Eradication efforts elsewhere have pushed coca cultivation into rural El Rosario, where workers processed coca leaves recently.

PASTO, Col****ia Along with Col****ias successes in fighting leftist rebels this year, cities like Medellín have staged remarkable recoveries. And in the upscale districts of Bogotá, the capital, it is almost possible to forget that the country remains mired in a devilishly complex four-decade-old war.

But it is a different story in the mountains of the Nariño department. Here, and elsewhere in large parts of the countryside, the violence and fear remain unrelenting, underscoring the difficulty of ending a war fueled by a drug trade that is proving immune to American-financed efforts to stop it.

Soaring coca cultivation, forced disappearances, assassinations, the displacement of families and the planting of land mines stubbornly persist, the hallmarks of a backlands conflict that threatens to drag on for years, even without the once spectacular actions of guerrillas in Col****ias large cities.

For those caught in the cross-fire, talk of a possible endgame for the war seems decidedly premature, even given the deaths this year of several top guerrilla leaders, the desertion of hundreds of rebels each month and the rescue of prized hostages like the former presidential candidate Ingrid Betancourt.

The armed groups are like malaria, evolving to resist eradication and killing with efficiency, Antonio Navarro Wolff, governor of Nariño and a former guerrilla from the defunct M-19 group, said in an interview. If anything, Nariño shows the guerrillas may have lost their chance for victory but not their ability to cause suffering.

Today, a dizzying array of armed groups lord over the farmlands of Nariño. These include not only leftist guerrillas from the Revolutionary Armed Forces of Col****ia, or FARC, but also right-wing militias operating under names like the Black Eagles or the Peasant Self-Defense Forces of Nariño.

Their presence reflects the symbiotic nature of the armed groups and the drug trade, each drawing strength from the other.

In Nariño, flanked by the Pacific Ocean on the west and Ecuador on the south, coca growers have nimbly sidestepped almost a decade of fumigation efforts by reorganizing industrial-size farms into smaller plots that are much harder to find and spray from the air. They are taxed and protected by forces on the various sides of the conflict.

The United Nations reported in June that coca cultivation in Col****ia surged 27 percent in 2007 to 244,634 acres, the first significant increase in four years. Nariño had the largest increase of any Col****ian department, an administrative district, up 30 percent to 50,061 acres.

The expansion has allowed Col****ia to remain by far the worlds largest coca producer and the supplier of 90 percent of the cocaine consumed in the United States.

It has also made the drug-fueled conflict a resilient virus in large pockets of the country, with double-digit increases in coca cultivation in at least three other departments, Putumayo, Meta and Antioquia. In Nariño, almost every week, government officials, Roman Catholic leaders or aid workers report actions by the rebels or paramilitary groups.

In the last week of June, four schoolteachers in remote areas of the province were killed by a FARC column called Mariscal Sucre, one of three units of the FARC that are active in the area. The rebels claimed that the schoolteachers, all of them recently posted to remote schoolhouses by Roman Catholic officials, were army informants.

The guerrillas left the bodies of two of the teachers in front of their schoolhouses, preventing their families from giving them a Christian burial because the families were too afraid to collect the bodies, said Eduardo Muñoz, human rights director at Simana, the Nariño teachers union.

Just weeks before, in April, the FARC knocked out power for 300,000 residents along the Pacific coast with an attack on an electrical station. Col****ian soldiers also found eight fuel-processing depots holding 77,000 barrels of oil used by the guerrillas for fuel and to process coca into cocaine in makeshift labs.

Nationwide, the FARC still collects $200 million to $300 million a year by taxing coca farmers and coordinating cocaine smuggling networks, according to Bruce Bagley, a specialist on the Andean drug war who teaches at the University of Miami.

That is down from $500 million earlier this decade, Mr. Bagley said, but it is still enough to finance the FARC after recent desertions and killings that have thinned its ranks to about 9,000 from 17,000.

Similarly, while the FARCs share of the cocaine trade has declined, Col****ias share of the world cocaine production has remained stable at about 60 percent. That means opportunities for new players like Col****ias resurgent right-wing militias and small-scale armed gangs taking the place of disassembled cartels.

