Click here to read the report. Here’s the executive summary:
In 2001, the U.S. Department of Agriculture approved the release of a biological control agent, the tamarisk beetle (Diorhabda spp.), to naturally control tamarisk populations and provide a less costly, and potentially more effective, means of removal compared with mechanical and chemical methods. The invasive plant tamarisk (Tamarix spp.; saltcedar) occupies hundreds of thousands of acres of river floodplains and terraces across the western half of the North American continent. Its abundance varies, but can include dense monocultures, and can alter some physical and ecological processes associated with riparian ecosystems.
The tamarisk beetle now occupies hundreds of miles of rivers throughout the Upper Colorado River Basin (UCRB) and is spreading into the Lower Basin. The efficacy of the beetle is evident, with many areas repeatedly experiencing tamarisk defoliation.
While many welcome the beetle as a management tool, others are concerned by the ecosystem implications of widespread defoliation of a dominant woody species. As an example, defoliation may possibly affect the nesting success of the endangered southwestern willow flycatcher (Empidonax traillii extimus).
In January 2015, the Tamarisk Coalition convened a panel of experts to discuss and present information on probable ecological trajectories in the face of widespread beetle presence and to consider opportunities for restoration and management of riparian systems in the Colorado River Basin (CRB). An in-depth description of the panel discussion follows.
The panel concluded that as the tamarisk beetle moves into the Lower Colorado River Basin (LCRB), the selection of management actions to support a transition to a healthy riparian system will depend on the unique suite of characteristics of each sub-basin and the goals of basin managers.
The panel emphasized the importance of basin-specific planning, the necessity of monitoring and inventorying to inform management, and that adaptive management practices will be essential for success relative to varying goals. The panel developed a framework to assist managers in selecting appropriate management strategies and identified future research needed to further inform restoration approaches and management decisions.
Just because there hasn’t been as much talk about tamarisk lately doesn’t mean the invasion is over. Now, talk has begun again, but the message has changed.
Eradication is out; control is in.
While tamarisks, or saltcedars, are watergulpers, a fully grown tree uses only about 20 gallons a day, not 200 gallons as mistakenly was often reported in the past.
And trees should be taken out for a reason, and with a plan, not just because they are bad invaders.
Those messages have been conveyed twice in the last week by the Tamarisk Coalition to area conservancy districts. Based in Grand Junction, the group incorporated in 2002. The group works with other organizations to improve habitat, not just wipe out saltcedars.
“In a nutshell, what we do is help people restore rivers. We’re focused on that,” Stacy Beaugh, executive director of the Tamarisk Coalition, told the Southeastern Colorado Water Conservancy District board last week. “You can’t just cut them down and walk away.”
She assured the Southeastern board, which took the lead in earlier tamarisk removal programs for the Arkansas Valley, that Southeastern Colorado remains a high priority.
A few days later, the Lower Arkansas Valley Water Conservancy District heard from Rusty Lloyd, program director with the Tamarisk Coalition.
Lloyd explained that the group no longer is concerned with completely removing the trees, many of which were purposely planted for erosion control. But it supports efforts to remove pockets of the plant where possible and natural controls such as beetles to knock back the numbers.
“The beetle can weaken the plants, and some plants don’t come back,” Lloyd said. “It seems to be doing its job, but it’s sporadic.”
Lloyd said there are water quantity and quality benefits from removing tamarisk, but the purpose for any program should look at other issues such as improving wildlife habitat. A plan should be in place to replace tamarisk with more beneficial species.
“There are lots of invasive species we are concerned with,” Lloyd said. “We don’t blindly advocate people tearing out plants. You need to have a purpose.”
Past efforts to remove tamarisks have not always worked and sometimes cleared the way for other invasive species to take hold.
“We learn as much from our failures as we do from our successes,” Lloyd said.
Tamarisk leaf beetle
Tamarisk leaf beetles at work
2014 Tamarisk leaf beetle distribution map via the Tamarisk Coalition
A workshop next month will look at repelling invaders from area waterways.
Specifically, tamarisk, Russian olives, elms and other introduced plants to riparian areas that detract from natural vegetation and habitat.
The seventh annual Arkansas River Watershed Invasive Plant Partnership Workshop will be held Oct. 5-6 at the Pueblo Convention Center, 320 Central Main St. Activities begin at 9:30 a.m. Oct. 5. A $20 fee covers lunch on both days, snacks and a field trip.
