Since its introduction to southeastern Utah and western Colorado many years ago, the tamerisk has taken over many waterways in the Colorado Plateau. Today, a beetle that is a natural enemy to the plant is killing them in the Grand County area and moving up the Green River and tributaries.
(This is the final in a three-part series on the invasive tamarisk species and its control in southeastern Utah.)
While his job title would seem pretty specific, Bureau of Land Management fuel program manager Brian Keating has a good deal to think about aside from whether or not something will burn.
"We don't want to just remove the tamarisk and Russian olive and walk away," Keating said. "We want to really focus on watershed restoration, and that involves revegetation with native species, as well as additional noxious weed controls. When you remove big sections of the tamarisks, it opens the ground up, and any disturbance to the ground becomes a really desirable spot for other noxious weeds, like cheat grass or Russian knapweed and things like that, so we have to follow up with treatments for those species."
This is an issue because the tamarisk is going away on its own. Or, to be more accurate, it's going away with the help of the tamarisk beetle, a small, striped insect which somehow missed the boat when tamarisk trees, also known as salt cedar, were imported to North America from Asia in the 1800s. Without the beetle, the trees took over much of the west, especially desert riparian zones.
The beetle was introduced to Grand County in 2004, and it has had remarkable success. While it was only released in limited areas near Moab, it has spread as far north as the Book Cliffs, as far south as Cataract Canyon, and it's working its way up the Green River from the confluence of the Green and Colorado rivers.
"We were seeing some good brownout at Mineral Bottom," Grand County weed supervisor Tim Higgs said. "So the beetles are there, though they may have hitchhiked on some boats. We're still waiting for someone to tell us they've made it to Lake Powell, but we haven't heard that yet."
"Brownout" is what happens to stands of tamarisks when they're infested with the beetles. The insects devour the plant's foliage, leaving it brown and dying. "It's basically not even transpiring, because there's no green to produce photosynthesis," Higgs said of the stressed tamarisks. "So the native plants along the river are actually getting a little more water."
Tamarisks are notorious for their ability to suck up water, out-competing native species at the same time the invasive plants contaminate the soil with salt, preventing the natives from reseeding. However, even after the tamarisks are gone, the natives need help to reestablish the natural ecosystem.
"This past winter was the removal component, and this spring we've done the revegetation work in the Goose Island campground," Keating said. "We've even gone to the extreme of putting in an irrigation system to make sure those plantings would establish and prosper. So far they have; we haven't seen any mortality and I think we've already got three feet of growth on those things, and they've only been in the ground about a month and a half."
That's the sort of growth Keating would normally expect in a disturbed areaâexcept from tamarisks. "What we've seen in some of our past treatments where we've mechanically removed the tamarisks, they naturally resprout unless you use some kind of herbicide treatment," he said. "In a normal year, before the tamarisk beetle was here, those sprouts would, in the course of one year, probably put 10 feet of growth on. What we've seen now, is the stuff that we cut last fall resprouted, but the beetles hit it right away, and they're only getting one or two feet tall before they're shut right down."
With the tamarisks failing to thrive, the BLM and other landowners represented in the partnership will need to guide the river corridor's recovery, especially in terms of helping native species take over before other invasive species move in.
"One thing that we've benefited greatly from is the Utah Partners for Conservation and Development," Keating said. "The goal of the UPCD is watershed restoration, and they've got some focus areas. One of the focus areas is the Colorado River corridor as it goes through southeast Utah."
"I submitted a $37,000 proposal asking them to buy trees, and native grass seeds, and shrubs, so that I could revegetate the work where I'm doing the removal," Keating said. "That was funded, so this fall we have about 3,500 trees coming, a mix of cottonwoods and willows that we're going to be planting up and down the Colorado River Corridor. Then we're also getting about 100 acres worth of native seed grass and shrub mix."
While some areas will be left to natural processes for reclamation, Keating said tamarisk partners will take an active role in restoring the river corridor where it's feasible. "We will continue to do treatments and remove it where we can," he said. "There's a short term and a long term, and I think we're coordinating very well, we're learning a lot, we're hitting the priority areas, and everybody's doing a lot of monitoring to find out what's going to give us the most bang for the buck, and most importantly, what's the most effective."
The BLM has also posted information about the tamarisks and their control at key points along the corridor, especially campgrounds. Keating hopes that has effects beyond just mollifying campers who are put off by the clear-cut facilities.
"Trying to educate the public is definitely an important component of this," Keating said. "We get a lot of visitors who come to the area that don't know anything about the tamarisk, and I've had folks walk up to me and want to know what the tamarisk was when they're in full bloom, with their purple flowers, because they want to get some and bring it back home to plant it in their yards in Wyoming. That just makes us cringe."