Only a few steps north of the barbed-wire fence that separates the Buenos Aires National Wildlife Refuge from Mexico is a chain of steel sawhorses that could help save a park trampled by illicit visitors and littered with trash and rusting vehicles.

Made of century-old railroad tracks, the waist-high vehicle barrier won't completely block the thousands of illegal immigrants who cross into the refuge on foot each year. However, it is impassable to the vehicles that wreak the worst environmental damage as smugglers tear across the grassland.

"We love it," refuge manager Mitch Ellis said as he surveyed the rusty barricade for the first time last week. "The wall is a whole different story."

For now, barriers are the best compromise available for land managers who want to protect their battered parks, Border Patrol agents who want to keep illegal immigrants out and environmentalists who are concerned that solid border walls will destroy protected spaces and impede animal migration.

They are proving effective, too, reducing illegal vehicle traffic by more than 90 percent in some areas. More barriers are planned for other federal and natural areas overwhelmed in recent years by migrant traffic. Eventually, officials said, most of Arizona's border with Mexico will be lined with the barriers.



Barrier beginnings

Tighter immigration enforcement in San Diego and El Paso in the 1990s squeezed illegal immigration into the harsh Sonoran Desert, sending hundreds of thousands of people into the national parks, forests and wildlife refuges along the Arizona-Mexico border, the busiest area in the country for immigrants.

More than 85 percent of the land directly on the border and more than 60 percent of the land within 100 miles of the border are federal lands.

In July, Organ Pipe Cactus National Monument completed a million vehicle barrier along its 30-mile border with Mexico. In the weeks since it was finished, park personnel have seen an estimated 95 percent decrease in illegal vehicles, Superintendent Kathy Billings said.

At Buenos Aires National Wildlife Refuge, the preserve's 5.5-mile border with Mexico will be lined with vehicle barriers within one year. Cabeza Prieta National Wildlife Refuge also plans to install them. Eventually, vehicle barriers will be placed all along the 262-mile stretch of the border monitored by the Tucson sector of the Border Patrol, including on the Tohono O'odham Reservation, said spokesman Jesus Rodriguez. He didn't know when they would go up or how much they will cost.

"The refuges on the Southwest border right now really are under siege," Ellis said. "That barrier down there will help us protect our habitat."



Buenos Aires' problems

The problems facing the 118,000-acre Buenos Aires refuge are typical of those at public lands along the border.

More than 250,000 illegal immigrants entered the refuge in 2004 and 2005 alone. Foot and vehicle traffic have cut more than 1,300 miles of illegal trails through the native grassland, some of which could take more than a century to recover. Abandoned cars and tons of trash litter the preserve, which was purchased in 1985 as a refuge for masked bobwhite quail.

Vehicles have caused much of the damage. Stolen vehicles speed back and forth across the border through holes cut in the barbed-wire fence. Drug and human smugglers lead Border Patrol and federal law enforcement officials on off-road chases that devastate native plant and animal life.

About half of the refuge's .5 million annual budget is spent on border issues, including fence repair, abandoned vehicle towing, stolen property, trash removal and salaries of staff working on security or Border Patrol coordination instead of environmental issues, Ellis said. If that keeps up, the refuge may soon have to cut public programs.

"We've already talked about the possibility of closing some areas to the public" because of security concerns and lack of money to maintain them, he said. About one-third of Organ Pipe is closed to the public because of security worries.



Helping environment



Immigration enforcement in the parks and preserves has sometimes been at odds with environmental protection whether it's off-road vehicle patrols on fragile desert landscape or floodlights disrupting wildlife's nighttime behavior.

Vehicle barriers, however, seem to be an answer to one point on which environmentalists and Border Patrol agree: The success of a border wall in Arizona's public lands is doubtful.

"If we don't have the infrastructure or technology to back up that fence, what good does that do?" said Gustavo Soto, spokesman for the Border Patrol's Tucson sector. "That's not going to happen."

On Aug. 2, the Senate voted to spend .8 billion on 370 miles of triple-layer fencing and another 460 miles of vehicle barriers along the Mexican border. But the bill has been bogged down in negotiations.

Supporters of walled fences say they have been successful in helping to regenerate environments eroded by immigration traffic.

In Arizona, environmental groups reacted furiously to the Senate's proposal, pointing out that solid fencing could crush native plant and animal life and block endangered species' migration.

"The only things these walls are really going to block is wildlife," said Daniel Patterson, desert ecologist at the Tucson-based Center for Biological Diversity.

Vehicle barriers are environmentally neutral, allowing migrating animals to pass back and forth. The only animals they will block are Mexican ranchers' cattle, which wander through holes in the barbed-wire fence and graze illegally on the Buenos Aires refuge. As he drove away from the border, Ellis pointed out a tan-colored border-crossing bovine blithely chewing grass.

"There's an illegal immigrant," he quipped.

New fences protecting fragile areas on border