Re: (Fwd) [asa] Cows, diet, and warming

Termites, ruminants such as cows and sheep, shipworms (wood-boring
bivalves), and any other animal that digests cellulose does so with
the help of symbiotic protists and bacteria. They thus have fairly
similar digestive processes and may all be expected to produce some
methane. However, the exact microbial flora varies, so the methane
production by any one host will vary.

There are numerous bacteria that use methane as an energy source,
They produce carbon dioxide and water, so they aren't exactly
eliminating greenhouse issues, but methane is a relatively strong
greenhouse gas.

In addition to the question of balance, there is the issue of rate.
Humans are relatively rapidly causing changes in gas concentrations,
average temperature, etc. To take the sink metaphor again, if the
inflow increases slowly, it is less difficult to adjust and reach a
new balance than if the inflow increases rapidly. The same final
amount might be reached in either case, but whether everything else
has kept up is an issue.

It's also worth noting that just because a value falls within the
natural range of variation does not prove it is an acceptable level
for humans to generate. An obvious example is that most people would
object to pollution that produced light levels at noon that are
normally encountered at midnight. More subtle is the tendency of
humans to change an environment so that it does not correspond to the
natural conditions, even though the values fall within the natural
range. For example, releasing cold, deep water from large dams
probably stopped reproduction in many freshwater mussels downstream
because it seems to the mussel like it's always winter.

-- 
Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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