Crews remove Russian olive trees by hand along the Escalante River in Glen Canyon National Recreation Area/Kurt Repanshek
Traveler Special Report: Vegetative Invaders In The National Parks
By Kurt Repanshek
Ducking and weaving around branches and avoiding patches of prickly pear cactus, all under a glaring sun in midday heat climbing towards 100° Fahrenheit, the crew scanned the thick vegetation along the Escalante River deep within Glen Canyon National Recreation Area for the showy, silvery leaves of a tree that shouldn’t be here.
Though long considered a lovely ornamental able to break the wind, provide shelter from the sun, and slow erosion, Russian olive more recently has been branded a noxious weed on public lands, one that will overrun native willows and cottonwoods that normally crowd riverbanks, and even mute the natural, and needed, floodwaters that monsoonal rainstorms can spur.
The U.S. Forest Service views the species as “problematic in the Southwest because it favors riparian communities and other moist environments.”
“As populations increase, Russian olive crowds out desirable native riparian trees such as cottonwood and willow, thereby reducing flora and fauna species diversity. Because of its ability to colonize streambanks, Russian olive can alter the natural flooding regime and reduce availability of nutrients and moisture,” the agency said in a 2014 publication.
Glen Canyon NRA in southern Utah and northern Arizona embraces more than 1.2 million acres. It’s impossible to say how many of the acres that cup the Escalante, Dirty Devil, Colorado, and San Juan rivers, and their own tributaries, that ripple through the NRA have been invaded by Russian olive. But across the Escalante River watershed on the western side of the NRA the trees are found on at least 5,327 acres on U.S. Bureau of Land Management, U.S. Forest Service, National Park Service, state, and private lands, Jonathan Paklaian says.
Paklaian should know. He’s conservation programs manager for Grand Staircase Escalante Partners, a nonprofit organization that, among other things, oversees crews of Utah Conservation Corps volunteers who bushwhack into the backcountry on Russian olive search-and-destroy missions.
“We’ve been working for a number of years with Escalante River Watershed Partnership, since 2009, to remove Russian olive throughout the watershed,” Paklaian told me after we hiked five miles under that unrelenting sun on a hot July day from the nearest road down to the Escalante River within Glen Canyon NRA. “That’s a 1.3-million-acre watershed. Much of that is in Glen Canyon National Recreation Area. That’s the southernmost section of the watershed. We employ several people, two field staff and me, but also a number of conservation corps crews to help us with removing and treating Russian olive.”
Russian Olives Are Just Part Of The Problem
Across the National Park System, an estimated 2 million acres -- at least -- have been invaded by non-native vegetation. Climatic changes are inviting more invaders, which means more troubles for the native vegetation.
“Because they fragment native ecosystems, displace native plants and animals, and alter ecosystem function, invasive exotics represent one of the most serious threats to natural ecosystem integrity,” say scientists at the National Park Service’s Sonoran Desert Network office. “They can also alter fire regimes, for instance, by causing fires to burn more swiftly or intensely, or even introducing fire to systems that did not evolve with it.”
And that’s just in one corner of the roughly 85-million-acre National Park System. Look out across the landscapes and the invasive species stand out:
Everglades National Park and Big Cypress National Preserve, Florida
Melaleuca, a subtropical tree native to Australia, New Guinea, and the Solomon Islands arrived in South Florida in the early 1900s for, the Park Service says, “swamp drying.” Unfortunately, in Everglades National Park the tree spreads quickly, pushes out native species such as sawgrass, and is a risk to the park’s marshes, wet prairies, and aquatic sloughs. With each mature tree able to spread upwards of 100 million seeds, the battle won’t be easily won. Aiding the Park Service in the battle are insects native to Australia that are the trees’ natural enemies. Physically removing the trees is another option, as is the use of herbicides.
Brazilian pepper is another invader, a South American native evergreen that “produces chemicals which appear to suppress the growth of other plants. It is fire resistant and salt tolerant. Considered one of the most invasive plants in Florida,” notes the Park Service.
Appalachian National Scenic Trail
Garlic mustard, a culinary herb, is among the exotic species growing along the Appalachian National Scenic Trail. Kudzu, multiflora rose, and Chinese silvergrass also have invaded the trail’s nearly 2200-mile-long corridor, which just might “harbor more rare, threatened and endangered species than any other National Park Service unit,” according to the Appalachian Trail Conservancy.
National Park of American Samoa, American Samoa
Lopa tree (South Asian native) is a prolific seeder that outcompetes the growth of native trees. Its impact reaches the waters of National Park of American Samoa, as the species is a nitrogen fixer, which leads to bleaching of the park’s coral reefs. However, locals see the tree as having medicinal values, and so the Park Service has allowed it to remain on Ofu.
Saguaro National Park, Arizona
Buffelgrass (native to Africa, Asia, and the Middle East) and Stinknet (native to South Africa), non-native grasses that are more flammable than native grasses and so can result in a more frequent fire cycle in the Sonoran desert, that is not fire adapted.
Fort Pulaski National Monument, Georgia
Invasive phragmites, a reed, has been an issue on the monument grounds, while a fern, Chinese ladder brake fern, has attached itself to the outer walls of the fort and is undermining the mortar.
