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Re: _Night Comes to the Cretaceous_



In a message dated 98-08-08 07:18:53 EDT, jwoolf@erinet.com writes:

<< There is nothing all that strange about a mass extinction, if you
understand
 ecological dynamics.  It's entirely possible for one element to get out of
 alignment and have a massive destabilizing effect.  An unstable ecosystem is
a
 vulnerable ecosystem, and it can fall apart in a shockingly short amount of
 time.>>

You're still talking about local effects here. The world comprises hundreds or
thousands of ecosystems.

<<If something wipes out the top predator, for example, unpreyed herbivores
 can strip the land bare and eat themselves into starvation.>>

How would the disappearance of, say, _Tyrannosaurus rex_ in North America
affect the herbivorous dinosaurs of, say, India?

<<  Or if a new type of plant appears which spreads rapidly and which none of
the big herbivores can eat -- kudzu or spurge, for example. Or a fungus or
microbe that parasitizes a large array of species like _Pfiesteria_, the
infamous "cell from hell" that has been ravaging the fish populations along
several parts of the East Coast every year for several years now. >>

How would the appearance of kudzu in, say, South Carolina, cause the
extinction of, say, bald eagles in Alaska? Kudzu arrived from somewhere else;
why isn't the place it arrived from devastated?

Global mass extinctions >must< have global causes.

<<Maybe the impact hypothesis is right.  It's attractive, it explains the
direct physical evidence, and it certainly satisfies the human desire for big
spectacular phenomena having big spectacular causes.  But it doesn't explain
all
the evidence, and past experience shows that neat and simple explanations for
ecological breakdowns are more often wrong than right.>>

I certainly don't care how spectacular the asteroid/comet impact might have
been (I wasn't there to see it, lucky for me), and I have absolutely no desire
to give the extinction of the dinosaurs a big spectacular cause if it in fact
did not! And--which "evidence" does the asteroid/comet impact at the K-T
boundary not "explain"? If you do indeed have evidence that the impact
>didn't< cause the K-T mass extinction, trot it out. Maybe it's publishable.