​Due to the enormous profits made possible by marijuana prohibition, Mexican drug gangs are taking over U.S. public land to grow cannabis, using smuggled immigrants to cultivate the plants.

Pot has been grown on public lands for decades, report Alicia A. Caldwell and Manuel Valdes of the Associated Press , but Mexican cartels have taken clandestine cannabis cultivation to a whole new level, using armed guards and trip wires to secure grow operations containing tens of thousands of plants.

“Just like the Mexicans took over the methamphetamine trade, they’ve gone to mega, monster gardens,” said Brent Wood, supervisor for the California Department of Justice’s Bureau of Narcotics Enforcement. Wood claimed the Mexican traffickers have “supersized” the marijuana trade.

Each year between 2004 and 2008, local, state and federal law enforcement agents found a million more pot plants than the year before. Authorities claim an estimated 75 to 90 percent of the new marijuana farms can be linked to Mexican drug gangs.

In 2008 alone, according to the federal Drug Enforcement Administration (DEA), officers across the country seized or destroyed 7.6 million marijuana plants from about 20,000 outdoor plots.

Growing cannabis in the United States saves traffickers the risk and expense of smuggling the pot across the border and allows the cartels to produce their crops closer to local markets.

Distribution also becomes less risky, AP reports. Once the pot is harvest and dried on the clandestine farms, cartels can drive it to major cities, where it is distributed among street dealers and sold along with Mexican-grown weed.

One of the only risks to the Mexican growers, according to experts, is the possibility of a stray hiker or hunter stumbling across a hidden field.

All of the sites are in remote plots, far from the eyes of law enforcement.

Mexican cartel plots can often be distinguished from those of domestic-based pot growers, who usually cultivate much smaller fields with no security measures.

Some of the fields tied to drug gangs have as many as 75,000 plants.

AP says that Sequoia National Forest in central California is “covered in a patchwork of pot fields” hidden along mountain creeks and streams, away from hiking trails. It’s much the same situation in nearby parks like Yosemite and Redwood national parks.

News reports claim that many of the plots are “encircled with crude explosives” and “are patrolled by guards armed with AK-47s.”

Moyses Mesa Barajas had just arrived in eastern Washington state from the Mexican state of Michoacan when he was approached to work in a pot field. He said he was taken almost immediately to a huge crop hidden in the Wenatchee National forest, where he managed the watering of the plants.

Barajas was arrested in 2008 on a raid and sentenced to more than six years in federal prison. Several other men fled before police could grab them.

“I thought it would be easy,” he told the AP in a prison interview. “I didn’t think it would be a big crime.”

Vast amounts of marijuana are still smuggled into the United States from Mexico. Federal officials report busts of hundreds or thousands of pounds almost every day at the border. But drug agents say the boom in domestic growing is a sign of diversification.