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Larry Febo wrote:
> I never could understand how "climate" could be considered a causal agent
> in extinction. I mean,....most organisms are quite capable of migrating to a
> more amiable enviorn , ...right???
Not necessarily, no. Actually, usually, no. It is one of these multicausal
things that result from working with ecologies. Almost everything in an
ecosystem is connected. Suppose the climate changes so that an organism in
question has the options of moving or dieing. It may not be able to move because
it requires a specific habitat that simply isn't available near it. Take the
koala. It feeds on eucalyptus trees. If the climate changes and it has to move,
it will simply die because the trees it feeds on are not that common. Even if
there are other places it can move to, there needs to be some way for it to get
there. If the next forest of trees is a thousand miles away, the population is
SOL (sh~ outta luck for those of you who haven't seen this expression). Ok, this
is a bit simplistic and people may quibble with the exact example, but the
meaning still stands.
Now, even assuming that there is a way for the animal to migrate so that there
is unbroken habitat or patches close enough together that it can traverse the
intervening areas, that still does not mean it will be successfull. There will
most likely be other animals in those areas that are already occupying those
niches which will be reluctant to leave or share. That means the organism in
question will have to battle an already entrenched species and so will probably
lose. Yes, there are plenty of examples in which an invading organism wins and
takes over, but in those cases there are other factors at work and in the vast
majority of cases, the displaced organism simply can't compete with the native
organisms and if it lives, lives on the fringes.
And suppose it can overcome all of these things, it will be exposed to pathogens
and predators it is unaccustomed to and will have to learn to deal with which
kills most of them.
So there you have it, in a very simplistic form ad only mentioning a few
factors. The upshot is that organisms are tied to their environments and most
can not easily just pick up and move when the weather turns bad. Some can, yes,
but most don't succeed.
The time frame will lessen some of these problems, but will not eliminate any,
nor will it do anything about some of them, and it all depends (an ecologist's
favorite word) on the specific situation which problems are lessened and which
ones are not affected.
Sorry for the incompleteness of the answer, but I am at work which doesn't like
me doing this on company time and I keep getting interrupted so my train of
thought is being constantly derailed. What I suffer for my hobbies.