Hurricane Katrina — a very big storm by any measure — has now
been called the “largest ecological disaster in U.S. history,”
according to the Christian Science Monitor, because it
“killed or damaged about 320 million trees.” Moreover, Katrina was
a double ecological whammy, as the downed trees will eventually rot
or burn, releasing another increment (probably too small to detect)
of dreaded carbon dioxide, the main global warming gas. The
Monitor’s report was based upon an analysis of satellite
imagery conducted by scientists at the University of New
Hampshire.
Wait a minute. Hurricanes have been a fact of life for the
forests of southeastern North America ever since there were
forests, and that’s a pretty long time.
The natural vegetation of the coastal southeast consists largely
of a mixture of Pine and Oak species. That’s not what it is today,
because today’s vegetation isn’t natural. Rather, it’s virtually
all a commercial mix of softwoods designed to grow fast and tall,
so the trees can quickly be sawed into houses. Today’s forest
probably maintains a higher vertical profile than the one that was
here before, and it’s also largely protected from fire, but not
from hurricanes.
Back before us, believe it or not, weather was pretty much the
same as it is now. Consider the very severe drought currently
plaguing the Deep South. Remember those forest fires in Georgia
late last summer? The only reason they didn’t burn down most of the
state’s forests was that they were unnaturally extinguished.
It’s fair to say that the integrated intensity of the
southeastern drought may be a one-in-fifty year occurrence. That
would mean, in a “natural” world (i.e., one without human sprawl) a
southeastern forest would go about fifty years before
combusting.
Or, perhaps, taken down by a hurricane. Pines and oaks have been
around about 100 million years. Hurricanes have been around
longer.
Here’s the cool part: the present era. Ninety-five percent of
the last 100 million years were warmer than now. It’s only about 5
million years or so ago that we began to slip into the current
ice-age climate (from which carbon dioxide may mercifully extricate
us, some say).
Now, just for fun, let’s assume that Katrina was a product of
global warming. Forget that no scientist will stand up and point
the causative finger. But, if it was, Katrina was therefore typical
of many hurricanes of the last 100 million years. In other words,
the natural southern forest evolved in a world studded with
Katrinas.
Part of the modern climate mythology is the assumption that
every significant climate burp, such as the big El Nino of 1998, or
the big hurricane season of 2005 is portentous of ecological
disaster. Hardly. In fact, if today’s species were not adapted to
these extremes, they simply wouldn’t be here.
It’s almost too bad that we don’t have the “natural” forest of
southeastern North America anymore. I’ll bet, if we did, that some
ecological researcher would have discovered indeed that such a
forest in fact requires hurricanes, just as the flowering
plants of the desert southwest require El Nino rains for
germination and subsequent reproduction.
There once was a concept of “potential natural vegetation” of
the United States, which was thought to be what would eventually
appear in the absence of human management. The modern view of
forest dynamics is somewhat different, but, nonetheless, the
“natural” distribution of the oak-pine forest pretty much
corresponds to the inland reach of the strongest hurricanes.
OK, that was my original Ph.D. topic proposal, back in a 1971
paper at the University of Chicago. It was laughed at, because, at
the time, ecologists didn’t think weather or climate were very
important modulators of ecosystem behavior. Four years later, the
surface temperature of the planet began to rise. About a third of a
century later, a hurricane was blamed for the largest ecological
disaster in our history.
Now it’s the other way around. Weather and climate are now
assumed to be driving the world into ecological chaos. It seems
reasonable that, say, 30 years from now, something else will be to
blame.
Finally, whenever a hurricane (or a fire) takes down a forest,
it’s not replaced by anything but another forest. That vegetation
will absorb some of the carbon dioxide that Katrina’s trees left
behind. It will eventually look a lot like the one that got blown
down, only to await the sawmill, or the next big hurricane.
Patrick J. Michaels is senior fellow in environmental
studies at the Cato
Institute and author of Meltdown: The Predictable
Distortion of Global Warming by Scientists, Politicians, and the
Media.
