Do you know or like Tamarisk (Salt-cedar) trees along your favorite riparian birding sites? I would wager that you have an intense dislike for them. I have a different perspective to share with you.
During the early 1970s I led a three-year study of small mammal communities along the Colorado River in the Grand Canyon. It was a live-trap mark and recapture study in both the new riparian (Tamarisk) beaches and the old Mesquite) pre-dam beaches. What I found was striking and it has colored my personal view of Tamarisk status in the Southwest. To put it simply, I found that the composition of the small mammal communities in the Tamarisk areas was far more diverse (therefore stable) and far more dense than it was on the old Mesquite strips along the River. What this means to a community Biologist – no emotion here – is that these new Tamarisk areas are biologically rich and should not be removed without some serious planning and thought.
Why should these areas be so rich?
• Tamarisk habitats are very dense and small mammals (many other groups also) will always favor dense environments because it gives them a sense of security. Ecologists call this positive thigmotaxis. You call it snuggling under the covers on a cold night.
• It is cooler (shadier) under the dense trees.
• The humidity is higher there – that matters in the arid Southwest.
• The geometry of the habitat is very complex which opens up more niches for a greater diversity of animal species including insects.
During the late 80s a program of Tamarisk extermination was begun with the introduction of a Chinese beetle, Tamarisk Beetle, which will devour Tamarisk (only). Eventually, this beetle will denude a Tamarisk area and leave behind it dead trees and naked land. The program works exceedingly well as far as the mere removal of the trees is concerned. However, tree removal should not be the ultimate goal; the focus should be on habitat integrity. Thankfully, there is a movement now to replant these areas with native will species which will provide a fair measure of the same communal benefits that Tamarisk delivers now. And, so, over time and with the application of huge amounts of money, much of our riparian land can be restored. From the viewpoint of a community Biologist such as myself, one wonders what is the point of all this.
Please understand that I hate the Tamarisk and I deeply regret the fact that it was introduced and has spread so quickly. From a purely emotional view point, these invaders need to go tree heaven. However, they are here and we will never completely rid ourselves of them. True, there are lots of Tamarisk Beetles in China. Why is that? The reason is that there are lots of Tamarisk trees there also. Clearly equilibrium was reached a long time ago. Oh, and no money was spent to reach it. My position is: keep replanting as we go – within reason – and simply accept Tamarisk as part of our “new” native riparian systems. If you want a boarder perspective, ask ‘Ol Chuck Darwin. Or, look into the fossil record; there was a time when Homo sapiens was a new invasive species, too.
One final point: it turns out that some species actually thrive in Tamarisk thickets; the thicker and wetter the better. Some are even near and dear to our hearts. One is called the Willow Flycatcher. Remove the Tamarisk habitat and you seriously threaten this little Rare and Endangered bird.
Ah… what to do? Well, what would you do if you saw a rare and endangered raptor aiming at a rare and endangered mouse?
Oh, one more thing: the beetles were introduced in Colorado are heading South. Perhaps they will hit the Verde in a year or two?