The soldiers — with their skinny leaves and nonnutritious seeds — have invaded more than 1 million acres of river and stream banks in New Mexico, Texas, and more than a dozen other arid states. They have pushed out native plants, birds, and other wildlife and sucked dry already dwindling water supplies.

"This is public enemy No. 1 as far as I'm concerned," said Corky Herkenhoff, who farms about 600 acres along the Rio Grande. "It's unbelievable the amount of water it consumes, and it renders the land pretty much useless."

One of the most important steps in destroying salt cedar is reintroducing native plants. But scientists are finding that easier said than done.

Along the Green and Colorado rivers in southeastern Utah, dense stands of salt cedar stymie rafters trying to beach their boats. "You can see beaches that look like they have a lawn on them, a really green carpet," said Darren Vaughan, co-owner of Tex's Riverways in Moab, Utah. "When you get closer, you notice that they are baby tamarisk, tens of thousands of them."

Water and land managers across the West have been trying for decades to stop the rapid growth of salt cedars, first introduced in the United States from southeast Asia more than a century ago. "It takes a lot of work and persistence regardless of the method that you're trying to use," said Keith Duncan, a weed and shrub specialist with New Mexico State University's Cooperative Extension Service.

The most common tools are bulldozers, herbicides, root rakes, and fire. Researchers are also testing a biological agent: the Chinese leaf beetle. At Herkenhoff's farm in Socorro County, a bulldozer equipped with a giant rake has been busy pushing over salt cedars on a parcel of land south of his home. The snapping and crackling of branches could be heard over the roar of the bulldozer's engine as it plowed into a seemingly impenetrable stand of the pink-tipped trees.

Along the Rio Grande at Bosque del Apache National Wildlife Refuge in central New Mexico, managers have worked for 15 years to control salt cedar. The refuge is a pit stop each winter for thousands of migratory birds.

Salt cedars soak up one-third more water than native plants and offer little for wildlife. "There is structure in a native habitat. There's a ground layer, shrub layer, and canopy," said John Taylor, a U.S. Fish and Wildlife biologist at the refuge. "Salt cedar thickets are one block. You almost have to crawl on your belly to get through them."

Refuge managers constantly work to convert nonnative vegetation into more suitable habitat. "We try to replicate the historic mosaic of what once occurred in the valley here," Taylor said. "You might have seen wetlands, meadows, a brushy area of scrubby mesquite, or salt bush."

The Middle Rio Grande Conservancy District is also trying to restore native habitat along the river from Cochiti to Socorro, but the makeup of the bosque creates an obstacle. Salt cedars are intertwined with native trees, making for a thick stew of vegetation.

Salt cedar grows along the banks of the Animas and La Plata rivers in northwestern New Mexico and along the Canadian River in the northeast. Southern Canada, Montana, and North Dakota have groves of the troublesome trees. "Every western state has it, and the drier the state, in general, the more worse off that state is," Duncan said.

One of the main problems with salt cedar is its unquenchable thirst. A large salt cedar can absorb 200 gallons of water a day, making it a handy scapegoat for the severe drought that grips New Mexico.

But Tom Davis, manager of the Carlsbad Irrigation District, said it's not that simple. "There's plenty of people out there saying, 'It's salt cedar. You kill that salt cedar and you'll have enough water,'" he said. "It's not so. There's no silver bullet, no panacea" to solve the drought.

Quantifying water savings from the eradicating salt cedar is difficult, Davis said. As part of the Pecos River Restoration Project, 5,000 acres of salt cedar were cleared to see what would happen to the water table. Native seeds have been slow to take root, and the water table remains unchanged.

"The drought has an impact, that little strip of vegetation along the river bank has an impact, shallow groundwater wells being pumped in the farming area immediately outside the flood plain has an impact," Davis said. With all the variables, he said, it can't be assumed that getting rid of salt cedar will provide enough water to meet everyone's demands.

Still, the battle to clear salt cedar continues. Researchers over the last three years have used herbicide to douse salt cedars along 118 miles of the Pecos River in West Texas. Preliminary results show a potential water savings of at least 6,380 acre-feet per year for the treated area. An acre-foot, about 326,000 gallons, can meet the annual water needs of one to two U.S. households.

At Bosque del Apache, biologists estimate they could save 6,000 acre-feet of water each year by getting rid of salt cedar. Workers have been busy cutting salt cedars down to their stumps, spraying them with herbicide to keep them from sprouting, and replacing them with native plants. The job can be difficult because salt cedars produce tens of thousands of seeds from spring into early fall that are carried for miles by wind and water.