Colorado River: A Changed View

Tamarisk Fuels Reduction and Watershed Restoration

Moab Field Office

Brown tamarisk trees showing the effects of beetle killIf you are a long-time visitor to the Moab area and have camped along the Colorado River or one of its tributaries, your next stopover at one of our campgrounds may be a bit of a surprise!

Over the past fifty years thick, woody invasive plants spread along the riverbanks and literally surrounded BLM campsites.  Although the trees themselves had become commonplace to visitors as well as locals, the increasing possibility for a fire event along the river required corrective action.

Tamarisk (background) displaces native species such as willow (foreground)

Over the years, the BLM Moab Fire District focused on removing the invasive species tamarisk ( Tamarix parviflora ), Russian olive ( Elaeagnus angustifolia ), and other noxious weeds at points along the riverway and around the BLM campgrounds.  These fuel reduction activities included hand cutting and mechanical cutting followed by herbicide treatment and burning.  However, beginning in 2006 a relatively new form of biological control—the tamarisk beetle—has been hard at work devouring the tamarisk.  The tamarisk leaf beetle ( Diorhabda elongata) was introduced along the Colorado riverway near Moab by the state of Utah in connection with Grand County, and by 2007 the evidence was clear that the beetle was making headway.  Large stretches of tamarisk began to turn brown and brittle and by the end of summer very little tamarisk in the Moab Field Office area remained untouched by the beetle.

Bullhog treatment in tamariskWhile the tamarisk is able to withstand a few seasons of beetle defoliation by producing new leaves from root reserves, it is expected that the trees will eventually succumb to repeated defoliation.  In response, the BLM, in collaboration with the Utah Partners for Conservation and Development and other entities have intensified efforts to reduce the number of existing invasives before the fire hazard is multiplied by dead and dying tamarisk.

Some may miss the greenery and shade the invasive species have provided over the years, although tamarisk and Russian olive are aggressively displacing native species such as cottonwood and willow.  Once established, tamarisk can survive without access to groundwater and can consume large quantities of soil moisture, inhibiting or preventing the growth of native plant species.  If you’ve ever camped under the shade of cottonwoods, you realize how much they would be missed!  Thin and pile treatment, Onion Creek

Contracted fuel reduction crews arrived last fall to manually cut and pile the trees in seventeen different units covering a total of approximately 85 acres. In January, BLM fire crews began the arduous process of burning each of the hundreds of piles that were stacked by the contracted crews.  Seven additional units were specifically chosen to be treated by a contracted “bullhog,” a mechanical device that cuts, chips, and shreds large trees. 

Fremont cottonwood in recently treated area near Dewey BridgeOver one hundred acres were treated mechanically in several areas including Roberts Bottom and around Dewey Bridge.  Some of these treated areas present a stark contrast to the dense thickets of invasives that had been there for so many years, but one can almost imagine the native cottonwoods and willows that could thrive in the absence of the invasives.

Invasive plant reduction activities along the waterways are expected to continue for many years and some areas may require multiple treatments.  The BLM is working closely with the Utah Division of Wildlife Resources, the U.S. Fish and Wildlife Service, Grand County, and the Southeastern Utah Tamarisk Partnership (SEUTP) to identify areas that may need re-treating and/or additional acreage for treatment.  In addition, many areas will be targeted for seeding and the planting of seedlings to help achieve a return to a healthy native riparian ecosystem.

If you are interested in learning more about this significant effort, here are links to several informative websites: