Fourth in an occasional series examining issues facing Utah’s national parks.
Canyonlands National Park • Larry Aberback studied the banks of the Colorado River in quiet reflection and then posed a question many of the others on the commercially guided float trip had silently wondered.
“What happened to all those dying bushes? Is it drought?” the elementary school teacher from New York City asked during a trip through Cataract Canyon in July. “It’s kind of sad.”
Sad, in this case, is in the eyes of beholder. The dying stands of bushes are tamarisk — a non-native, invasive species from Eurasia introduced to the American West more than a century ago. Tamarisk has taken over the banks of many Western rivers and is particularly thick along the Colorado in Canyonlands.
People sitting in the raft next to Aberback had a totally different view of the dying bushes. As Westerners involved in the environment, they saw the defoliating of tamarisk as a step in the right direction to allowing the return of native species.
The question then remains: is the death of tamarisk sad or long overdue?
National Park Service officials say evidence of tamarisk along the river corridor dates back to the early 1900s. Pictures of tamarisk from 1914 show it was well established by then. Controlled flows from dams upstream seem to have helped the invasive species thrive starting in the 1950s long before 257,400 acres in southeast Utah became Canyonlands National Park in 1964. The park was eventually expanded to more than 337,000 acres. Some groups and citizens are now seeking further protection of the land around the park in the form of a proposed Greater Canyonlands National Monument.
The war against tamarisk in the West has taken many forms through the years — cutting, burning and poisoning — but researchers with the U.S. Department of Agriculture finally found something that appears to be making a major difference by visiting the homeland of the plant to bring it to the battle.
Tamarisk leaf beetles were released along the Colorado River in 2004, upstream of Canyonlands National Park. Other releases happened in 2005 and 2006. It didn’t take long before the work of the beetles was evident along the entire stretches of both the Green and Colorado rivers within the park.
The beetles are still at work — it takes several cycles of infestations to actually kill tamarisk stands — but some wonder if it was necessary and others filed a lawsuit against the Department of Agriculture to re-evaluate the program.
“Some people are looking for a return to the [19th century explorer] John Wesley Powell times. We will never see that. We have these large dams that control the flows and we have manipulated all these different elements,“ said Steve Young, a longtime backcountry river ranger in Canyonlands. “The system was kind of going into a balance with tamarisk and now we have screwed it up again.”
For decades, tamarisk was viewed as a water-sucking, wildfire-enhancing, bank-choking, do-nothing-for-wildlife invader. Federal and state governments continue to spend millions in an effort to control tamarisk.
More recently, researchers are finding tamarisk does have positive impacts on river ecosystems and some wildlife species have figured out how to use it. Birds common to riparian areas often use tamarisk for nesting, including the endangered southwestern willow flycatcher.
The Animal and Plant Health Inspection Service of the Department of Agriculture stopped releasing beetles in response to the 2009 lawsuit brought by the Center for Biological Diversity to protect species like the willow flycatcher, but the cat was already out of the bag, so to speak.
“Given that the beetles are already on the ground this was a less than satisfactory result,” said Noah Greenwald, endangered species program director for the Center for Biological Diversity. “We are not fans of tamarisk, but simply removing it with an invasive species only completes half the job because it fails to address the changes in hydrology and habitat that let tamarisk take over in the first place and thus provide no assurance that native riparian vegetation will take tamarisk’s place. This is harmful to the flycatcher and many other species.”
Mark Miller, chief of Resource Stewardship and Science over Canyonlands, says the beetles appear to have achieved extensive mortality on some tamarisk stands while others appear less impacted.
The beetles move in, defoliate the tamarisk and move to the next stand. If the tamarisk survives the first wave, the beetles return to do their work again and so on, until the tamarisk dies.
“In areas where tamarisk has been impacted we are seeing a pretty rapid response to take its place from some native vegetation,” Miller said. “In many places coyote willow has replaced tamarisk on a one-to-one basis.”
The willow, according to a theory, probably would have taken advantage of the unvegetated sand bars left intact by controlled dam regimens. On the downside, there appears to be a number of other non-native plants — like Russian olive thorn trees — primed to jump in and fill the void if tamarisk disappears.
There are other unexpected benefits of the thick tamarisk stands lining the rivers of Canyonlands National Park.
“We have some of the best archeological resources in the country and they are protected by tamarisk,” Young said. “It is a pretty effective barrier to most visitors. You have to be stupid or a park ranger to crawl through some places. I can’t ask for a better way to protect them.”
One thing visitors along the Colorado in the national park instantly notice about the demise of tamarisk is the lack of shade during blistering mid-summer days.
Ranger Young has been working to remedy that by planting native cottonwood trees in key locations at popular stops and campsites along the river. The National Park Service has planted 55 trees in the river corridor.
“Dying tamarisk is not a fun thing to sit under on a hot day,” said Tim Gaylord, operations manager for Holiday River Expeditions. “We use times like those as an opportunity to talk with our guests about invasive species and their ability to proliferate and change the course of the river, literally. Seeing the huge stands of dead and dying tamarisk really shows the scope and scale of the impact of tamarisk.”
Five things not to miss at Canyonlands National Park
Sunrise or sunset at the Grand View Point Overlook in the Island In The Sky District.
A river trip on the Green or Colorado rivers.
Mountain biking the White Rim Trail.
Hiking to the Great Gallery pictograph panel in the Horseshoe Canyon Unit.
Visiting the Doll House, a collection of sandstone pinnacles, domes, hoodoos and tower formations accessed via a very rough 4-wheel-drive road or a 1,000-foot hike from the Colorado River.
For more information on Canyonlands National Park, go to http://www.nps.gov/cany/index.htm.