Aug. 12, 2008 -- When most people think of national forests, visions of trees and wildlife come to mind. But national forests have become a hotbed of narcotics trafficking.
Large expanses of the Northern California wilderness, typically used for camping and fishing, have been replaced by manicured rows, consisting of tens of thousands of marijuana plants.
Marijuana is being grown illegally on national park land in seven states: California, Tennessee, Washington, Oregon, Kentucky, Hawaii and West Virginia, according to the Office of Drug Control Policy.
An epidemic of illegal marijuana farming on public lands has spread, fueled by Mexican-based drug dealers who have sent a covert work force into the mountains.
The dealers hide the marijuana deep in the forest, on land often accessible only on foot. ABC News traveled with DEA agents, by helicopter and then through steep terrain to reach the fields.
Across thousands of acres of national forest, dealers have painstakingly laid miles of elaborate waterlines through the forests to irrigate their crop. Each marijuana plant has been carefully positioned to receive its own water supply and maximum sunlight.
This extensive cultivation operation produces massive marijuana plants, some 15 feet tall, sprouting buds the size of ears of corn.
While marijuana crops flourish, millions of forest plants and trees are destroyed.
"Ten acres of forest are damaged for every acre planted with marijuana," said John P. Walters, the director of National Drug Control Policy, in a recent testimony. (Walters is known as the "drug czar.") The land, he continued, is "contaminated with the toxic chemicals, fertilizers, irrigation tubing and pipes associated with marijuana cultivation."
The dealers redirect water from the forests' streams, building dams that dry out parts of the forest.
"Water's not flowing where it naturally should; instead it's right here in a pool," said Jeffery Hoyt, group supervisor for Marijuana Group, and a San Francisco DEA agent.
As they devvastate the environment, the dealers reap massive profits -- 1 pound of marijuana is valued at $3,000 on the streets.
Hoyt brought ABC News to the middle of the forest, where workers built a drug trafficker's camp, complete with the comforts of home.
"They've got it netted, they've brought their own power source," Hoyt explained. "Packages of beer, Coca-Cola, peaches, and then they pack all their clothing in it. Everything you need to survive in the woods."
There was even a log of work hours, with what appeared to track names, dates and times.
"A lot of these people are paid 200 bucks a week," Hoyt said, thumbing through the drug dealer's notebook.
Police surveillance photos show that the dealers are often armed. The DEA has seized almost 191 weapons from the San Francisco fields.
"We're finding more and more that the growers are arming themselves," Hoyt said. "It's becoming a more dangerous situation for law enforcement."
After searching the area for traffickers, the DEA agents destroyed the crops on several acres of mountainside. In this area of California alone, the DEA found 2,349 marijuana plants, worth an estimated street value of $9 million.
So far this season, the DEA has cut down more than 168,000 marijuana plants in California. And the growing season's not over yet.