On Tue, 13 Feb 1996, Kathleen Hunt wrote:
> Isn't 12 millenia awfully short for the evolution of an entire
> ecosystem? My understanding is that North American grasslands and their
> associated fauna evolved together over the past 2 *million* years, and
> that the ungulate extinctions that happened 12,000 years ago were,
> evolutionarily speaking, a very recent aberration.

As for the Columbia Basin (the ecosystem I discussed), you could argue
strongly that it really *did* evolve in only 12 milennia because it was
entirely under water (yes, all of lowland eastern Washington was under
water) for brief periods during the last glaciation (due to fluctuations
of the ice dam that held Lake Missoula). Water from melting glaciers also
flooded and carved the Okanogan and Methow Valleys. The fast flooding and
receding of waters in the Columbia Basin 12,000 years ago must have eroded
and killed all of the vegetation in the region, perhaps only leaving
floating seeds to reestablish themselves. The Channeled Scablands remain
barren in some areas to this day because of the massive floods removing
soil. After the floods, I doubt much was left of the 'old' ecosystem.
Just soil, water, and some seeds and dead material. Time to evolve a new
one!

Overall, if you actually refer to the ecosystem evolving as a unit, I
would concede that you're right. I think this ends up being a matter of
trying to put a dynamic thing into some sort of static category (when in
the past did this ecosystem come to what we consider it's natural state?).
So I think it's a matter of semantics. Anyway, whether or not 12,000
years is enough to evolve an ecosystem would depend on how you define that
ecosystem. Regardless of any of that, the vegetation in any ecosystem
will certainly grow and change (evolve??) over 12 milennia.

Sorry to hear about the Merlin death. They are a favorite winter bird of
mine. I used to live in the Madrona area, and there was a large
dead-topped redwood on the top of the hill. Every afternoon in winter, a
Merlin would stop in between 4:45 and 5:15. It was very punctual. I
found a Sharp-shinned Hawk on the lawn last year in the same condition -
head was just mush.

-------------
Michael R. Smith
Univ. of Washington, Seattle
whimbrel at u.washington.edu
http://salmo.cqs.washington.edu/~wagap/mike.html