Invasive plants are slurping up precious water in drought-stricken southwest Colorado
This story was originally published by The Colorado Sun.
When Dolly Gardner bought her land in Montezuma County in the southwestern corner of Colorado in 1970, there weren’t any Russian olives on it. Now, the invasive species has taken over.
“It looks like it is a forest,” Gardner said. “We used to have kind of a wetland, but they take all the water and therefore we don’t have as much pasture.”
Gardner is among the many Colorado landowners grappling with plants that were brought for ornamentation but have since become a nuisance across the state.
The federal government introduced nonnative plants across the West decades ago to try to prevent erosion and serve as windbreakers. Now, Montezuma County officials are hunting for ways to uproot the nonnative invaders, from offering to defray landowners’ removal costs to seeking a long-term federal grant to bolster plant removal.
The county has the support of U.S. Rep. Lauren Boebert, R-Rifle, who has agreed to help. She expressed her support for the department’s grant application to remove nonnative species and made an appropriations request for federal funding in support of noxious weed reduction efforts designed to combat drought.“The federal government brought the Russian olive and salt cedars to Western states,” and now it needs to provide the funding to save these lands, Boebert said in a news release.
Drier and saltier soil
Russian olives, salt cedars (also called tamarisk) and other invasive species suck up water on about 8,000 acres of land in Montezuma County. The consequences range from trouble growing crops and raising livestock to increased wildfire threat. In regions hit hard by this year’s drought, the growing population of noxious weeds is causing more of a problem than ever.
“They get the lion’s share of the water,” Gardner said.
Salt cedars and Russian olives aren’t listed as noxious weeds by the federal government. It has prohibited the sale and planting of the species in only a patchwork of states, which includes Colorado.
Bonnie Loving, program director of the Montezuma County Noxious Weed Department, said there are two nonnative species that stand out among the more than 30 that they manage.
“We’ve definitely ranked Russian olives and salt cedars as being two of our priority species because we see the impacts they’re causing and just how fast their populations are exploding,” Loving said.
Russian olives and salt cedars consume at least 1.6 acre-feet of water per acre per year. Salt cedars guzzle dozens of gallons of water per day, especially during summer months. Estimates range from about 32 gallons of water per day for an average sized tamarisk, according to the 2007 U.S. Geological Survey, to as high as 200 gallons daily for a larger tree.
These species became prominent in Montezuma County in the 1990s. The problem remained under the radar until recently. Loving said it could take 20 years to restore the land.
The roots of salt cedars reach deep into the ground and pull up salt into their leaves. When those leaves drop to the ground, the soil becomes extra salty.
Loving said most native species can’t tolerate high salt levels in the soil, causing them to die. Salt can also increase soil erosion and contaminate the soil in the long-term.
“With our drought, we realized that we really need to attack it now,” Loving said. “We’re losing so much water and the salinity issues are so severe on our soil health.”
Increased salt levels in the soil aren’t just a problem in the counties with noxious weeds. The leaves of the salt cedars can get into the waterways and impact other communities down the river.
“Anybody who uses that water downstream as irrigation on their property, it still has that salt in it,” Loving said. “It’s gonna contaminate their soil and it’s going to kill their crops.”
Help defraying costs of removal
Montezuma County has a cost-share program to pay for removal of the species on private property. Landowners pay a certain amount per hour and the county covers the rest of the costs.
“Largely throughout the Colorado River Basin, people simply can’t afford to remove them on their own,” said County Administrator Shak Powers.
The removal process depends on the size of the plant. For bigger trees, a chainsaw is used, followed by herbicide on the stump that will hopefully kill the rest of the root system. For smaller trees, an excavator with a mulcher attachment does the trick.
Follow-up herbicide must be reapplied to prevent new plants from sprouting. This step of the process — adding pesticides because cutting alone is not enough to kill the roots of a larger plant — looks similar to kudzu removal in North Carolina. Depending on the area, the department will restore native species to the land to try to prevent more noxious weeds from taking over.
Biological control, or using natural means to kill unwanted plants, such as introducing insects that feed on them, can be an effective tool to slow the spread of salt cedars, especially in remote areas. But Loving said the tamarisk beetles are not enough for longer-term eradication. Sprout treatments and reseeding are still needed to stop the invasive plants from coming back. The county wants to restore native and desirable species, so removal would still be necessary after the beetles move through an area.
Two major challenges complicate the removal process: a lack of mapping and a lack of funding.
Loving said her department lacks the resources to prioritize mapping nonnative species. She said accurate mapping from county managers would help track the magnitude of the problem to understand where the species are located and whether the situation is improving.
Long-term federal funding is another necessity for Loving. Federal funding would offset the cost of removal and follow-up treatment for landowners, many of whom remember when the government gave them these plants for their property in the first place.
“The biggest thing is we don’t want to put a burden on the landowners,” Loving said. “It is pretty expensive.”