It’s a given here in the desert southwest that tamarisk, a tough little red-barked tree that grows along our river banks, is evil. A European immigrant that arrived more than a century ago, it now dominates the banks of our desert streams and rivers, choking out native cottonwoods and sucking up precious water. At least that’s the conventional wisdom.
(tamarisk along the Colorado River in Grand Junction, image courtesy Colorado State University)
Here in Albuquerque, we’re spending big bucks to clear it out of our bosque, the woods along the river, based on that conventional wisdom. I’ve been pretty enthusiastic about the results – beautiful open woods, with the cottonwood returned to its regal riverside dominance. But I keep hearing inklings from the science community that we know less about the tamarisk and its role here than we think.
The latest inkling comes from the March-April issue of Southwest Hydrology, a publication out of the University of Arizona.
The article is based on a conference last fall in Grand Junction – the 2005 Tamarisk Symposium – that brought together researchers grappling with the tamarisk issue.
The conventional wisdom, as outlined by USGS plant ecologist Pat Shafroth, is that tamarisk pushes out native vegetation, sucks up more water than the natives, carries fire more easily and is better adapted to the results of fire. The conventional wisdom also suggests that if you simply root it out, natives will sweep in to replace it.
But there’s another side to this story – the suggestion that tamarisk’s spread is simply a response to the way we’ve changed the river systems with dams and other flow regulation. In other words, there is no natural riparian system left, and the salinity, increased fire etc. that we’ve been blaming on the tamarisk is actually a result of the changed hydrology.
It seems clear that the real story is some mix of the two views, with tamarisk not a benign player, but not the cause of all the evils for which it’s blamed. The trick is to sort things out a bit better so we don’t have unrealistic expectations about the benefits to be hand by the eradication efforts now underway.