t about protein, but whenever anybody mentions the high cost of producing animal foods, the response is quicker than a knee jerk and more reliable:”but we need the protein.” I dealt with this a little in the previous post, and I’ll deal with it a little more at the end of this one. But lets move on.
A forcing, as frequent readers of Barry’s blog will understand is anything which changes the planet’s energy budget. Which means it changes the energy arriving or the energy leaving the planet. Not all forcings are greenhouse gases. Forcing is measured in watts per square metre.
Something like ice is a forcing because its area (currently!) is huge and it effects how much of the sun’s radiation simply “bounces off” and doesn’t heat up the planet. RealClimate last year published a piece (on 1st of April) 2007 on a plan to solve the climate change problem by covering the planet in billions of sheep, which, being white, would reflect more energy and solve all our problems.
A particularly complex janus faced forcing are the aerosols. These are tiny particles in the air and can be either warming, like the black carbon from a bush fire, or cooling, like sulphate emissions given off when coal is burned.
Chapter 3 of LLS examines direct (and not so direct) livestock impacts on climate change and air pollution. They consider carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) with the 3 biggest contributors being deforestation, enteric fermentation and manure.
• Deforestation produces primarily CO2 and contributes 34% of the livestock impact.
• Manure produces both methane and a nitrous oxide and contributes 30.2% of the total livestock CO2eq.
• Enteric fermentation produces methane and contributes 25% of the total livestock CO2eq.
The remaining factors are just small change. If methane were accorded its full warming impact, then enteric fermentation would exceed deforestation as a climate forcing. Between 1750 and 2000, atmospheric CO2 rose about 30% while atmospheric methane rose 150%. But this is misleading because all the methane currently in the atmosphere was put there in the past couple of decades, where as plenty of the CO2 was put their by people long since dead.
LLS estimates that livestock is responsible for 35-40% of all anthropogenic methane emissions.