CIUDAD JUAREZ, Mexico (Reuters) - Mexicans overwhelmingly say they oppose the wall U.S. President-elect Donald Trump has promised to build along their northern border.

A general view shows a newly built section of the U.S.-Mexico border wall at Sunland Park, U.S. opposite the Mexican border city of Ciudad Juarez, Mexico, November 9, 2016. Picture taken from the Mexico side of the U.S.-Mexico border. REUTERS/Jose Luis Gonzalez

But in Mexico’s Ciudad Juarez, where extensive fencing was erected by the United States to secure the border between 2007 and 2010, residents have a more nuanced view of what a wall can mean. They say the Juarez fence has both caused and relieved problems in the city and nearby areas.

Some say the barrier has made life in Juarez better, diverting drug and human traffickers to more remote spots where crossing the border is easier. Others say the high fence bred a new kind of crime in the city, encouraging drug dealers who find it harder to get wares across the border to divert some of their product to expanding and serving a local market.

Juarez’s newly elected mayor, Armando Cabada, sees both sides. He says the fencing, cameras, sensors and stricter controls on border bridges have stopped flagrant crossings of undocumented Mexican migrants into downtown El Paso, Texas, which sits just across the fortified border, in sight of his wood-panelled office.

On balance, however, the negatives have outweighed the positives, he says. He notes that shortly after the wall was built, Juarez was plunged into a hellish war between cartels that made it the murder capital of the world, while El Paso remained the safest U.S. city of its size.

After the border got tighter, Cabada said, “the narco traffickers had to battle much harder to cross their drugs into the United States, and a lot ended up staying here.”

The increased local supply of drugs changed social dynamics in the city and addiction and petty crime soared, he said.

It is hard to isolate causes of the chaos that engulfed Juarez in 2008 when the Sinaloa and Juarez cartels fought over trafficking routes, but the belief that tighter controls contributed to the city’s deadly, downward spiral is widespread among business leaders, security officials and politicians consulted by Reuters.

The city of 1.4 million saw murders rise from 336 in 2007 when work on the fence began, to 3,057 in 2010 when the work was mostly concluded. Only two people were murdered in El Paso in 2010, down from eight in 2006.

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Last year murders were back below 2007 levels and normal life has begun to return, but strong demand for methamphetamines in Juarez has triggered a local turf battle and a new spike in violence, Cabada and city security officials said.

Drug use in Juarez is among the highest in Mexico, government health surveys show.

‘LESS CHAOS’

A poll conducted in May by Baselice & Associates Inc for Cronkite News and other media groups spoke to 1,500 people in 14 border cities in Mexico and the United States. It found that 72 percent of respondents on the U.S. side and 86 percent on the Mexican side said they were opposed to building a wall.

Esteban Sabedra, a factory worker living in working class Anapra, on the western fringe of Juarez, is among the minority of Mexicans who would like to see more secure fencing.

Sabedra’s home is a city block away from a rusting, low wire fence in place since the 1980s separating Juarez and El Paso, that the U.S. Customs and Border Protection is now replacing with 1.3 miles (2.0 km) of 15-foot-high steel bollard barricade.

He welcomes the new structure, saying he hopes it will deter human and drug traffickers who currently ply the neighborhood and intimidate residents.

“(This new fence) is not a problem for us, on the contrary, it’s better, less people will move through here,” said Sabedra, who earns 150 pesos ($7.28) per day making brake pads for the U.S. market at a Juarez assembly plant. “There will be less chaos.”

Indeed, experts say fencing around El Paso is one of the factors behind a sharp drop in U.S. border guard apprehensions in the sector, to 14,495 last year from 122,256 in 2006, a drop partially attributed to illegal migrants shifting routes to less protected stretches of border.

Migrant flows are a fraction of what they were in the sector largely because of the greatly increased security presence including the fencing and a near doubling of border agents, the Washington Office on Latin America rights group said in an October report.

DERELICT HOMES, SPAS

Ciudad Juarez’s public prosecutor, Jorge Arnaldo Nava López, blames the El Paso fencing for contributing to a sharp uptick in crime along a fertile strip through the desert known as Valle de Juarez. The crime spike has been particularly acute where the barrier ends near Guadalupe municipality.

“It has fostered a displacement towards the villages on the outskirts of Ciudad Juarez,” Nava said.

Valle de Juarez used to be a popular weekend escape for the city’s middle class. Now, brutalized by violence and abandoned by outgunned municipal police, many of its spas, holiday homes and cotton farms lie derelict.

Officials and migrants say Mexicans and Central Americans pay gang members hundreds of dollars to wade across a sluggish stretch of the river and try their luck dodging border guards to reach the towns of Tornillo and Fabens on the other side.

Fortification of the border could push the chaos elsewhere. But Nava, who previously headed Chihuahua state’s anti-kidnapping agency, fears it could also spark blowback in the form of increased extortion and kidnapping if local gangs now dedicated to drug trafficking are frustrated by a new wall.

“We are not exempt from the possibility that this kind of crime flares up, and that (more) drugs intended for the United States begin to stay here in Ciudad Juarez,” said Nava.