In 2012, cocaine in all its guises becomes unmarketable in the US after the drug control office treats the country’s water supply with a chemical to make the very thought of the white stuff unpalatable.

If this scenario happened, would it make any difference in the war on drugs? Many Mexicans believe their nation’s violent plight is a geographical accident: the misfortune of being sandwiched between the world’s biggest producers of cocaine and the largest market.

A cure-all may seem like a far-off scenario but cocaine use is already falling in America. It was the only recreational drug that lost users in the US in 2009. In 2008, less than a quarter of drug arrests were for cocaine or heroin. However, the UN estimated that more than six million people in North America used cocaine at least once in 2008. So far the fall in demand hasn’t helped Mexico.

Few savings on health and policing would be likely to materialise if cocaine consumption slumped. Drug users would shift to other products – some of them, such as speed, even more damaging to health. Police forces have lengthy backlogs of other drug offences to work on and would never consider laying off cops. The greatest benefit might be that some recreational users move to less addictive drugs. Currently 46 per cent of rehab clients in the US have a cocaine addiction.

Mexico’s infamously violent drug gangs would not disappear. Fortified with billions of dollars and vast human resources, they would diversify and produce methamphetamines and heroin while boosting their marijuana shipments well beyond the US.

Growers and processors in Colombia, Peru and Bolivia would also start planting more opium poppies, extending a trend that began with Colombian cultivation years earlier. They would search for new customers for their remaining output, pushing coca paste and crack smoking in the fast-growing markets of the Caribbean and West Africa.

The US government might be the surprise loser. The $500m (€352m) a year of mostly military aid it gives to Colombia is marketed as drug war funding, even if some believe the real goals include containing Venezuela’s regional ambitions and maintaining a military foothold in the continent. Without cocaine, planners would be left without a pretext for involvement in the area the US has long called its “backyard”.

Mexico has become a frontline in the turf wars over supplying America with cocaine, while shoot-outs in border towns such as Ciudad Juárez become almost daily occurrences. But if the US’s thirst for South American cocaine disappeared overnight, would cartels stop killing each other and violence dwindle – or would they simply move on to other organised crime?

Until the late 1980s, South American cocaine came to the US mainly through the Caribbean. Then law enforcement closed those transit routes, diverting the trade west, and Mexico became the primary line of passage. Today, the US Office of National Drug Control Policy estimates that 90 per cent of the hundreds of tonnes of cocaine that arrive in the US every year pass through Mexico, with each shipment enriching its drug cartels.

So what would happen if cocaine consumption disappeared? “Simple,” says Scott Stewart, a Mexico analyst with global intelligence company Stratfor. “Marijuana, black tar heroin and methamphetamine would continue to proliferate and the cartels would continue to profit off those.” Indeed, a recent dip in cocaine sales has been offset by a rise in methamphetamine production.

Mexican cartels earn up to $30bn (€21bn) a year selling drugs to Americans, but the drugs that can be produced inside the country, including marijuana, are cheaper to sell than cocaine, which has to be purchased from suppliers in the Andes, cutting profits. Still, cocaine represents a giant revenue stream – a kilo in the US can wholesale for $18,000 (€13,000) and retail for $150,000 – and its loss would make the cartels millions, if not billions, of dollars poorer. But the cartels have already moved far into other markets and other lucrative crimes. This latter shift is responsible for the terrifying wave of extortion, kidnapping, human smuggling and even intellectual piracy engulfing Mexico in violence. Not even the US giving up cocaine is enough to stop that.

Film: Pulp Fiction (1994) The first “indie” film to gross more that $100m in the US. Cocaine plots can go a long way when done right.
Music: Sir Elton John (1970s-80s) Sparkly and thin. Even if you think that might describe his music, it certainly wouldn’t describe the singer during his addiction.
Book: Fear and Loathing in Las Vegas (1971) Without decades of drug use, perhaps Hunter S Thompson couldn’t have written the closest literary equivalent to a Dalí painting.

While cocaine fuels the cycle of violence in Colombia – and funds armed groups – it remains just one of the country’s complex issues

If Americans were to give up their appetite for Colombian cocaine, experts believe that Colombia would be far less violent. In 2009, drug violence claimed the lives of nearly 16,000 Colombians. Of that total, 7,000 were gunned down by hitmen working for drug traffickers.

By how much drug crime would fall depends on Colombia’s largest rebel group, the Revolutionary Armed Forces of Colombia (Farc), which relies on the trade to fuel its coffers, and its ability to adapt and exploit new drugs markets.

“Whether levels of violence would significantly decline would depend on the capacity of the Farc and other armed groups to further open alternative drug consumer markets and the capacity they have to mobilise alternative income sources like kidnapping, extortion and arms trafficking,” says Silke Pfeiffer, director for Colombia and the Andes at the think-tank International Crisis Group.

Marxist rebels earn about $160m (€113m) a year from trafficking, supplying over 50 per cent of the world’s cocaine and 60 per cent of the cocaine entering the US. Most analysts agree the Farc would be significantly weakened if the lucrative market disappeared. But whether this would end one of the world’s longest-running and richest insurgent armies is debatable.