Top Mexican cartels like Sinaloa and Jalisco Nueva Generacion - which have large areas of influence within Mexico and engage in brutal violence for control of drug routes - have long purchased cocaine from Colombia's guerrilla groups and crime gangs.
But while they once operated as discrete buyers - and still avoid direct engagement in the competition for their business - the increasing presence of emissaries is noticeable in several cocaine-producing areas, residents and farmers told Reuters.
The cartels have driven significant changes in the varieties of coca being planted, sending cocaine production higher, Colombia's anti-narcotic police say. These developments in how coca is grown have contributed to the increased quantity and purity of cocaine trafficked to both the United States and Europe, the police say.
The increased output from new coca strains is visible in figures from the United Nations Office on Drugs and Crime, with potential cocaine output rising over the last three years even as the planted area decreases.
Individuals are sent by cartels to guide production, as well as buying and transport, General Fernando Murillo, head of the DIJIN investigative division of Colombia's national police told Reuters.
"They do it for assurance and confidence in the purity of the substance that is being sold to them," he said.
Coca growers, informants and captured traffickers have detailed to police and the military how the Mexican emissaries conduct purity controls, maintain relations with the entire spectrum of Colombian armed groups and negotiate prices, Murillo said.
The extra fruitful coca seeds are the product of cartel-funded cultivation work by experienced farmers and agronomists, said General Ricardo Alarcon, director of the anti-narcotics police.
Over the last three years, his unit has detected 14 adaptations made to increase productivity. There is no evidence the seeds are genetically-modified, he said.
The U.N., police and military sources, as well as growers and human rights activists, agree that a recent surge in productivity was due to careful selection of high yielding varieties.
One coca grower in Norte de Santander province told Reuters cartel representatives and their Colombian business partners began distributing more fruitful varieties two years ago, ordering farmers to plant them.
Though the area planted with coca fell in 2020, 2019 and 2018, estimated cocaine production and average yield of cocaine hydrochloride per cultivated hectare rose each of those years, according to the U.N. figures.
In 2020, the most recent year for which figures are available, potential annual production was up 8% to 1,228 metric tonnes, while yield per hectare was up 18% to 7.9 kilograms.
Potential production refers to the quantity that would be produced if all coca leaves were processed into pure cocaine.
The cartels add another element to a complex landscape of violence in Colombia. The Mexican gangs are bringing high-powered weapons to the country from the United States to use as payments for shipments of cocaine.
Cartels purchase both coca base and high-grade cocaine from Colombian crime syndicates like the Clan del Golfo, the National Liberation Army (ELN) rebels and former members of the Revolutionary Armed Forces of Colombia (FARC) guerilla group who reject a 2016 peace deal, security sources in the police and army said.
"It's a very pragmatic relationship," Rafael Guarin, who was then serving as national security advisor to Colombia's president Ivan Duque, said in late 2020. "Whoever has control of the growing areas and the laboratories and can meet demand is the one who maintains relations with the Mexicans."
The presence of emissaries in coca-growing regions is visible, four people living in Cauca, Narino and Norte de Santander and one who recently visited Cauca told Reuters.
In one incident, two men with Mexican accents at a Cauca bar who discussed moving cocaine by truck got angry when a local man came too close, according to a waitress who overheard the conversation in 2020.
"We'll fill your stomach with lead," one said, revealing the pistol wedged into his waistband.
Reuters was able to corroborate some of the details described by the woman, who asked to remain anonymous, through security footage taken in the bar.
The cartels fund construction of laboratories and warehouses where shipments are coordinated, a police intelligence report seen by Reuters shows, and police sources say they also bankroll improvised docks and semi-submergible boats on the Pacific. Nearly all shipments are marked with logos used to control origin and quality, the report said.
Farmers said they had little choice but to plant the new strains.
"If someone arrives here with a gun, dressed in camouflage, or dressed like a civilian but with a gun in their belt and tells me that these are the seeds to plant, I just do what they say," said Fernando, a Norte de Santander farmer. "It's my life and that of my family."
"We don't ask who's buying, nor where they come from," he said, though he said he believed visitors to his area were Mexican cartel representatives because of their accents.
Cocaine can be obtained from four strains of the plant Erythroxylum, of which three - the novogranatense, coca and ipadu - are present in Colombia.
The most productive type varies according to climate - with some varieties thriving in colder areas and others heartier when it comes to resisting drought.
"It's an adaptation of the plant in different areas," said Alarcon, the anti-narcotics police director. "What the producers - of both coca leaves and cocaine hydrochloride - do is take advantage of the mutations."
The national police have recorded the presence of varieties colloquially or commercially known as 'tingomaria,' 'giant,' 'Bolivian black' and 'Bolivian red' in both Norte de Santander and Narino, the two top producers of cocaine.
Farmers are encouraged to rotate seeds to further increase output and reduce harvest times, Alarcon said. Some adaptations produce between four and six harvests a year, instead of a traditional three.
It is unclear if cartels prefer a specific modification.
More than half the cocaine leaves Colombia along its Pacific coast, security forces said. A key cartel alliance in the region is with the FARC dissidents, said Colonel Jaime Zambrano, head of the 4th Marine Infantry Brigade, as he rode a boat through the yellow waters of a jungle estuary near Tumaco, Narino.
The bumper crops and high demand mean business is good. The price for a kilo of high-quality cocaine rises more then eighteen-fold to $30,000 at the U.S.-Mexico border and to more than $120,000 per kilo within the United States, according to Colombian police.
In Colombia, the scarce state presence, poverty and lack of economic opportunities mean the cartels' offers of pay-outs for harvests, including in advance, are attractive to farmers, activists say.
"Drug trafficking has gone up because of the total abandonment of the state. There is no dignified housing, no dignified healthcare, we don't have dignified education or employment," said Tumaco social leader Luis Alfredo Vasquez.The situation is similar in Norte de Santander, where rising cocaine production has caused upticks in violence but where growers feel economic benefits.
"For the first time in many years coca growers in the region have cash upfront," said Wilfredo Canizares, head of the Fundacion Progresar human rights group.
(Reporting by Luis Jaime Acosta; Writing by Julia Symmes Cobb; Editing by Daniel Flynn, Julia Symmes Cobb and Frank Jack Daniel)
By Luis Jaime Acosta