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Eagle River Watershed Council: A voracious invader

Melanie Smith
The Current
Eagle River Watershed Council, with collaboration and support from the Bureau of Land Management, Eagle County’s Open Space and Vegetation Management departments, sawyers from Old Growth Tree Service and the Western Colorado Conservation Corp’s Women’s Fire Crew and volunteers from the local community recently undertook a two-day tamarisk mitigation effort in Dotsero. | Courtesy photo

Visualize a bathtub full of water, then multiply it by six. 

That’s about 200 gallons of water, and it’s what a fully-grown tamarisk shrub can consume in a day.  What is tamarisk, and why is it such a threat?

Melanie Smith
MelanieSmith

Tamarisk, also known as salt cedar, is an ornamental shrub. It was imported to the United States in the late 1800s, mainly in an effort to reduce erosion, stabilize railways and provide windbreaks. Since then, the plant has spread voraciously throughout the Southwest.



With its delicate pink blossoms that drip from its feathery leaves and branches each spring, the tamarisk’s appearance is quite lovely. But underneath that innocent exterior lies a monster.

Several characteristics of the plant make it a destructive force, especially threatening to streambeds, waterways and riparian areas in already drought-ridden regions. Tamarisk is an extremely stubborn and deeply rooted invasive plant that colonizes swiftly with its dense vegetation. This can constrict the river, changing flow patterns and creating shallower waterways.



Native species that rely on deeper, cooler channels and sediment-free streambeds to rest, feed and reproduce don’t thrive in shallower waterways and may become displaced. Another impact of this shallowing is that flooding can occur during periods of runoff, due to the changed hydrology.

As mentioned above, tamarisk plants are thirsty, drinking around the same amount of water per plant as a mature cottonwood tree. The cottonwood, however, offers more nutritious grazing for livestock and wildlife, does not grow as densely or chokingly, and provides more cooling shade to the river. Tamarisk grows thickly and its woody trunks and branches can lead to increased intensity of wildfires that may spread through an infested area.

As if that’s not enough, tamarisk has the ability to change soil chemistry, which can reduce biodiversity and prevent the growth of native vegetation.



Where is tamarisk found?

The plant can be found all across the western states, from California through Arizona, Nevada, Utah and Colorado, and the warming climate and continued drought conditions are adding to its possible range.

Here in Eagle County, tamarisk is currently only found in far western portions, mostly in the Dotsero area along the Colorado River. However, with warmer, drier climate patterns, it is plausible that tamarisk may spread up the Eagle River and other tributaries in Eagle County. With 40 million people dependent upon the limited quantities of water in the Colorado River, no threat to this water should be ignored.

What is being done?

Fortunately, there are actions that can be taken to mitigate the spread of this noxious plant. From the use of the tamarisk beetle, a natural enemy of the tamarisk plant, to mechanical and chemical means, control methods do exist. However, mitigation efforts are typically most effective when they combine multiple methods and are frequently costly and physically intensive for workers and volunteers. Additionally, sites must be monitored and frequently require repeat treatments for multiple years to see lasting success.

Eagle River Watershed Council, with collaboration and support from the Bureau of Land Management, Eagle County’s Open Space and Vegetation Management departments, sawyers from Old Growth Tree Service and the Western Colorado Conservation Corp’s Women’s Fire Crew and volunteers from the local community recently undertook a two-day tamarisk mitigation effort in Dotsero.

The project, which began in May 2021 and has multiple phases, has so far resulted in the mitigation of more than four acres of tamarisk.

As a rookie participant in the effort this spring, I was excited to join the crew and experience the project firsthand. Each of the two mornings of the project, we rafted to the site with boats containing chainsaws, herbicide and applicators, personal protective equipment, loppers and 25 workers. After a safety talk and instructions, we set out in groups to tackle the tamarisk.

Some workers trimmed sprouts that had emerged since last year’s effort and treated each with an herbicide to kill the plant without harming other plants, wildlife or the water. Some carried brush and slash from the sawyers up ahead, and some quickly moved in to the fresh-cut stumps to apply herbicide.

It was a great project — tiring and rewarding, and one of the many planned in our region to continue combating the plant. To learn more about tamarisk and what action can be taken to control its spread, check out the resources below.

If you have tamarisk or other noxious weeds on your property or in your neighborhood and you are interested in resources to remove them, please check out the Weed Warriors program, a joint program with Eagle River Watershed Council, Eagle County Vegetation Management, Eagle Valley Land Trust and the Land and Rivers Fund.

Melanie Smith is the development and communications Manager at Eagle River Watershed Council. The Watershed Council has a mission to advocate for the health of the Upper Colorado and Eagle River basins through research, education and projects. Contact the Watershed Council at 970-827-5406 or visit ERWC.org.


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