Hawai'i Volcanoes National Park, Hawai'i
Kahili ginger flower is overrunning parts of Hawai’I Volcanoes, where it arrived about 50 years ago from the Himalayan region of India, according to the Park Service. It was introduced to Hawaii, the agency adds, “because it’s pretty.”
“But once these Kahili ginger sprout in an area, they rapidly reproduce and sort of unroll like a carpet and eliminate all of the undergrowth,” the park added in a report on invasive species. “So we immediately lose a lot of our diversity. And that deteriorates the health of the forest.”
You can rather easily find invading species elsewhere in the park system. Yosemite National Park has more than 130 non-native plant species, among them Yellow starthistle that has a longer tap root than many natives and so can deprive the native plants of water. Theodore Roosevelt National Park in North Dakota, with its harsh landscape and equally harsh climate, grapples with invasive species.
“Leafy spurge is a plant species that's particularly problematic in Theodore Roosevelt,” said Terri Hogan, the Park Service’s point person for invasive vegetation. Parks in Alaska also are on “the verge” of having a significant invasion of non-native vegetation because of the changing climate, she added during a conversation about invasives in the parks.
Cheat grass is another non-native nuisance that “changes the ecology once it invades,” Hogan pointed out. “Many of the systems it invades are not fire prone, or fire occurs at very long intervals. And it changes that dramatically, to very short intervals, and the fire is very hot. So it just destroys the native habitat, and destroys habitat for native animals as well. And it completely changes the ecology of an area and threatens the native species that occur there.”
Farther north, in Alaska, Park Service personnel are "watching for species and trying to intercept them before they enter parks,” she added.
"There are a number of species of knotweed that can be very difficult to control that undermine roads and bridges and break up foundations of homes. And they occur along streams and rivers and are, again, very difficult to control," Hogan explained. "So there are a number of species that are hard to control, relatively widespread, and really change the environment once they're introduced."
At Acadia National Park in Maine, Japanese knotweed is a particularly troublesome invader.
"Imagine a plant that can burst through pavement or sneak in through foundation cracks in your house! Their invasions tend to be sudden and aggressive, making them successful almost globally," reads a section of the park's website. "The invasive plant management team at Acadia National Park are actively managing stands of Japanese knotweed on parklands. This is done mainly through yearly cutting of stalks and the application of herbicides to regrowth from rhizomes.
"There is hesitation to fully dig up the root systems as this may damage native plants, increase soil disturbance, and is very time consuming. It is also rare that this approach would actually end in complete removal, as even one root fragment left behind is able to grow new stems."
Terence Ruane, who has been working on invasive species control since 2004 for Cardno, an environmental consulting firm that works with the Park Service in some areas, said Japanese knotweed is a tough invader to remove once it's entrenched.
"That one's really nasty. I don't really know of a great way to treat that one, other than what they call 'hollow stem injections.' Where you really go in there with a specially designed hand sprayer and essentially put a millimeter of chemical into each stalk," he said. "Even if you top kill it in early spring, it just comes back. You really have to try super hard to target that root growth. Target what's under the soil more so that what's above ground."
Across the park system, as many as 36 units have been battling Japanese knotweed.
Stalking Russian Olive At Glen Canyon
But why remove Russian olive? Its silvery leaves and its yellow blossoms, when they erupt in early summer, provide a contrast to the greener willows and cottonwoods. Birds feast on the seeds (and pass them through their digestive systems to spread them), notes the Forest Service, as do coyotes, deer, and other small animals. And, decades ago, it was viewed as a great aid to communities in the Southwest.
“It was planted intentionally in towns in the area for a lot of reasons. Some of those include windbreaks and erosion control,” Paklaian explained as we rested along the cooling river. “But it’s very good at erosion control. So good that it changes the way the river flows. And it armors the banks and creates a channelized river, which is not really what a desert river does. And so that affects not just the plants, but the habitat for fish and wildlife. It was identified as the biggest threat to the ecosystem here.”
Russian olive along the Escalante River before treatment/Grand Staircase Escalante Partners
The same stretch of river after Russian olives were removed/Grand Staircase Escalante Partners
We saw the natural process literally in motion later in the day. After an afternoon thunderstorm forced us to retreat to our tents for an hour or so, we regrouped along the placid river for dinner. Sitting there, chatting while we ate, we were interrupted by the sound of the river, now growing in strength, width, and depth, and steamrolling a mound of vegetation downstream. It was a flash flood, two hours after that afternoon storm.
Fortunately, we were not in a slot canyon but in a wide bench that allowed us to watch in awe as the Escalante grew in force and debris, widening from a few feet across earlier in the afternoon to a more river-like 20 or so feet across. A gravel bar I had walked across that afternoon was now under the swirling chocolate water, the unseen rocks clacking, grinding, tumbling, and complaining as the river rearranged them.
This – the widening of the river under the flash flood, the pushing of debris and sediments both out to the sides of the normal flow corridor and downstream – is the Escalante’s normal behavior, one that Russian olive could strangle if left unchallenged.
