The fight against the water-hoarding tamarisk

Brown and dying tamarisk trees along the Colorado River west of Moab, Utah. Courtesy the Tamarisk Coalition

The southwestern United States is defined by water, or more precisely, by its absence. Human settlers designed grand engineering projects to make the best use of what water was present, and today, water is captured behind massive dams and rerouted through concrete rivers. It’s used to build cities, grow rice, maintain green lawns and golf courses, and fill swimming pools and 500-foot fountains in Las Vegas casinos.

But scarcity has not been transformed into abundance; farmers, ranchers, states, and cities still fight over every drop. And so, amid the engineering marvels and hydraulic feats, a group of land managers is waging a campaign against an unlikely enemy: a water-sucking plant known as the tamarisk. To save a biome, we may have to kill one of its hardiest inhabitants.

The tamarisk, an invasive species introduced to the United States from Eurasia, is a deep-rooted plant that aggressively obtains water from the soil and groundwater. A single mature tree can produce up to 500,000 seeds per year, crowding out native plants along rivers and creeks and reducing wildlife habitat. The species now infests all the major rivers, springs, ditches, and wetlands in ten states—including Texas, Arizona, Utah, Colorado, New Mexico, Nevada, and California—and is rapidly expanding into others.

In the delicately dry ecosystems of the southwestern United States, that is a serious problem, adding up to over 800 billion gallons of lost water per year across the parched region. “That is equal to the water needs of 20 million people or one million acres of irrigated farmland,” said Tim Carlson, an environmental engineer and director of the Tamarisk Coalition, which aims to control the plant. 

For decades, land managers across the region have tried everything to get rid of tamarisks—cutting, burning, bulldozing, spraying herbicides, and unleashing hungry goats. It all failed. “We would remove it with backhoes and spray it with every chemical cocktail you could imagine and it always came back,” said Charlie Shannon, who manages the Orchard Mesa Wildlife Area in Grand Junction, Colorado, for the Bureau of Reclamation.

But hope, like weeds, springs eternal. Within the next two years, the Tamarisk Coalition hopes to remove all the tamarisks from the side canyons along a 25-mile stretch of the Colorado River. And one weekend in early December, I joined Carlson and a group of volunteers on a tamarisk control project in Devil’s Canyon, a rugged, sandstone canyon that empties into the Colorado River.

On the chilly morning, the other volunteers and I hiked into the snow-covered canyon armed with loppers, handsaws, and an impressive tool called a weed wrench, specially designed for pulling larger plants out by their roots. The group, which included 18 people, ranging from college students to retirees, was energized by the prospect of doing some serious tamarisk slaughtering. We made our way along the Devil’s Canyon trail lopping and sawing as we moved. In the spring, the Bureau of Land Management will follow up on the removal by spraying some of the new growth with herbicide in order to stress or kill the root system.

The fervor with which many in the West attack tamarisks may seem a bit strange. If the goal is a desert that’s more hospitable to life, why so zealously attack a plant that’s already proved itself hardy enough to survive—even thrive—in the harsh landscape? For most land managers, the removal of the tamarisk, an invasive species, is a righting of a natural order that has been upset. Land management is about maintaining a delicate balance, and that involves compromise. Some plants and animals have to be removed in order for others to flourish. In this case, land managers say, the tamarisk is being controlled to preserve limited water supplies and to bring back native plants, seen as the rightful inhabitants of western waterways.

Carlson suggested I take a look at an area where the battle against the tamarisk has been won, at least temporarily. So Shannon took me to Colorado’s Orchard Mesa Wildlife Area. There, the differences between where the tamarisk is and where it used to be are striking. The restored tamarisk-free areas are open, with clear views of the Colorado River. Sumac and cottonwood trees line the banks with native grasses, sedges, and shrubs covering the ground below. In contrast, where the banks haven’t been restored, the tamarisk thickets are so dense that we could not even see the river, much less walk to it.

What’s more, turkey and quail have returned to restored areas, Shannon said. As if to emphasize the benefits of restoration, a bald eagle soared nearby and came to rest at the top of a cottonwood.

“The real key is getting the native competition in that won’t allow tamarisk to come back: marshes, willows, bull rushes—plants with dense root mass,” said Shannon, as we surveyed some recently planted willows. “But that takes a lot of work and, most importantly, a lot of money.”

Or, perhaps a lot of tiny yellow and green beetles. Tamarisk beetles (Diorhabda elongata), native to the plant’s home range in China and Kazakhstan, have a voracious appetite for tamarisk and can thin even the densest thickets after a number of years. The beetles have been released in experimental sites across the West and have proven surprisingly successful.

Shannon plans to start using the beetles in 2007, and he is hopeful that they will make “one heck of a dent” in the remaining tamarisk population. “Tamarisk is never going to be completely removed, but the goal is to control it using the least amount of chemicals and money as possible. The bugs just might help us do that.”

No one knows what will replace tamarisks—native plants or another, perhaps nastier, invasive species. But western land managers are hopeful that they may be gaining the upper hand on one of many problems that plague the region. Carlson said that he has noticed the commitment to solving the tamarisk problem increase in recent years.

“One night, after I gave a presentation on tamarisk, an older gentleman came up to me and told me that he had earned his Eagle Scout rank by planting tamarisk to prevent soil erosion after the Dust Bowl era in the 1930s,” Carlson recalled. “He said he would gladly earn it again by helping me remove it.”

Originally published January 25, 2007


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