It probably seemed like a good idea at the time, but the early 20th century decision to plant salt cedar to stabilize stream banks in the Southwest guaranteed diminished flow of the rivers and tributaries vital to the agricultural, environmental and economic stability of the region.
Today, scientists from New Mexico and Texas universities, as well as various state agencies, are spending millions of dollars to eradicate the aggressive, invasive species from the Pecos and Rio Grande river basins.
“We've been testing methods to get rid of salt cedar since 1987,” says Keith Duncan, a brush and weed control specialist with the New Mexico State University Cooperative Extension Service. Duncan works out of the Agricultural Science Center in Artesia in the heart of the Pecos Valley.
Duncan expects results. “We sprayed a large demonstration project in 1995 and 1996 to show what we could do,” Duncan says. “Most efforts since then are results of that initial program.”
The breakthrough came with a herbicide, Arsenal, a broad-spectrum material from BASF that is “environmentally sound and the only one that works on salt cedar,” Duncan says.
Cutting the trees has been ineffective. “The vegetation is so aggressive it grows back from the trunk or the roots. It's also time-consuming and expensive to take out as many trees as we need to.”
Initial spraying projects have included relatively short stretches of the river basins, but Duncan says an effective project must include the entire courses of the Pecos and Rio Grande rivers as well as tributaries.
It's time to get started, he says. “Salt cedar is a major factor in low water levels in both these rivers. Studies show that removing salt cedar will improve both quantity and quality of water. Springs come back, steam flow increases, and wetlands return.”
Duncan says the exotic species has no native enemies and thrives in the arid Southwestern climate. “Along the Pecos, stands of salt cedar will reach 3,000 to 4,000 per acre. Cottonwood and willow populations, by comparison, will be nearer 200 per acre.”
One salt cedar is a giant straw, sucking as much as 200 gallons of water per day out of rivers, springs and wetlands. “When we remove the salt cedar, water begins to come back.
“But success demands a major program. We'll need at least two years to measure kill from the herbicide.”
Duncan expects a $5 million project to begin this fall, $2.5 million for the Pecos and $2.5 million for the Rio Grande. “We have not initiated a major program up and down the river basins before,” he says. “It's a complex water system and we have to treat major acreage to have an impact. We'll start this year, but we have to treat a lot of miles of the river.”
They will apply herbicide by helicopter because of increased control compared to fixed-wing aerial application. Spray area could include up to a 200-foot swath along the river basins. Some areas may require less, depending on how far from the river salt cedar has spread, as well as what vegetation, cropland or sensitive areas might be along the riverbanks.
Duncan says Arsenal has provided up to 90 percent control of salt cedar in early demonstrations. “But we'll be working a larger area and we'll encounter more variables.”
One problem the project has not encountered so far is strong opposition from environmental organizations.
“Most environmentalists are behind us,” Duncan says. “They understand that something has to be done. Salt cedar is not good for wildlife, fish or native vegetation. They understand that a herbicide is a tool we can use in the right place for an environmental benefit. We all want to assure safeguards.”
Duncan says the Audubon Society, the Sierra Club and other groups have supported the effort.
The herbicide is a big reason for the support. Arsenal began as a specialty product to control roadside and right-of-way vegetation.
“It's a broad spectrum herbicide that will kill a lot of plants,” Duncan says, “but not everything. It's not effective on legumes. We'll have to be careful around willows and cottonwoods, too.
“But the herbicide label includes a habitat improvement statement and is the only one used for endangered species habitat improvement.”
Still, Duncan says some sensitive areas will require other measures. “Where we find susceptible crops and trees, we'll have to cut out the salt cedar.”
Duncan says herbicide application “is no silver bullet. It's just part of the solution. We still need rain and snow pack to restore stream flow in these rivers.
“In New Mexico, we need to define adequate water rights. Improved irrigation efficiency is part of the solution as well.”
Duncan says if the region gets back to more normal rainfall and snow-pack patterns, eradication efforts will become evident.
“We could see a difference in stream flow within two years,” he says. “If drought conditions persist, we'll still be in trouble.”
If the project is carried out all the way down the river basins, and if weather improves. and if legislators get behind the project, “we'll see tremendous improvement in five years,” Duncan says. “But that's a lot of ifs.”
Climate and politics, he says, are equally difficult to predict. “But politicians have begun to realize how important water is to the region. They understand that our rivers are in trouble. The Pecos is in critical condition. The Rio Grande and the Canadian are getting critical. Other rivers face similar problems. That's why politicians are beginning to pay attention to salt cedar.”
Duncan says this project will not get rid of every salt cedar stand along the river basins. “But we can get the population down to where native vegetation and the natural ecosystem can function again.”