“Desert rivers are supposed to be dynamic, and flooding is a big part of this,” said Alex Engel, who works with Paklaian. “Floods take out banks and create new channels. This allows plants to have new habitat to grow into, and fish need variety, like riffles and pools, to thrive. A river kept in its banks becomes very boring and will lack diversity.”
Paklaian added that the seasonal flooding plays an important role in the spread of native cottonwood trees.
"If the flooding ceases, cottonwoods will have difficulty regrowing, and the area becomes even more susceptible to invasion of other plants or trees," he explained. "There are lots of other benefits that stem from this, such as those to fish and wildlife. Certain bird species need complex and unbroken native trees for breeding and food. Native fish need complex in-stream habitat too. This is affected by factors such as alterations in water quality and/or temperature (water can be shaded by Russian olive infestations, causing cooling), but also the channelization reduces the complex habitat (aided by debris in the stream) that these fish need to thrive."
Crews scour not only river banks of the Escalante River but travel up washes in their search for Russian olive trees/Kurt Repanshek
Within Glen Canyon NRA, the Utah Conservation Corps crews that Engel leads have tackled the invasive trees across 1,549 acres, according to Paklaian. The goal is to reduce the cover of Russian olives to less than 5 percent of the landscape. The work involves both sawing down trees by hand and clipping out smaller saplings, and then spraying the stumps with an easy-to-see pink-tinted dose of Roundup, the commercial weed killer.
“We’ve covered 90 miles of the Escalante River, and there’s probably a couple hundred miles of tributaries that have all been treated,” he said. “That’s probably around 5,000 acres of treatment across the watershed.”
The treatments don’t take a one-and-done approach. Anyone who has cut down a tree in their yard, particularly aspen, knows about sucker shoots that soon appear. The same can happen with Russian olive, so Paklaian’s crews treat areas two or sometimes three times on five-year cycles. Plus seeds picked up by streams or birds can spread the trees downstream and even into previously treated areas.
“This is an issue and that’s why we do retreatment,” Engel said when I raised the possibility that seeds will simply resprout the invaders. “The seeds are only viable for three years or so, so by the second time we retreat there shouldn’t be any viable seeds. There really is no alternative about the seeds: we can’t pluck all the seeds off a tree and haul them to the dump.”
Attacking any Russian olive trees that survived the area’s first treatment was why we were standing on the banks of the Escalante River not far from Harris Wash, which flows down to the river from the popular Zebra slot canyon not far from the town of Escalante.
Engel, the restoration field supervisor for the Grand Staircase Escalante Partners, was leading a crew of three, each armed with a curved handsaw and 1.5-liter spray bottle of Roundup in the search.
“We use an herbicide with the active ingredient glyphosate. You just cut down the tree as low to the ground as you can, and put herbicide directly on the stump,” he said. “That’ll keep the tree from growing back. We have another technique where you can take a hatchet and cut into the tree and put herbicide into the cuts.”
Heading up an unnamed wash on the south side of the river, the group waded deep into the vegetation to attack Russian olive trees and saplings. The routine was repetitive: saw or clip the invader as close to the ground as possible, douse the trunk with Roundup, and move on. At times the crew would disappear within the bushy trees, only to reappear when the trees were toppled. My eyes searched for rattlesnakes and scorpions.
The next day we hiked upstream along the Escalante River a half-mile or so from camp to Harris Wash, where the crew turned around and began to work back down the river. One of the crew worked the riverbanks (sometimes while thigh-deep in the river), while the others split between the two sides of the river in their search.
Not far off in the distance we heard the bellowing of feral cattle – cows that long ago had vanished from their herds into the landscape’s geologic riddles. They’re another invasive species in the NRA that also needs to be removed; they’re an extremely skittish invader that doesn’t stand in place like the Russian olive waiting to be rounded up.
As Engel’s crew worked at their task, I came across some older, and quite dead, Russian olive trees that had been “frilled.” That’s a technique in which saws – chainsaws in this instance, or hatchets as Engel had explained – make cuts into the tree trunks that then are sprayed with Roundup.
"You cut down to the live tissue,” Jude DeVry, one of the Utah Conservation Corps volunteers, explained. “These types of trees regrow from their roots. It’s the roots you have to kill.”
With so many backcountry miles along the rivers and their numerous contributing washes and seeps to treat, it’s a daunting task for Grand Staircase Escalante Partners.
“It’s a remote landscape and it’s a challenging landscape, and there’s very little access other than on foot,” Paklaian told me during a break. “And so over those years it’s taken hundreds of people putting in hundreds of hours each and millions of dollars, really, to make it all happen.”
Glen Canyon National Recreation Area certainly seems to have its fill of invasive species, from the Russian olives and tamarisk trees along its river corridors and washes to the quagga mussels in Lake Powell. But the NRA is not the only unit across the National Park System that faces problems with invasive vegetation.
Across the park system, there’s an estimated 2 million acres being invaded by non-native vegetation. It’s a daunting problem, especially so when you add it to the threats non-native wildlife, feral wildlife, and non-native fish pose.
Traveler footnote: To learn more about Grand Staircase Escalante Partners and their work, visit www.gsenm.org.
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