Topics in the classroom will include setting goals for restoration, case studies on restoration, seeding, weed management and two field site visits to view recent restoration work. The field trip will feature equipment demonstration and a discussion on how to use native materials for revegetation.
From email from the Ditch and Reservoir Company Alliance (John McKenzie):
Hello DARCA Members –
I am attaching the finalized agenda for our workshop and float trip on Sep 24-25. We are in the process of opening up participation to non-DARCA members so please register this week to secure a spot. You may go to the DARCA website to register and will need the code, 6JILB409. (Look under the Workshops tab)
Will see some of you in a couple of weeks.
If you have any questions, please give me a call.
Ditch and Reservoir Company Alliance
1630A 30th St., #431
Boulder, CO 80301
From the Grand Junction Free Presss (Shannon Hatch):
Have you noticed anything missing in the Grand Valley lately? Perhaps you’ve been out biking on the Colorado Riverfront Trail, walking along Connected Lakes, playing disc golf at Matchett Park, rafting the Colorado River, or driving along Monument Road and thought — hmmm — something is different here. I think there used to be more trees. Why did someone remove them? Is something going to take their place?
Recently, a number of organizations and individuals, including Colorado Parks & Wildlife, City of Grand Junction, Mesa County, Natural Resources Conservation Service, Tamarisk Coalition, and various private landowners have been undertaking a variety of riverside restoration projects along the Colorado River and its associated washes, from Palisade to Fruita. Much of this work is being completed under the umbrella of the Desert Rivers Collaborative (DRC), a public-private partnership dedicated to improving habitat along the Colorado and Gunnison Rivers in Mesa and Delta counties.
One of the main focal points of the DRC is the management of invasive plant species, including tamarisk (also known as salt cedar) and Russian olive, which can degrade the ability of areas along rivers and streams to provide essential habitat and resources for humans and wildlife alike. Tamarisk and Russian olive’s dense growth patterns can block access for recreation and agriculture, create hazards for river runners, invade popular campsites, channelize waterways, and, in the case of tamarisk, facilitate increased wildfires. Both species displace native vegetation, which negatively impacts fish and wildlife habitat, and water usage by these plants can also be substantial, most notably in areas where these species displace less thirsty plants, such as sagebrush and rabbitbrush.
Visually, as many of you may have noticed, initial removal of tamarisk and Russian olive can be quite dramatic. Due to the scope and densities of infestations, heavy equipment is often utilized to mulch trees across large acreages, leaving behind areas that some have likened to a “bomb blast” zone. And then there’s the issue of secondary weeds: some of our valley’s finest — including kochia, whitetop, Russian thistle, cheatgrass and perennial pepperweed — take a liking to these recently disturbed sites, often setting up shop in high-density.
Restoring habitat along rivers and streams is typically a multi-staged event, with initial removal merely the first act. In addition to on-going monitoring and maintenance, treatment of tamarisk and Russian olive resprouts, secondary weed spraying, and revegetation with native plants are also key components, and ones that often require a phased approach. For example, in order to avoid damage to desired plant species, revegetation activities may need to be put on hold until completion of herbaceous weed spraying, a process that can last several growing seasons.
Fortunately, landowners and managers in the Grand Valley are no strangers to the hard work and ongoing attention that these projects require. And thanks to more flexible grant funding, managers are now able to better plan for the myriad steps, often required over a multi-year time frame, needed to achieve restoration success. ˆ
As an example, 24 acres of tamarisk and Russian olive were treated at the Connected Lakes Section of James M. Robb Colorado River State Park in the winter of 2013. Resprouts and secondary weeds were sprayed at various stages in 2014. Revegetation with native plants, including grasses, forbs, cottonwoods, willows, and various shrubs, occurred earlier this year, with monitoring and maintenance an ongoing priority. In a testament to the importance of monitoring, Pete Firmin, park manager, noted that 15 cottonwood trees were lost in a single weekend to beaver activity, prompting changes in how the trees were protected. Pete also noted that “patience and planning are important in restoration work. Throughout the process we encourage the public to visit these sites and talk with the area manager about the ongoing plans for the land.”
While some of your favorite areas in town may currently be looking a bit bare, rest assured that restoration actions to improve these riparian habitats for the betterment of the community are underway. The legacy of invasive species impacts can’t be erased overnight, but with time, great improvements in the structure, function, accessibility, and enjoyment of these areas can be realized.