A few battles won is not a war won, Mr. Bagley said. The FARC and other groups will survive as long as there are safe havens, the flow of drug money and large, remote regions unconnected to the broader economy.

One such area is El Rosario, a municipality three hours from Pasto, the capital of Nariño, by four-wheel drive on winding switchbacks along the spine of the Andes.

A decade ago, coca was a rare crop in the area, farmers in El Rosario said. Then, eradication efforts under Plan Col****ia, the $5 billion counterinsurgency and antinarcotics effort financed by the United States, forced the migration of coca cultivation here from other parts of the country.

To them, the eradication effort has simply pushed the coca and the groups that feed off it into ever-more isolated parts of the country. Now that coca has become their livelihood, too, the farmers are determined to hold on to it.

At one remote spot, a 45-minute hike from a section of the dirt road, Liborio Rodríguez maintains a small coca field on a slope that has been subjected to aerial spraying and direct eradication efforts in recent years.

I know nothing is eternal, but I am not leaving this land, said Mr. Rodríguez, 41, while he and half a dozen laborers harvested leaves off coca bushes under the hot sun, pausing to sip chicha, an alcoholic drink made from corn. After everything we have been subjected to, I feel that I can survive here.

He and the other farmers say they have developed strategies to protect their coca bushes, planting smaller plots under canopies of trees and coating their leaves with sugar cane juice, thought to prevent phosphate-based herbicides from sticking.

In an example of unintended consequences, the phosphates repelled from coca bushes may soak into the ground and serve as a fertilizer, some botanists say, helping increase coca yields.

Other coca farmers have developed hybrid varieties of coca that grow lower to the ground and can be harvested four to six times a year, almost double previous levels.

Faced with the unexpected surge in coca cultivation in Nariño and other areas, Col****ian officials take comfort in findings by the United Nations that cocaine production in the country is believed to have remained stable in 2007, at about 660 tons.

And they say cultivation could have been much larger than the 543,630 acres measured last year were it not for the aerial spraying and manual eradication efforts, c****ined with strides in intercepting cocaine shipments and military victories against the FARC in numerous rural redoubts.

Yet while interdiction levels are promising, the growth of coca cultivation also promises the FARC and rival groups new opportunities to profit from the cocaine trade.

One paramilitary group, the Black Eagles, has so terrified residents of El Rosario that they will hardly utter the militias name when discussing how it extorts payments from them each month.

Elsewhere in Nariño, residents similarly report that paramilitary groups are thriving, despite government efforts to demobilize more than 30,000 paramilitary c****atants in recent years.

These militias, sometimes in camouflaged uniforms bearing the letters A.C.N., the initials in Spanish for Peasant Self-Defense Forces of Nariño, or O.N.G., for New Generation Organization have uprooted villagers near the Pacific coast, according to testimony collected by aid workers, as paramilitary groups, guerrillas and small-scale drug gangs struggled for control of cocaine smuggling routes.

Government figures suggest that displacements are declining in Nariño, with about 7,500 people forced from their homes so far this year in comparison with almost 30,000 in all of 2007. But other agencies paint a more distressing picture.

Codhes, a leading human rights group, said overall displacements in Col****ia climbed 38 percent last year to more than 300,000, with Nariño emerging as the center of Col****ias humanitarian crisis, said Jorge Rojas, the groups director.

Seemingly marginal organizations persist in pockets of rural distress. Another leftist rebel group, the National Liberation Army, or E.L.N., has at least 100 c****atants in the area, local officials and aid workers said.

A FARC rival that has been vastly diminished in recent years, the E.L.N. normally avoids involvement in the cocaine trade. But its riches are so tempting, community leaders say, that a rogue column of the group in Nariño, Comuneros del Sur, has secured a new lease on life by financing itself through drug deals.

In June, three boys from the Awá indigenous group walked into a rural area planted with land mines by the E.L.N., community leaders said. The boys, ages 8, 12 and 15, were instantly killed, placing them among 31 victims of land mines in Nariño this year, a grim figure that includes 19 civilians, according to Col****ias government.

Our view is that all sides are not weakening but getting stronger, said an Awá leader, asking not to be identified out of fear of retribution from the rebels. Where else in the world can the authorities claim to be winning when their opponents continue planting both coca and mines?