Stuart wrote: "I think there are a few major surprises for scientists as
the world starts to warm up. Personally I think that species will be able
to deal with it - since they have undoubtedly been through it all before -
however the rate of change will take a pretty significant toll, though I
doubt it will lead to lots of extinctions that some people predict - ever
the optimist."

Global warming (which I believe has begun) is likely to produce more than a
warming of the atmosphere and amelioration of the climate at higher
latitudes. Severe storms are likely to increase in frequency and severity
as heat is pumped into the surface of the oceans and the lower atmosphere.
Thus for pelagic species, bird wrecks and dispersion of species out of
their current range could increase. The overall productivity of the oceans
may increase as a result of more vigorous upwelling and planktonic species
composition may change due to increased nutrients and warmer water; not
necessarily a good thing. (One predator species may be favored over another
by prey size: copepods vs euphausids, for example.) Sea level rise can
profoundly affect both nesting and feeding areas adjacent to tidelands.
(Bear in mind that there are confounding variables, such as the increase in
atmospheric pollutant haze, that our climate models handle poorly or not at
all, so we're still in the realm of speculation)

On land, the higher latitudes may experience warming but plants can extend
or change their range only as a function of seed dispersal and competition
with the pre-existing flora. Thus, we could see a latitudinal compression
of some biomes as the southern limits of some species are pushed rapidly
poleward but the northern limits expand slowly. Coupled with current
habitat loss we could see smaller population of many species, making them
more vulnerable to other factors. However, simple movement of biomes
poleward is impeded (stopped?) when the available substrate is unsuitable:
the Precambrian Shield is not likely to be hospitable to mesic forest tree
species and the Southern Ocean is a rather formidable barrier, not to
mention what's on the other side of it. Any changes in the heat balance
will also affect rainfall patterns. Species with a tendency to vagrancy
are obviously pioneers ready to occupy new, inviting habitat. Of course
we're seeing range expansions and contractions now; many ascribable to
human influences. Gene suggests that vagrancy may not be an adaptation,
just an inability to find one's car in the parking lot. But a tendency in
a species could be adaptive.

Stuart says that species will deal with this "since they have undoubtedly
been through it all before." But, as he points out, the *rate of change*
is important. I suspect we're dealing with something at least as dramatic
as the relatively recent Little Ice Age or the Climatic Amelioration of a
thousand years ago, but on a longer time scale. These latter climate
changes are normally occurring, little perturbations within the current
interglacial period. We're adding more amplitude to the signal, but not
necessarily in only one direction. Hang on, the ride might get a little
bumpy. (However, this year's weather is still part of the noise, not the
signal.)

Herb Curl - powered by Caffeine


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