Tamarisk, the Infamous Weed of the West

Budget Dumpster
January 5th, 2016
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You’ve probably never given much thought to the kinds of plants that grow in your local park, or in your own backyard for that matter. As long as the garden isn’t ensnared in weeds and the kids aren’t coming home with poison ivy every weekend, what is there to worry about?
According to the US Fish & Wildlife Service, there is plenty to worry about. The FWS estimates that North America is home to more than 4,300 invasive species of plants and animals, meaning that they are capable of negatively impacting the economy, environment, and even public health. One of the most infamous examples is the zebra mussel, a mollusk native to the waterways of Eastern Europe that was unwittingly transported to the Great Lakes via shipping vessels. Since its introduction it has killed tens of thousands of native birds through botulism, endangered several species of native mussels, and caused $250-500 million worth of damage to municipal water supplies and hydroelectric plants.
That’s some serious damage for something the size of a fingernail.
The Invaders are Coming
Obviously, identifying and containing these species is an important job, but it’s one that often falls on the shoulders of local and state agencies, institutions that aren’t exactly bursting with resources. Fortunately, there are many non-profit organizations out there keeping their eyes on the sky, and the soil, for signs of the creeping advance of invasive species.
The Tamarisk Coalition, TC for short, is just one example of the kinds of organizations that devote themselves to countering the worst that these species have to offer. Based out of western Colorado, the Tamarisk Coalition has been working to restore the rivers of the West since 2002. Their name comes from one of their primary targets, an invasive species of shrub known as tamarisk (Tamarix spp.) or “salt cedar”.
The plant itself looks rather innocuous at first glance, with pinkish-red flowers and feathery leaves. In fact, it was first imported to the US as an ornamental for its decorative qualities, as well as a way to control erosion due to its fibrous roots. The latter proved to be a major problem for other plants that like to grow along riverbanks.
As soon as tamarisk spreads to a new area it can quickly dominate the shoreline thanks to its extensive root system which can grow to an impressive length of 100 feet. In the most heavily affected areas this makes it almost impossible to use rivers for recreation as boaters and others can’t traverse through the dense thickets it creates. On top of this, tamarisk tends to accumulate in dry, woody stands, raising the risk of wildfires in areas that aren’t adapted to those kinds of blazes.
If You Can’t Beat Them, Join Them
TC focuses on holistic riparian restoration, rather than simply uprooting as many invasive plants as possible. Since many invasive species have essentially become a permanent fixture of their new ecosystems, TC’s goal is to control invasive species to a level that they are not ecologically, socially, or economically damaging.
That is the essential principle behind the group’s main activities, including its educational outreach. TC regularly holds workshops to educate land owners and public managers about riparian ecology (riverside areas) and how to manage invasive species on their property. With the right knowledge, land owners can proactively improve their properties so that tamarisk is managed, allowing native species to thrive. The group also coordinates with a number of organizations across the Southwest in order to share new ecological research and provide assistance at specific restoration sites, such as the years-long project to restore the banks of the Dolores River, a major tributary of the Colorado River.
Beating Them with Beetles
Another approach to tamarisk is biological control, a process that entails introducing natural predators to the invasive species. Of course, fighting one non-native species with another might sound like the creaking hinge on Pandora’s Box, but there are ways to assess the potential impact of new species before releasing them into the wild. That’s exactly what the US Department of Agriculture did with the tamarisk beetle, an insect native to Eurasia that eats tamarisk. After 10 years of close study, the USDA released the beetle into the wilds of the Southwest in 2001.539px-DiorhabdacarinulataFukangChina
Almost fifteen years later, the beetles have spread to every southwestern state and have proven to be an effective tool in controlling tamarisk. But it turns out that as the tamarisk beetle has become established, the population of Southwestern Willow Flycatcher, a species of bird found in its namesake region, has declined. This is because as tamarisk displaced native willow along many western rivers, in many areas the bird was forced into using tamarisk for nesting, due to its similar branching structure.  As the beetle moves into an area and causes tamarisk defoliation, the birds nesting in tamarisk are left with literally no roof over their heads. Without leaf cover, nest temperature increases, as does visibility to predators.
TC and other concerned groups realized this possibility back in 2007, and have since worked with the Colorado Department of Agriculture and the Marine Science Institute at UCSB to devise ways of tracking the spread of the beetle. The Coalition’s work in this regard helps land owners anticipate the arrival of the beetle so they can learn how to incorporate it into their existing land management practices (e.g. plant native willow before the beetle arrives in the area).
Restore. Connect. Innovate.
Riparian environments are among the most important in nature. They support biodiversity, help to conserve the soil, and have a tremendous impact on wildlife. That’s why the research and restoration activities of the Tamarisk Coalition are so vital. Their work helps to restore not only Colorado’s rivers, but riparian environments throughout the western US. Towards that end, the Coalition hosts a conference every year on the latest techniques and research in the field. It affords all scientists and conservationists the opportunity to connect, discuss, and innovate new ways of dealing with habitat loss and invasive species.
To learn more about the Tamarisk Coalition or to get involved with their river restoration efforts, visit them at www.tamariskcoalition.org and on Facebook.

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