Species versus species

The fight against tamarisk trees that have invaded much of the Southwest suffered a major setback recently when the U.S. Fish and Wildlife Service announced it was abandoning its program of releasing saltcedar leaf beetles to eat the tamarisk.

As The Daily Sentinel’s Dave Buchanan reported last week, the decision came in response to a lawsuit filed by environmental groups. That lawsuit was aimed at protecting the endangered southwestern willow flycatcher, a small bird that has come to make tamarisk its home.

The good news for this area is that the Southwestern willow flycatcher doesn’t breed and nest along this part of the Colorado River and its tributaries. As a result, state officials and the Tamarisk Coalition can continue releasing the saltcedar-devouring beetles in western Colorado. People can view the successful results of that ongoing effort in the acres of brown and dying tamarisk along much of the Colorado River corridor through the Grand Valley and into eastern Utah.

However, the Fish and Wildlife Service decision will have significant impacts in places like New Mexico, Arizona, southern Utah and southern Nevada, which have their own battles with tamarisk as they try to restore river corridors to their native plant species. The Four Corners region of Colorado may also be affected.

Worse, the decision pits the Southwestern willow flycatcher against other species in the Southwest that would benefit immensely if the tamarisk were eliminated or significantly reduced.

Tamarisk is known to soak up massive quantities of water from the Colorado River Basin. Some estimates have put the figure at one million acre-feet of water annually. That means roughly the equivalent of the water in Blue Mesa Reservoir — Colorado’s largest lake — is being sucked out of the river basin each year by tamarisk.

It’s true that native plants — particularly cottonwoods and willows — would also take large amounts of water from the basin if the tamarisk were gone. But there are differences.

For one thing, their root systems don’t go as deep as tamarisk’s and, as a result, these plants are less likely to be found on benches or small drainages well-removed from a river corridor.

More importantly, the cottonwoods, willows and other native plants provide a welcoming habitat — lots of shade and ample ground cover — for all manner of wildlife. Tamarisk exudes salt into the soil, leaving the ground beneath each plant virtually devoid of cover. And its leaves offer little shade.

Southwestern willow flycatchers may find tamarisk stands a decent home, but few other species do.

The flycatchers, of course, once lived in native plants, before the Asian tamarisk plants spread in the Southwest. And they would again, if the willows and other plants were restored. But there are fears that the birds wouldn’t survive in the period between the elimination of the tamarisk and the restoration of native plants.

Still, it’s too bad the Fish and Wildlife Service and the environmental groups that sued decided it was best to halt the use of the best weapon we’ve seen in the fight against tamarisk to protect one wildlife species at the expense of most others.


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