| Yes but the grasslands the cows graze on will easily mop up all that excess carbon. And the point of the article is that you can't have plant only edible calories. A calorie of meat is not the same as a calorie of plant. It's just a unit of energy and too simplistic a measure to compare with. ‘BUT’ – I hear you say… “Cows burp and fart too much which is causing climate change and we can’t feed 8 billion people from this ‘out of date’ system – the world’s different now!”. Once upon a time in the USA there used to be a vast area of prairie (pasture) called the Great Plains. This story can be replicated on any of the world’s grasslands. This vast grassland was a giant ‘carbon sink’ with deep soils of up to 15% organic matter and was a rich habitat for thousands of different species of flora and fauna. Even through severe droughts, the plains supported somewhere in the region of 110 million wild ruminants. 50-70 million of those were the giant one-tonne bison – the equivalent to about 2 small beef steers. We now, in the USA, have roughly the same number of domestic ruminants. 1 Wild animals burp and pump too! So how come pre-industrialisation these ‘evil’ ruminant beasts didn’t wreck our climate? Healthy soils contain soil microbes called methanotrophs that reduce atmospheric methane. So the grassland on which the cattle are grazing can absorb a large amount of the methane they produce. The highest methane oxidation rate recorded in soil to date has been 13.7 mg/m2/day (Dunfield 2007) which, over one hectare, equates to the absorption of the methane produced by approximately 100 head of cattle! 2, 3 ‘Methane sinks’ bank up to 15% of the earth’s methane. Converting pasture into arable production reduces the soil’s capacity to bank methane and releases carbon into the atmosphere. Fertilising and arable cropping reduce the soils methane oxidation capacity by 6 to 8 times compared to the undisturbed soils of pasture. The use of fertilisers makes it even worse, reducing the soils ability to take up methane even further.4, 5, 6 So to convert pasture to arable land in a ‘quick fix’ to try and grow more plant-based foods considerably accelerates the climate change situation. And anyway let’s put enteric methane (cow burping methane) into context. According to the 2014 UN Climate Change Convention held in December in Lima, Peru, the analysis of GHG’s when converting other gases to CO2 equivalents found that in the US and EU enteric fermentation accounted for 2.17% of GHG emissions. (26.79% of agriculture emissions with all agricultural emissions in total being 8% of total GHG emissions).7 Have you looked into the methane output of rice paddies recently? |