As conservative voices in the United States clamor for even tighter security along the Mexican border, a new study concludes that any further upsurge of forces would be counterproductive.

In a report titled “Beyond the Border Buildup: Security and Migrants along the US-Mexico Border,” the Washington Office on Latin America (WOLA) and Mexico’s College of the Northern Border (COLEF), found that further buildup of the Border Patrol would yield “diminishing returns.”

“A closer look at the border reveals that after a historic buildup of the US security presence there, further increases in money, barriers and manpower are unnecessary,” according to the report.

Urging Washington to reassess its border policy, the report called on the government to “view the border security buildup as a past policy, not a direction for the present or future.”

Conservatives in the United States have been calling for reinforced security along the border, and have insisted more Border Patrol personnel are necessary. Added to this are calls to complete the construction of the fence that demarcates much of the 3,200 kilometer border, and even electrify the barrier to prevent illegal migrants from crossing into the United States. Fears in Arizona about Mexican cartel violence spilling into the US have led to a proposal for a new border militia.

“The facts contradict the call to escalate security along the border,” said Adam Isacson, WOLA analyst and the study’s co-author. “The whirlwind security buildup should stop now,” said Isacson.

The buildup, which started two decades ago at a gradual pace, surged after the September 11, 2001 attacks in New York and Washington. It is aimed at stemming illegal immigration and drug trafficking, while trying to prevent the drug-fueled violence that has wracked Mexico from crossing into the US.

The surge in border control has come at the hands of the Drug Enforcement Administration (DEA), the Federal Bureau of Investigation (FBI), the Department of Homeland Security (DHS), and its sub agencies, as well as the Defense Department, which has deployed troops as back-up to the Border Patrol, and to collect intelligence. The Pentagon has been flying reconnaissance drones on both sides of the border. National Guard troops have also been deployed.

Border agents have indeed seen an increase in drug seizures in recent years. Between 2005 and 2010, southwest border seizures of marijuana increased by 49 percent, methamphetamine by 54 percent, heroin by 297 percent and MDMA (ecstasy) by 839 percent, the report says. By contrast cocaine seizures have dropped 21 percent.

Though the number of illegal migrants crossing the border is nearly impossible to estimate, apprehensions by the Border Patrol have fallen by 61 percent since 2005.

But the report says the drop in border crossings can only partially be attributed to tighter security. The economic crunch in the United States since 2008 has driven many migrants back home, and those who haven’t left are staying put. Another factor is the increasingly risky journey faced by migrants travelling through Mexico to the US. Greater control exercised by drug traffickers on the Mexican side along smuggling routes add to the risks.

“The dangerous gauntlet of abuses at the hands of criminal organizations — and certain Mexican officials — through which migrants must pass on the way to Mexico’s northern border causes some to reconsider the journey,” according to the report. Some 20,000 migrants, mostly from Central America, are kidnapped every year and countless others are subject to extortion, sexual assault and other abuses, sometimes with the complicity of corrupt Mexican officials.

At the same time, the feared spillover into the United States of Mexico’s drug-related violence, which has claimed 50,000 lives in the past six years, has not materialized, according to the report. In 2010, El Paso, Texas, across the border from Ciudad Juarez, had the lowest homicide rate of all US cities, with a population of more than 500,000. That same year Ciudad Juarez had one of the highest — if not the the highest — homicide rate in the world at 283 homicides per 100,000 people.

One reason that violence is not spilling over, the study’s authors found, was that Mexican trafficking organizations try to avoid any incident on the US side that could trigger a closure of official border crossings, through which most drugs pass.

The report concludes: “The present moment — marked by flattening budgets, plummeting migration, and new presidential terms about to begin in both countries — offers a golden opportunity to pause and reconsider.”