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Weed raising anxieties along Colorado River

Dennis Webb/Special to the Daily

When wildlife lovers look along the Colorado River near Silt, they see towering cottonwood trees housing nests from which herons survey their domain.

It’s a threatened domain, however, under attack by an invader that is drawing increasing attention from local to federal governments.

The tamarisk, a water-loving plant imported from Eurasia, has been gradually taking over riverbanks since its introduction to the Colorado Plateau early in the 20th Century. Recognized for years as a scourge of river ecosystems, the thirsty tamarisk is now a prime target for eradication due to the recent drought.



Steve Anthony, vegetation manager for Garfield County, can list any number of reasons for more aggressively eradicating the woody, shrub-like tamarisk plant.

Even with the focus on water waste, tamarisk invasion into cottonwood habitat, home to herons and eagles, remains a pressing concern for Anthony.

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“It’s been documented that we’re losing that. That’s being displaced. Nowhere is that more evident than between Silt and Rifle,” he said.

Forests of tamarisk, accompanied by another invasive species, the Russian olive tree, are taking over as old cottonwoods are dying.

“We’re not seeing the new cottonwoods coming in,” Anthony said.



Mistreating the natives

The tamarisk was introduced as an ornamental plant and also to control erosion. Like many invasive species, it fared far better than expected.

Its extensive root system enables it to thrive even during drought, at the expense of nearby native plants that it crowds out.

Also known as salt cedar, tamarisk increases soil salinity, making it harder for neighboring plants to survive and adding to the problem of salt in the Colorado River.

It also increases fire danger along rivers, yet can’t be killed by burning.

Tamarisk reproduces rapidly, according to a tamarisk fact sheet on the state of Colorado’s Web site. A mature tamarisk shrub can produce 250 million seeds per year. The small seeds are easily dispersed by Colorado’s winds and streams, and germinate in just 24 hours. Within a few weeks, the tap root penetrates deep into the soil or sand.

Tamarisk leaves contain little nutrition for wildlife, and the plant harms animals by eliminating the native vegetation they rely on for food and shelter.

The tamarisk also steals a precious commodity. One large tamarisk can use as much water in a single day as a family of four. Anthony said a typical young tamarisk can consume 200 to 300 gallons per day.

“If you have an acre of tamarisk, you can imagine the math involved here. It’s pretty significant,” he said.

Funding for research

U.S. Rep. Scott McInnis, R-Grand Junction, did the math.

Then the longtime advocate for Western Slope water introduced a bill early this year to allocate $1 million for Mesa State College to conduct tamarisk research. The college also would provide technical and education assistance to governments and individuals working to control tamarisk.

A U.S. Senate bill introduced by Sen. Ben Nighthorse Campbell, R-Colo., goes even further. It would allocate $20 million, earmarking 90 percent for eradication and habitat rehabilitation.

In his bill, Campbell states that tamarisk occupies between 1 million and 1.5 million acres in the West, and uses 2 million to 4.5 million acre feet of water per year. An acre foot is 325,851 gallons.

The water used by tamarisk stands in the West could provide for 20 million people or the irrigation of more than 1 million acres, he contends.

Colorado Gov. Bill Owens has also jumped into the tamarisk battle. He ordered the state departments of Natural Resources and Agriculture to work with other cooperating state, federal and local agencies, with the goal of eradicating tamarisk on public lands in 10 years.

Owens gave the Department of Natural Resources a year to outline a plan for achieving this goal.

Anthony said the biggest need is for funding to carry out the job. General weed control can cost $100 an acre, said Anthony. The cost of eradicating the pesky tamarisk can cost up to $2,000 an acre when workers use chain saws to cut it down.

Anthony is chasing down tamarisk control in other spots, including lands in Glenwood Canyon held by the Colorado Department of Transportation. He’s also worked with Eagle County along the bike path near Bair Ranch and with the U.S. Department of Energy at the former uranium ore processing site west of Rifle.

It’s all a good start, Anthony said, but he looks at the control of weeds such as tamarisk as a long term job.

“You’ve got to get started on something and keep plugging away on it,” he said.

Tamarisk Symposium

– Oct. 22-24 in Grand Junction

– Two days of experts speaking on issues related to tamarisk control

– Field trip to Walter Walker Wildlife Refuge

– $100 conference fee, registration deadline Oct. 8

– Information: (970) 244-1834, or http://www.coopext.colostate.edu/TRA/tamarisksymposium2003.html


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