THE perimeter fence of the cocaine eradicators' makeshift camp in Pueblo Lindo, central Colombia, is ringed with watchful soldiers. The dawn air crackles with radio chatter and static from the lookout points and snipers.

At this end of the Rio Magdalena, Colombia's main river, the lagoons are tranquil. Flocks of herons and storks glide inches from the mirrored surface as the sun rises over the sierra, saturating the senses with light and sound as the jungle awakes. It's an idyllic spot - or it should be.

It's a three-hour ride in a dubious speedboat to Pueblo Lindo from Magangue, a transport hub where thousands of locals haggle over the price of cockerels, rum, illicit iguana eggs and nameless fruits as boatmen tout for trade. Along the river banks, mango vendors swarm to the dock as new customers arrive; it's a scene of benign tropical mayhem.

Floating midriver a human corpse drifts slowly past, a turkey buzzard pecking at the bloated stomach, and the mood shifts.

We're heading deeper into the backwaters, to Montecristo, a lawless place where narcotraffickers and cocaleros (coca farmers) once openly traded the gooey white pasta basica (basic paste) that is refined from coca leaves and sold as powder or crack cocaine on the streets of Europe and the USA. The town used to produce 10 tonnes of cocaine paste a year, which when refined yields around eight tonnes of pure cocaine hydrochloride, the sparkling powder that sells at around £50 a gramme in the UK.

The Colombian army is protecting 300 cocaine eradicators who are digging up the innocent-looking green bushes whose roots are tangled in the country's 40-year civil war. Guerillas and paramilitaries alike trade the drug for weapons or sell it to fund their campaigns.

The atmosphere is workmanlike and tense, as today the workers will head deeper and higher into the jungle slopes of the Sierra de San Lucas than before.

It's a four-hour slog to reach today's clandestine coca plantation. As we round a corner, a cry goes up. Anti-explosive dog handlers carry out a reconnaissance check of the field, checking for mines placed by guerillas or cocaleros protecting their crop, and once the all-clear is given, workers swarm across the two-hectare field, working in three-man teams.

It's risky work, as farmers have planted bombs alongside some crops - six workers were killed last year by one such device and the FARC gunned down 13 soldiers guarding the workers. In March, FARC guerrillas fired bombs made of domestic gas tanks from across the Ecuadorian border at the eradicators.

One digs out the roots, another wrenches the metre-high bush free and a third sprays herbicide around the area. In under two hours the field is stripped bare of coca. But down in Pueblo Lindo, Jorge Sanchez undoes all their work with a smile and a gentle shrug.

"As soon as they are gone, I'll be planting more coca. I'd like to grow coffee, sure, but that takes seven years. This bush grows back in nine months, and produces leaves every 60 days," he says. "Rice sells at $25 a hundredweight, takes five months of hard work, and I need to transport it by river. That costs a lot. Coca paste goes for $1500 a kilo and the plant needs no attention. What would you do?"

Many rural communities are penned in between entrenched poverty, the US-funded anti-drugs programme Plan Colombia which wipes out their illegal crops and leftist guerillas and right-wing armed groups and narcotraffickers who sometimes force them to grow coca. With poor infrastructure, few roads and no external market for their goods, the farmers often have no practical or economic choice other than coca cultivation to survive.

"We're not bad people, we'd like to live legally. But we need support. We've been living off this bush for years," says Sanchez.

The Revolutionary Armed Forces of Colombia, or FARC as they are known in Spanish, were originally a peasant army formed in the 1960s dedicated to a Marxist overthrow of the Colombian state. Colombia sees a massive gap between rich and poor, and social mobility has been virtually non-existent for much of the last century. The guerrillas took control in the 1970s and 1980s, and waged war on the Colombian government for much of the last 40 years.

However, the guerrillas' leftist philosophy has been compromised and almost abandoned in the last two decades, as it swapped drugs for arms and forced peasants to grow coca. It has also lost the support of many thanks to its policy of kidnapping, murder and extortion.

Some say they are losing influence. One FARC leader, Raul Reyes, was killed in a cross-border raid into Ecuador by Colombia last month, leading to a brief regional crisis that threatened war. Ecuador says Colombia must do more to contain its civil war; Colombia says Ecuador must stop sheltering the guerilla.

In March, a leading FARC commander, Ivan Rios, was murdered by one of his own soldiers, who cut off his commander's hand and delivered it to the Colombian police in order to prove the identity of the dead man. He is to receive a six-figure reward from the government for his treachery.

While many have presented FARC as a diminishing force in the conflict, it is wrong to underestimate their reach. Figures vary, but some reports suggest FARC rebels number 18-24,000, and many Colombians are still joining their ranks as an escape route from poverty.

