For business and elected leaders in Texas border towns, it’s a simple question: Since arrests of illegal immigrants are declining steadily along the Texas-Mexico border, why should the controversial and costly fence be completed?

An analysis by the Texas Border Coalition, an association of elected officials and business leaders, shows a 56 percent drop in arrests during the last four years by the U.S. Border Patrol on the Texas-Mexico border. Government officials have maintained for years that fewer arrests mean fewer immigrants are trying to cross the border illegally.

The declining immigration arrests have revived the debate over the effectiveness of the planned fence because only a half-mile of the 110 miles of pedestrian fencing planned for the Texas border is finished. As government budget deficits soar, some question how fiscally prudent it is to build and maintain a project the Congressional Research Service estimates to cost $47 billion.

Eagle Pass Mayor Chad Foster, who heads the border coalition, said a steady increase of Border Patrol staffing is responsible for the declining arrests.

“We have a new Border Patrol station opened in Eagle Pass in the last six months, and the Border Patrol has continued to recruit agents,” Foster said. “I think because of their strong presence (on the border), that links back to reduced apprehensions.”

However, some experts maintain that a slowing economy is more responsible for the lower number of arrests. With fewer jobs available, fewer immigrants try to migrate north. That raises an obvious question: When the U.S. economy recovers, won’t more immigrants try to cross into America illegally, thus making a case for a border fence?

Foster, however, said by the time the economy bounces back Congress will have passed long-anticipated immigration reform that includes a guest worker program. Immigrant workers will cross the border lawfully through ports of entry.

His border group notes that in San Diego, where heavy fencing and walls have been in place for years, apprehensions are up 28 percent during the last four years.

“Here we are in middle of a financial crisis, and we’re going to spend billions on something that doesn’t make sense?” said Laredo Mayor Raul Salinas. “Walls don’t work - people go under, over and around them.”

Elected officials from nearly every Texas border town oppose the fence, saying it’s not as effective as more border agents and installing high-tech surveillance technology.

A U.S. Customs and Border Protection spokesman said that by mid-October, 210 of the 370 miles of planned pedestrian fencing and 153 of the 300 miles of vehicle barriers were finished, most of it in New Mexico, Arizona and California.

“Our operational analysis of the border has shown that fencing is a critical component of our border security strategy,” said CBP spokesman Michael Friel. “The Border Patrol has made the determination that fencing is needed in certain areas along our nation’s border.”

Friel said construction will pick up on the Texas border as the Dec. 31 deadline nears to complete all 670 miles of fencing mandated for the Southwest border by the Secure Fence Act of 2006.

He said it was “not logical” to suggest that areas with fencing have more border crossers.

According to Border Patrol statistics, apprehensions of illegal immigrants along the Southwest border have fallen dramatically in the last four years. In fiscal year 2005, nearly 1.2 million immigrants were arrested, dropping to 1 million in 2006 and 860,000 by 2007. In the first 11 months of the most recent fiscal year, which ended Sept. 30, arrests on the border had fallen to 660,000.

The head of a border agents union said fencing only delays illegal immigrants for the few minutes it takes them to climb over the barrier. If there are not enough agents in the area to detain them as they attempt to enter, they simply slip by.

“We don’t build fences that slice and dice people,” said T.J. Bonnner, president of the 14,000-member National Border Patrol Council. “We design fences that slow people down  and if you don’t have the agents in place, that’s all you’ve done.”

In the Rio Grande Valley, landowners who oppose the fence say the increased Border Patrol activity is all that’s needed.

“We have more bodies on the river and that is helping,” said Noel Benavides, a Roma City Council member who is fighting efforts to condemn portions of his family’s 140-acre ranch on the Rio Grande for the fence. “With the wall costing  millions per mile  how many agents would that hire?”

Bonner said immigration arrests are misleading because agents say two illegal immigrants make it across the border for every one who is detained.

He said the higher number of arrests in San Diego is related to moving agents to the Arizona border in reaction to a shift in trafficking routes.

“Tucson staffing has increased while the staffing in San Diego has decreased. That explains why (illegal immigrants are) going back to San Diego - because the odds of being caught in Tucson are higher,” Bonner said.

Opposition to the fence has been blunted in some border communities, where the government incorporated the barrier with needed projects.

In Hidalgo County, county and drainage district officials teamed up with the federal government and are rebuilding dirt levees on the river with 22 miles of concrete walls topped with security fencing. The $179 million project, funded in part with $48.5 million in local flood control funds, is on existing right-of-way and does not require land acquisition.

In Laredo, plans to fence miles of riverfront were scrapped when local Border Patrol officials determined it was not needed.

Instead of a fence, Border Patrol officials added hundreds of agents, are planning to clear thick stands of non-native cane that provides hiding places on the river bank and instituted a zero-tolerance arrest policy for first-time border crossers. As a result, arrests have dropped 23 percent in the last fiscal year.