If you are interested in touring local restoration sites up-close and personal, consider joining Tamarisk Coalition on their annual Raft-the-River trip on Aug. 23. Rimrock Adventure guides and hand-picked local river experts will provide an informative, fun float down the Colorado River with après dinner, drinks, live music, and prizes to boot. For more information on the raft trip or to learn more about local restoration projects, please contact Tamarisk Coalition at 970-256-7400 or visit http://www.tamariskcoalition.org.
Shannon Hatch is restoration coordinator for the Tamarisk Coalition. This is part of a series of articles coordinated by the Water Center at Colorado Mesa University in cooperation with the Colorado and Gunnison Basin Roundtables to raise awareness about water needs, uses and policies in our region. To learn more about the basin roundtables and statewide water planning, and to let the roundtables know what you think, go to http://www.coloradomesa.edu/WaterCenter. You can also find the Water Center at http://www.Facebook.com/WaterCenter.CMU or http://www.Twitter.com/WaterCenterCMU.
From the Colorado Springs Post Independent (Pam Zubeck):
Because of the plant’s resistance to heat and drought, the Army Corps of Engineers used it in the mid-19th century to stabilize riverbanks against erosion. Then, during the severe drought of the 1930s on the Great Plains, farmers deployed it and its companion, invasive Russian olive, to provide windbreaks.
In the decades since, the story has shifted. Tamarisk, which can grow to 20 feet tall, has proliferated with a vengeance, colonizing thousands of miles of riparian corridors in the West, including those along the Front Range. It guzzles water, squeezes out any competitors, and sterilizes wetlands by leaving soils parched with salinity — hence its other name, saltcedar.
Besides being hard to destroy, a single plant’s blossoms produce thousands of seeds, which easily take root. Tamarisk, by one account, has multiplied 150-fold in just 100 years and now occupies up to 1.5 million acres in the western United States.
Even as water resources are taxed amid drought conditions, this ever-spreading exotic drinks freely via taproots that can reach 50 feet into the ground. One analysis put its consumption of water along the Arkansas River between Pueblo and the Kansas state line as enough to serve 376,000 people annually.
The body of research on the plant is massive and growing. Many have taken up the cause of eradication: government agencies, nonprofits and thousands of volunteers, as well as scientists and researchers, including a Colorado College botany professor and his students. Congress even adopted a law in 2006 ordering the Interior and Agriculture departments to get involved, though significant funding was never allocated.
Some new strategies for controlling tamarisk — including deployment of an insect, which has grown controversial due to its destruction of habitat for an endangered species — show promise. But the war on tamarisk is far from over, and warming temperatures due to climate change could help it spread farther by creating hospitable conditions in new areas.
Its role as villain may be relatively new, but tamarisk has fully embraced the part by being very hard to vanquish.
According to the Global Invasive Species Database, there are three varieties of tamarisk on Earth: tamarix aphylla (shrub), tamarix parviflora (tree) and tamarix ramosissima (tree, shrub). The last type prevails in the American West, in a spread the database refers to as “a massive invasion.”[…]
Eradication efforts began on the local level sporadically in the 1940s, but didn’t get traction on a wider scale until the 1990s, when a project on the Rio Grande River south of Albuquerque was undertaken.
About 15 years ago, the Tamarisk Coalition was formed. Today it works with more than 100 partners to restore riparian lands overrun with tamarisk through education and removal projects.
Some of those were undertaken along the Dolores and Colorado rivers with the help of Troy Schnurr, a ranger with the Bureau of Land Management in Grand Junction. The stretch Schnurr and others worked on isn’t accessible by heavy equipment, so crews had to raft down the river, work by hand with chainsaws and apply herbicides to stumps.
The project covered 25 miles and took 15 years.
“It can be overwhelming when you start,” Schnurr says. “There’s a lot of repair work, reseeding, replacement because the tamarisk has been there so long. That plant’s gonna be around for quite a while.”
Shelly Simmons, assistant district forester with the Colorado State Forest Service, explains it like this.
“What happens is resprouting,” she says. “Tamarisk has an aggressive root system. Once it does get established, you’re going to have to watch it for five years and treat it for regrowth. It’s rare if you get 100 percent control the first time you try to control it.”
Simmons works with volunteers, land owners and various agencies, including conservation districts, attacking tamarisk in the Purgatoire basin, Chico Creek, Fountain Creek, Huerfano Creek and the main stem of the Arkansas River.