In response to the Marxist guerilla through the 1980s and 1990s, many wealthy landowners contracted brutal private armies to defend their land. These paramilitaries are heavily involved in the cocaine trade. Many thousands of their number have demobilised in recent years under controversial legislation that many observers say has been too lenient, with short jail terms offered for confessions of massacres. But they are active in the drug trafficking and many formed gangs.

Colombia's civil conflict has little political basis, and is better seen as a narco-war, says Professor Rodrigo Losada, a security analyst at Bogota's Javeriana University.

"The armed actors in the Colombian civil conflict have systematically used the cocaine industry to further their warlike aims," he said. "If it wasn't for cocaine, the FARC could never have formed a 24,000-man strong army, all perfectly armed and equipped. The paramilitaries, for their part, have also been able to amass a force equal to the FARC through the coca trade, whether through planting, protection rackets or by taxing the flow of cocaine through Colombia's rivers and airspace. The impact of cocaine profits on the power of the armed groups' ability to act has been overwhelming. This has also had serious implications for the political life of the country too, with congressmen bought or threatened by narcotraffickers."

President Alvaro Uribe is a staunch proponent of military force against the FARC, a stance partially explained by the murder of his father by the guerilla in a botched kidnapping attempt. Domestically, Uribe is popular for his hardline anti-FARC policies in Colombia, with an 83% approval rating in a Gallup poll last month. He has beaten the guerilla back into the jungle, freeing up Colombia's main cities from the threat of violence.

While the US has paid billions in military aid and anti-drug spraying planes - Colombia is the third-biggest recipient of US military aid in the world - the task is Sisyphean. New coca bushes are planted before the leaves of the sprayed crops wither, experts say. In Europe and the US, demand has risen, use is up and purity has improved.

Colombia, a key US ally in an increasingly leftist Latin America, is the world's biggest producer of cocaine, weighing in with 600 tonnes a year, 62% of global supply. The US has advocated the aerial fumigation of coca crops with herbicides, from small planes flying low. But this method of eradication is scattergun at best, and inefficient, dangerous - and possibly illegal - at worst.

On March 31, Ecuador launched a criminal case against Colombia in the international court at the Hague over anti-drug fumigation, alleging that herbicide clouds drifting from the planes is damaging food crops in Ecuador.

Last year President Alvaro Uribe admitted fumigation was flawed after farmers said legal crops were wiped out by the spray, and proposed manual eradication as a more permanent solution. In tandem with the groundwork, technical and financial assistance would be offered to cocaleros to help them replant their fields with lucrative crops. It would also create jobs and boost state control of rebel-held areas, it was claimed.

Uribe, a right-wing hardliner, has shifted strategy towards a manual cocaine eradication programme in favour of the aerial attacks, although 320,000 acres of land is still sprayed. Colombia says it will eradicate almost 250,000 acres of coca by hand this year.

But the real drivers in the shift to manual eradication are US Democrats, who have been critical of aerial spraying, citing environmental concerns. They demanded a cut in favor of alternative crop schemes to help the cocaleros make the transition to legal work.

But the programme has met with massive protests by peasants in coca strongholds such as Taraza in the Antioquia province. In February, 2000 farmers clashed with police, blocking roads into the province's main city, Medellin, throwing stones and burning down a toll booth. They returned to their fields after the government paid them $80 to go home, and offered alternative crop development programmes.

Here in listless Pueblo Lindo, though, there is no such help on offer, and the entire town looks hungry.

Acting in isolation in its attempts to control a supply chain that runs from the Andes to the nightclubs and bars of Glasgow and London, it seems that the best the Colombian government, acting can hope only for partial success.

"To resolve this problem means that the cocaine-consuming countries, the EU and Europe, need to renounce their repressive anti-drug policies which allow drug trade to be legalised in some controlled way," says Professor Losada.

Rodolfo Llinas, of the United Nations Office on Drugs and Crime in Bogota, agrees. "We think that maybe we can have a solution in the short term, but the coca crops will move to another country - if demand exists, supply will exist. The countries that consume the cocaine need to propose solutions too," he says.

"To convince the cocaleros to abandon the crop is not only a matter of alternative developments. Its also a matter of building market and giving safety as many of them are forced to grow coca. It's a complex matter that cannot be fixed with just one approach," he says.

"I'd do anything rather than grow coca," says one farmer in Montecristo who preferred not to be named. "I could go to jail for it now. But my wife is sick and pregnant, and there is no other industry here, and we haven't planted regular crops for years."

It seems that neither the Colombian government, the army, the eradicators nor any one of the cocaine users in Europe or the US has an answer for him.