Of course, it's not what the earth already emits naturally, it's the
effect of what humans have added that should be our concern. However
there is some data about termites:
<quote>
However, data indicate that while there are large variations in the
amount of CH4 produced by different species, the total methane source
due to termites is probably less than 15 Tg per year, thus making a
contribution of less than 5% to global CH4 emissions.
</quote>
The IPCC reports http://www.epa.gov/methane/sources.html
Wetlands. Natural wetlands are responsible for approximately 76% of
global methane emissions from natural sources, accounting for about
145 Tg of methane per year. Wetlands provide a habitat conducive to
methane-producing (methanogenic) bacteria that produce methane during
the decomposition of organic material. These bacteria require
environments with no oxygen and abundant organic matter, both of which
are present in wetland conditions.
Termites. Global emissions of termites are estimated to be about 20 Tg
per year, and account for approximately 11% of the global methane
emissions from natural sources. Methane is produced in termites as
part of their normal digestive process, and the amount generated
varies among different species. Ultimately, emissions from termites
depend largely on the population of these insects, which can also vary
significantly among different regions of the world.
Oceans. Oceans are estimated to be responsible for about 8% of the
global methane emissions from natural sources, accounting for
approximately 15 Tg of methane. The source of methane from oceans is
not entirely clear, but two identified sources include the anaerobic
digestion in marine zooplankton and fish, and also from methanogenisis
in sediments and drainage areas along coastal regions.
Hydrates. Global emissions from methane hydrates is estimated to be
around 10 Tg of methane per year, accounting for approximately 5% of
the global methane emissions from natural sources. Methane hydrates
are solid deposits composed of cages of water molecules that contain
molecules of methane. The solids can be found deep underground in
polar regions and in ocean sediments of the outer continental margin
throughout the world. Methane can be released from the hydrates with
changes in temperature, pressure, salt concentrations, and other
factors. Overall, the amount of methane stored in these hydrates
globally is estimated to be very large with the potential for large
releases of methane if there are significant breakdowns in the
stability of the deposits. Because of this large potential for
emissions, there is much ongoing scientific research related to
analyzing and predicting how changes in the ocean environment affect
the stability of hydrates.
And http://www.agu.org/sci_soc/prrl/prrl0231.html
In a baseline study in 1995, 60 percent of methane emissions to the
atmosphere were the result of human activity. The IPCC's A1 scenario,
which Fiore characterizes as "less optimistic in terms of anticipated
emissions than a companion B1 scenario," posits economic development
as the primary policy influencing future trends of manmade emissions
in most countries. Under A1, emissions would increase globally from
1995 to 2030, but their distribution would shift. Manmade nitrogen
oxides would decline by 10 percent in the developed world, but
increase by 130 percent in developing countries. During the same
period, methane emissions would increase by 43 percent globally,
according to the A1 scenario.
and http://www.climatescience.gov/infosheets/highlight1/default.htm
Human-influenced sources of methane include landfills, natural gas and
petroleum production and distribution systems, agricultural
activities, coal mining, stationary and mobile combustion, wastewater
treatment, and certain industrial processes. About 60% of global
methane emissions come from these sources and the rest are from
natural sources (IPCC, 2001). Natural sources include wetlands,
termites, oceans, and hydrates (which consist of methane molecules
each surrounded by a cage of water molecules and are present in
seafloor deposits around the world).
As far as trees are concerned, this is based on a recent study and is
yet to be confirmed, nevertheless
<quote>Consensus
The study does not seek to explain exactly how the methane is emitted,
nor suggest which plant species may emit more than others.
Nor does it challenge scientific opinion on global warming, which has
become rock-hard over the past five years and is now questioned only
by a small minority.
The consensus is that global warming is a fact and may already be
affecting Earth's climate, and the big culprit is the billions of
tonnes of CO2 spewed out by burning oil, gas and coal.
The paper's earliest impact could be political, for it attacks one of
Kyoto's conceptual cores.
Under the protocol's notoriously complex rule book, industrialised
signatories that plant forests can offset the supposed benefit against
their national quotas of CO2. </quote>
So these findings may be used politically to counter the Kyoto
protocol as trees were seen as a way to offset CO2 sources.
Keppler, the originator of the study warns
<quote>Keppler cautions against 'over interpreting' his results. He
warns that it is not only net emissions from trees that need to be
re-evaluated. Rising temperatures caused by greenhouse gases, and
changing atmospheric conditions caused by changing carbon dioxide
concentrations will lead to increased methane emissions from plants
and emphasise global warming, he told Chemistry World. 'This effect
could be much more pronounced than the benefit you get from other
[reforestation] programmes,' he said. </quote>
Global Warming - The Blame Is not with the Plants
International scientific team reacts to misinterpretation of their
research results and provides the correct perspective
On 1/9/07, Janice Matchett <janmatch@earthlink.net> wrote:
>
> At 05:11 PM 1/9/2007, Lawrence Johnston wrote:
>
> "..I have also read that termites similarly produce methane, probably by
> synrgistic cellulose digesting bacteria. Does anyone have an estimate of
> how much of the greenhouse gases come from this source?
>
> @ Termites emit 20 million tons of methane per year. (See Nature, Vol 439,
> pg. 148).
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Received on Wed Jan 10 01:05:16 2007
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