“There’s been a lot of workshops in the Lower Arkansas Valley over the years,” she says. “We focus on riparian restoration, so we’ve had a lot of land managers and land owners attend those workshops. If a landowner feels they have the equipment and the means, they can undertake projects on their own land.” That was the case in an area along the Arkansas east of Pueblo and south of Highway 50, where tamarisk was cut and piled into heaps several years ago…
The act did result in a peer-reviewed assessment of tamarisk, though, completed in 2010 by the U.S. Geological Survey. That assessment puts a lot of stock in saltcedar leaf beetles (Diorhabda elongata), citing a study area in Nevada that showed a 65 percent mortality rate in saltcedar five years after the beetle was unleashed there. The beetles “consume saltcedar leaves, depleting root energy reserves until they are exhausted and the plant dies,” the assessment says.
These beetles came to Colorado about a decade ago, Beaugh says. Initially imported from Asia where the plant originated, the beetles are collected from areas on the Western Slope, where they’re well-established, and housed at the Palisade Insectary, run by the Colorado Department of Agriculture’s Biological Pest Control Program. From there, they’re shipped around the state, including to the Arkansas River corridor and Fountain Creek.
They arrive in cardboard jugs that resemble ice cream containers. Simmons says workers perch the cartons amid tamarisk bushes, and simply open the lids. The beetles, 1,500 per jug, crawl out and go to work. About 10,000 beetles are released per site, Simmons says, ideally “where tamarisk trees are younger and more succulent.”
A Colorado Agriculture Department newsletter says the beetle had settled into the Arkansas Basin by 2012, where some sites have been defoliated multiple times and up to 60 percent of the target tamarisk trees have been killed. The state has taken to calling the beetle “a valuable management tool.”
It also lies at the heart of the CC professor’s latest research. Heschel wants to know how the beetle affects tamarisk’s consumption of water; data to date suggest that in some cases, a tamarisk plant under siege only gets more aggressive.
“When the beetle attacks tamarisk,” Heschel says, “tamarisk tends to increase its water use to compensate for getting attacked.”
The study, which includes one site just south of the Fountain Creek Regional Park Nature Center, also looks at whether tamarisk that survive the beetle attack somehow become even heartier and more thirsty. “Is that what we’re accidentally doing?” Heschel says. “I don’t know the answer to that.”[…]
Use of the beetle, however, is being curtailed in some other states due to its potential to destroy habitat for the endangered southwestern willow flycatcher. In September 2013, the Center for Biological Diversity, and the Maricopa Audubon Society, in Arizona, filed a lawsuit against the U.S. Department of Agriculture, alleging the beetles were destroying the songbird’s nesting areas. The lawsuit, according to the Los Angeles Times, accused the department’s Animal and Plant Inspection Service of failing to protect the flycatcher, which nests in tamarisk thickets. The case is pending before a federal judge.
Robin Silver with the Center for Biological Diversity says while the lawsuit points to problems in Utah, Arizona and Nevada, the beetles also have invaded nesting areas in southwest and south central Colorado. “[Federal agriculture officials] said, ‘Don’t worry, because the native plants will come back,'” Silver says. But he argues that “unless you change the hydrology, you’ll end up with nothing” in the way of vegetation after tamarisk has been removed. “The only chance you have,” he says, “is to get out ahead of the beetles and change some of the hydrology for plant recovery. [Officials] don’t want to do that because it costs money.”
Patrick Shafroth, a research ecologist with the USGS at the Fort Collins Science Center, agrees that restoration is crucial in determining what vegetation comes next in the context of tamarisk control. As stated in a 2011 paper by USGS and other researchers about consequences of using the beetle, “Conditions in many areas now occupied by tamarisk have been so altered anthropogenically that recolonization by native willows and cottonwoods is unlikely without intensive restoration efforts.”
Considering the sky-high cost and massive efforts to restore large areas affected by the beetle, the paper says, “widespread tamarisk mortality will likely result in a net loss in riparian habitat for at least a decade or more.”[…]
And then there’s the wild card of climate change. Despite all attempts to rid rivers and streams of tamarisk, the hearty plant could get a leg up from rising temperatures. While Shafroth considers the question of climate change’s influence “uncertain,” the 2010 USGS assessment and other scholarly works say it could foster tamarisk’s proliferation, given that it thrives in hot, dry weather, and parts of Colorado remain in moderate to severe drought conditions.
From the assessment: “Further expansion of saltcedar northward (and to higher elevations) is likely to occur due to climate warming.”
All of which makes Shafroth wonder if this scoundrel of the West is a cause, or merely a symptom, of the real problem.