Friday, November 4, 2016

Modern Day Cattle Haven't Increased Greenhouse Emissions Over Ruminant Emissions 500 Years Ago

A pile of American bison skulls waiting to be ground for fertilizer, mid-1870s.

I have previously questioned the prevailing media mentality of blaming cattle for increased greenhouse emissions. See here and here.

The media goes on and on about this. A few days ago, we got this from Inhabitat, "Methane is 36 times more damaging to the environment than carbon dioxide, and livestock are responsible for emitting 44 percent of the greenhouse gas around the globe. Fortunately, a team of Australian scientists discovered that adding dried seaweed to sheep and cattle feed can cut global methane emissions by 70 percent – which is the equivalent of eliminating India’s nationwide carbon dioxide emissions. Rocky De Nys is a professor of aquaculture at James Cook University (JCU), and he has been leading the efforts to develop a seaweed-infused cattle feed that could fight climate change and help save the world." My B.S. meter just went off, how about yours? I have to wonder how much the author knew about the science of greenhouse gases OR cattle. The oft-repeated stat is "About 44 percent of livestock emissions are in the form of methane", a far different meaning from Inhabitat saying that livestock are responsible for 44 percent of emissions.

This week, I received the following from astute reader RJS, who presents some sanity to this subject in a way I haven't seen done before.

RJS:
The article, Groups Sue Government Over Slaughter of Yellowstone Bison, says there were once 60 million bison in the prairies and grasslands of North America. That compares with 93 million cows in the U.S. today. Since the eastern forests were populated by deer and antelope at the same time as the bison roamed the plains, we might assume there has not been an appreciable increase in methane emissions from ruminants over the history of this continent.

More from RJS:
The point is that emissions from ruminants today aren't much different than they were 500 years ago, as we've stayed near the limit of how many animals that the land mass of North America can support over most of our history. Moreover, carbon emissions from animals are all part of the surface carbon cycle. CO2 is absorbed by plants, eaten by animals, which in turn emit the carbon as CO2 and methane, which eventually degrades back to CO2. Agriculture does not introduce new carbon into the atmosphere that wasn't there at some time in our planet's recent history (nitrous oxide from fertilizer is another matter). The total carbon in the surface carbon cycle remains constant, in whatever form it takes, whether it's part of plants, animals, decaying matter, dissolved in water, in the soil, or in the air. Coal and oil, on the other hand, are from deposits of carbon that have been locked up underground for millenniums, and when they're burned, they add carbon to the atmosphere that wasnt there before, at least not in our geologic timeframe. So it's the extraction & burning of fossil fuels that put new carbon into the surface carbon cycle, not the food that we're eating.

3 comments:

  1. How about carbon sequestration in the soil that is extracted through intensive agriculture to feed and sustains the growing world population. Obviously we are harvesting way more than we used to harvest 500 years ago. If agriculture is a simply a mechanism and flow of carbon, then why are we so concern about the deforestation. It does not change the total mass of carbon on earth. It just changes from one location to another or from one form to another.

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  2. Thanks for your comment. First, agriculture has unleashed a lot of carbon, especially where land use changes have occurred such as wetlands and swamps converted to growing crops, such as forests converted to farmland, such as grasslands converted to annual cornfields or other annual crops. When bison roamed America grasslands sequestered carbon and if you read the articles linked at the top, one explains how regenerative farming techniques using rotational grazing today could help sequester carbon and so livestock, or ruminants are an important part of the carbon sequestering plan for agriculture since they help fertilize the soil without using fossil fuels. What RJS omitted was the amount of fossil fuels used in today's intensive farming systems in tractors, transport, and modern energy inputs in addition to Nitrogen fertilizer. The food grown also requires enormous amounts of fossil fuel energy to store, refrigerate, process, and package for use by humans in our anthropocene era.

    The carbon cycle of trees is so much longer than the carbon cycle of annual crops, and serves as a constant carbon sink.

    You asked a good question and I hope others will weigh in.

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  3. Interesting that this week, Britain's Sustainable Food Trust held a conference (Prince of Wales attended, too). Joel Salatin was a main speaker and he kicked of his first talk by saying that "500 years ago the US had more grazing animals than it does today, despite the rise of intensive feedlot agriculture" which was from live blogging on twitter.

    Coincidence, or??

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