Fence Meets Wall of Skepticism

But even the vehicle barriers, posts in the ground connected to each other by railroad ties, need year-round maintenance. The barriers at Organ Pipe have already been breached four times since they were completed this summer. A full-scale double fence in the Arizona desert, where summer rains cause flash floods that often rip up anything in their path, would be extremely costly to build, let alone maintain, Billings said.

The ecological effect of a fence would be significant, according to Roger Di Rosa, manager of the Cabeza Prieta National Wildlife Refuge in Arizona, which runs along about 50 miles of the Mexican border. Efforts to protect pronghorn sheep and encourage the jaguar to return to the United States could be seriously affected, he said. "If it doesn't fly, it's not getting across," he said. "The law is pretty straightforward but the border is very unique."

Marine Corps officers in the region also have questioned the need for a fence. Using a combination of vehicle barriers and ground-based radar, they had blocked a significant portion of smuggling traffic through their land on the Yuma Proving Ground, which runs along 30 miles of the border, Di Rosa and others said. In recent months, however, the Pentagon for unknown reasons ordered the base to install a fence. Marine Corps officers at the facility did not return a call seeking comment.

Di Rosa and others cited other potential unintended consequences of fence-building. In some regions along the border, the nearest main road can be 80 miles away. So to build the barrier, roads must be created. That could end up facilitating movement into the United States rather than blocking it. Officials along the border challenged optimistic timelines that the wall could be built in two years, citing the high probability of lawsuits from environmental agencies and land owners.

In Texas, which is to get 200 miles of fencing, opposition to the plan has come from law enforcement and city governments. The City of El Paso has officially opposed the plan, as has the Texas Border Sheriff's Association.

Maverick County Sheriff Tomas S. Herrera predicted ranchers would sue the federal government to fight the installation of a fence on their property. One reason is that ranchers want access to the Rio Grande, which snakes 1,254 miles along the border, to water their herds and for sport fishermen who pay to use the waterway.

Perhaps because of these objections, Congress, in a late-night concession just before adjournment, pledged that Native American tribes, members of Congress, governors and local leaders would get a say in "the exact placement" of any structure, and that Homeland Security Secretary Michael Chertoff has discretion to use alternatives "when fencing is ineffective or impractical."

Herrra thinks flexibility might be needed. He echoed a widespread skepticism about federal programs, hatched in Washington, designed to deal with the border problems.

"A few years ago, they installed cameras and said the cameras would solve things," he said. "Those cameras can pick up a tick on a cow's back. But when half the monitors are all busted like they are now, they don't work."

His prediction for how illegal immigrants would deal with the wall: "They will get ladders made out of mesquite and climb it."