Mexico City (AFP) - The growing legalization of cannabis in the United States is forcing Mexico's drug cartels to rethink their illicit business model, turning to opium poppy plantations and domestic pot consumption, experts say.
Americans have been legally allowed to light up joints in the US capital since late last month, joining Washington state and Alaska, while Oregon will follow suit in July.
A total of 23 US states have legalized the drug for medical use, and opinion polls show that a slim majority of Americans favor legalization.
The changes in the world's biggest drug market appear to have prompted the criminal organizations producing narcotics in Mexico to switch strategies.
"As (US) domestic production increases, this will affect production in Mexico," Javier Oliva, a security expert at the National Autonomous University of Mexico, told AFP.
Drug cartels "will seek to increase their exports to Europe and the opportunities for consumption within the country," he said this week at a presentation of a report by the International Narcotics Control Board, a United Nations agency.
- Growing poppy fields -
With Americans now able to grow their own cannabis in many places, one market the cartels appear to be tapping is the growing consumption of heroin in the United States.
Oliva said the number of opium poppy fields has surged by 300 percent in the last five years in Mexico's southwestern state of Guerrero, one of the country's most violent regions, where 43 students were allegedly slaughtered by a police-backed gang in September.
The scarlet blossoms are also popping up in the north, including in the state of Durango, which forms a "Golden Triangle" of drug plantations with the neighboring regions of Chihuahua and Sinaloa.
Poppy fields outnumber marijuana plantations by three to one, said Adolfo Dominguez, a military commander in Durango.
"The criminals have obviously seen an improvement in this type of cultivation and they also pay attention to the demand factor," Dominguez told AFP.
Heroin consumption in the United States has surged due to tighter controls of prescription opioid drugs, said Alejandro Mohar, a member of the International Narcotics Control Board.
"Opiate-dependent drug users are increasingly turning to heroin, which is typically easier to source and cheaper than prescription opioids," the board's report says.
"Law enforcement authorities in the region have also identified significant increases in heroin purity," it says.
The US heroin market was worth an estimated $27 billion in 2010. But marijuana is a more lucrative business, worth $41 billion that same year, according to US government figures.
- Local smokers -
America has a huge appetite for marijuana.
More than 1,000 tonnes of marijuana are seized along the US-Mexico border every year, the report says, citing US Drug Enforcement Administration figures.
And the cannabis confiscated by US customs authorities represented 94 percent of worldwide seizures in 2013.
With Americans now able to grow their own, higher-quality marijuana in some places, Mexican drug cartels will look to sell their weed to local consumers, experts say.
Cannabis now ranks third after alcohol and tobacco in a government ranking of "drugs of impact" that require some kind of medical treatment, said Raul Martin del Campo, representative of the National Commission Against Addictions.
Movements to legalize marijuana have also emerged in Mexico, including in the capital, with the backing of a former president, Vicente Fox.