The War Against Tamarisk...Have We Finally Won?
...and an unexpected and unpredictable side effect...the rise of the willows
By Jim Stiles
I
have had a long and peculiar relationship with tamarisk ever since it
was introduced to me, decades ago, when I first landed in canyon
country. Of course tamarisk was itself introduced to the American
Southwest many years earlier, to control bank erosion along California
canals and waterways.
I
have no particular fondness for the exotic plant and, in fact, it is
the only living entity besides a human being that I have ever actually
tried to punch (I had become so entangled and trapped in a dense tammy
thicket on a particularly hot summer day, that I truly believed the
plant was holding me against my will and I took a swing at it!)
It
is reported that tamarisk has infested almost 1.6 million acres of
riparian habitat in the Southwest. It consumes massive amounts of
precious water and is said to have a "devastating impact on watershed
biodiversity and ecosystem health."
Still,
the damn weed is there....it's everywhere, and until very recently, all
the millions of hours of labor and barrels of toxic poisons and the
expenditures of millions and millions of dollars to "control" the
plant struck me as absurd.
Many
years ago, I waged a long and gruesome battle with my old employers at
Arches National Park over a plan to burn and poison tamarisk at the
lower end of Salt Valley. The tamarisk was very old and had, in fact,
stabilized the wash enough that other native vegetation could take
hold. And deep in the shadows of the densest of the tamarisk thickets
was a waterhole which provided a perennial drinking spot for the
native wildlife. Ultimately I lost the battle to defend the tammies and
the waterhole as well...Last time I checked, it was gone.
(Thanks
to the internet and The Zephyr web site, you can read that long tale in
its entirety without me being redundant. Just click here to read my
story of the Secret Spring in the Aug/Sep 2004 issue).
But
a few years ago, scientists thought they may have found a way to
eradicate the tamarisk biologically, without poisons and all that labor
intensive cutting and burning. If it worked, what it meant was that all
those years of battling the tamarisk with herbicides and chain saws had
not only been an utter waste of time and money, but ultimately even
counterproductive.
Still,
we can only look ahead—an organization called the Tamarisk Coalition
has taken a leadership role in monitoring and evaluating this latest
development. According to the Coalition:
But
a few years ago, scientists thought they may have found a way to
eradicate the tamarisk biologically, without poisons and all that labor
intensive cutting and burning. If it worked, what it meant was that all
those years of battling the tamarisk with herbicides and chain saws had
not only been an utter waste of time and money, but ultimately even
counterproductive.
The
primary objective of our project is to monitor a biological control
called the tamarisk leaf beetle. Biological control, or bio-control,
uses specific organisms to control an undesirable organism, in this
case tamarisk. The tamarisk leaf beetle works to control tamarisk by
repeatedly defoliating the plant over several years, stressing it to
the point of death. The Colorado Department of Agriculture's Palisade
Insectary released the bio-control in 2005, after several years of
intense collaborative research by many different agencies and
universities. As a result, the tamarisk beetles have defoliated trees
along hundreds of river miles. This is now one of the most dramatic
cases of biological control in history with the potential to alter
ecosystem processes on a scale that spans three states and thousands of
river miles.
And
it appears the little tamarisk chomping beetles have been successful
beyond all expectations. Since I spend most of my time away from Moab
these days, I had not taken a drive along the river road in almost a
year. Even in August 2008, it was evident that the beetles were
effectively killing off the tamarisk. Along miles and miles of the
Colorado Paver, the tammies had turned brown and looked as if they were
on their way to an early demise, which is precisely what everyone was
hoping for.
But
a few weeks ago, I revisited the river for the first time in almost a
year and I was shocked by what I saw. In just a year, the beetle
infestation had weakened the tamarisk so severely, that not only was it
dying off more rapidly than I had ever anticipated, but a lush fringe
of willow trees, a native plant, was already establishing a beautiful
silver-green fringe of foliage along the Colorado River. I was
delighted. And then I thought about the transformation a bit. My
recollection of old photographs
of
the Colorado River, along the main channel at least, was that much of
the shoreline was free of any heavy vegetation, including willows. The
willow has a very shallow root system that tends to spread
horizontally, but not deeply into the river-bank. The tamarisk, on the
other hand, is notorious for its deep tap roots. Not only was it able
to suck water from deep below the surface, it was downright impossible
to uproot the cursed plant. It's why the tamarisk was, in most cases,
able to withstand the great floods of 1983 and 1984. While the
highwater—it approached 150,000 cfs in Cataract Canyon—practically
took out Glen Canyon dam, the tammies barely took notice.
Now,
with a new native plant species taking hold in vast numbers, sometimes
in places it could never get a foothold before, what would happen if
the river was hit with another great flood? Would the shallow rooted
willow be able to withstand the high fast flowing river? Nobody is sure.
Tim
Carlson, Research and Policy Director for the Tamarisk Coalition,
believes many of the newly established willows may indeed be uprooted
by a major flood, though he notes that flooding isn't nearly as
frequent as it once was, before the era of dams and controlled river
flow releases. But they can happen, even now.! 983 is proof of that.
Could a hundred year flood send millions of willows down the Colorado
River into the upper end of Lake Powell? Carlson even thinks that might
be a benefit to the lake since an influx of organic material may
provide needed nutrients to a reservoir that grows more dead and
stagnant each year. But that's a lot of "nutrients" arriving all at
once. Try to picture the reservoir around Hite for moment after such an
exodus of willow trees. ..the mind boggles.
Still the prospect of navigating a river with a million uprooted willow trees may be a
daunting
task for the boatman of the future. Ultimately, no matter how
diligently we try to fix the man-caused errors of the past, we always
seem to create new ones.
I
wonder what would happen if we could just leave Nature alone for a
century or two and let her try to sort things out on her own...somehow
I doubt we'll ever know.
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