Could reintroducing wildlife in northern Siberia slow global warming?
The idea is that wild horses, moose and reindeer, perhaps followed by
other deer and bison, would slow global warming. Grazing and trampling
would encourage the growth of grass. Trampling herds would compress
the snow and the soil, creating an insulator that prevents the soil
from thawing and that keeps permafrost frozen. Furthermore, grass and
snow will reflect sunlight more, as opposed to darker-colored tundra
and forest that would absorb more sunlight.
Questions:
1. Would above benefits be outweighed by the fact that grazing animals
would cause additional emissions, through digestion and through their
manure?
2. Would grassland indeed form, or would compressing the soil due to
trampling instead contribute to the formation of swamps and wetlands
that cause additional emissions?
What's you view? Is grassland a better alternative than tundra and
forest? Is this initiative to be recommended?
Cheers,
Sam Carana
As an example, this report in the Guardian dates back to July 13, 2009:
http://www.guardian.co.uk/environment/2009/jul/13/manchester-report-grasslands
The report was recently referred to in a summary of geo-engineering
proposals, at:
http://www.guardian.co.uk/environment/2011/feb/18/geo-engineering
Supporters of grazing sometimes refer to a study at the University of
Sydney that said that "while cows might emit 54kg of methane per head
per year, oxidising bacteria in high country soils can oxidize methane
at the rate of 8760kg for every hectare each year."
http://www.theaustralian.com.au/business/industry-sectors/a-hiccup-in-the-cow-burp-theory/story-e6frg976-1225791141055
http://theland.farmonline.com.au/news/nationalrural/agribusiness-and-general/general/ets-lifeline-soils-capable-of-absorbing-cattle-methane/1612492.aspx
In hindsight, it turned out that an error had been made and that the
soil "methane oxidation rate measured by University researchers is
actually 8.75 kilograms per hectare per year."
http://theland.farmonline.com.au/news/state/agribusiness-and-general/general/error-in-snowy-soils-carbon-report/1887462.aspx
That makes it hard to keep cows on the land and remain
methane-neutral, given that the study found that "cows might emit 54kg
of methane per head per year". Cows often require extra feed, which is
typically produced by using fertilizers that can cause N2O emissions,
require water, energy and further land, and may drive up the price of
food for human consumption.
Not only is it hard to keep ensure that cattle have enough grass to
eat, the land also needs to be looked after, to avoid pests,
wildfires, etc. The study used an example of grazing area made up of
49% woodlands, 49% grassland and two per cent bog. However, such
ratios change, which can cause additional emissions. When there's lots
of rain, the bog area will grow. Conversely, when there's drought,
wildfires may occur. To avoid wildfires, it makes sense to regularly
clean up surplus biomass from the land, and preferably dealt with in
other ways than to simply burn it on the spot. Good land management
can avoid many emissions otherwise caused by wildfires, droughts,
flooding and erosion.
So, if surplus biomass is to be removed from the land anyway, it might
as well be pyrolyzed. And if the infrastructure for pyrolysis should
be in place anyway, then why have cows to do something that could be
better done through collection of biomass and pyrolyzing it? In other
words, if pyrolysis does indeed do a better job, then why have cows?
Cheers!
Sam Carana
On Wed, Jan 19, 2011 at 4:16 PM, someone wrote:
> "grazing animals would cause additional emissions, through digestion and
> through their manure?"
>
> The emissions come from the mineralization of organic matter by
> microorganisms. This happens no matter whether the organic matter passes
> through an animal gut or not. If you don't want emissions then don't grow
> any plants, but then you will also not draw down any atmospheric gasses.
> It's a cycle.