Visits to Chequamegon-Nicolet National Forest in Wisconsin come with a warning these days.
It's not ticks that forest officials tell hunters, anglers and hikers to worry about. It's not lightning or dangerous weather. It's not even black bears, timber rattlesnakes or the mountain lions that roam wild in the state for the first time since 1910.
Industrial-scale marijuana "grows" -- hidden plantations that are cultivated by organized drug cartels, guarded by armed groups of illegal immigrants and worth millions of dollars -- once were confined to the western United States, but they have moved eastward and popped up on the Chequamegon-Nicolet.
"Drug trafficking-organization marijuana growers are dangerous and are known to carry firearms," reads an alert on the forest's website. "The (forest) asks that visitors be aware of their surroundings and know what to do to remain safe."
From 2008 to 2012, law enforcement officials eradicated 67,827 marijuana plants from the Chequamegon-Nicolet, according to forest spokeswoman Megan Healy. They're aware of 75,000 plants that growers harvested before officials got to them.
There's an environmental cost to the operations, Healy noted. The grows spawn erosion that clouds native trout streams. They diminish wildlife as guards destroy habitats and poach animals for food and to keep them from nibbling the crop. They foul drinking water with pesticides and human waste from primitive camps.
Cleaning that up can cost as much as $15,000 an acre, according to U.S. Forest Service statistics.
Drug operations present high-stakes threats to people, too, said David Spakowicz, eastern region director of field operations for the Wisconsin Department of Justice.
A single marijuana plant might be worth a minimum of $1,000, he said. A grow with 10,000 plants -- not unheard of -- could therefore be worth $10 million.
"People might look at this and say, 'Oh, it's just weed.' Well, no. These grows pose a huge danger to the recreational public with all of the money to be made," Spakowicz said.
"If you haven't seen this in Pennsylvania, you're very, very lucky."
A common problem
Large-scale cultivation of drugs on public land is a phenomenon that began in California in 1995. As of last year, the practice had spread to 68 national forests in 20 states. Pennsylvania is not among them.
But that doesn't mean drugs aren't a part of Pennsylvania's wildlands. People have grown marijuana on public land here since the late 1960s -- just not on the scale of what occurs in places such as Wisconsin, said Rich Palmer, chief law enforcement officer for the Pennsylvania Game Commission.
"We find cultivation sites on game lands throughout the state. Pretty much every region experiences it, to some degree, pretty much every year," he said.
Officers in Western Pennsylvania have investigated cases involving individual plants and spots with as many as 250, from Washington to Westmoreland counties, said Scott Tomlinson, law enforcement supervisor in the commission's Southwest Region office in Bolivar.
Dan Sitler, a conservation officer in Washington County, said that in 2011, he confiscated 21 7-foot-tall marijuana plants from State Game Lands 117 near Burgettstown. He got 36 plants last year.
"I've always said I don't think there's a game land in the state that doesn't have some kind of marijuana on it. It might be one plant or dozens, but it's there," Sitler said.
Marijuana is common in Pennsylvania's national forest, the Allegheny, said Steve Burd, a ranger there for 16 years who oversees law enforcement in national forests in Pennsylvania, New York, Vermont, New Hampshire and Maine.
A typical Allegheny "garden" might include 25 plants, though some have contained as many as 100, he said.
"Marijuana growing on a national forest has been around throughout my career, and it was around before that, too," Burd said.
But for state parks, it's a "non-event," said Department of Conservation and Natural Resources spokesman Terry Brady. They're typically too small and too populated to offer the secrecy growers desire, he said.
Less developed, more remote state forests attract growers.
"The scale of it varies from year to year," said Jason Hall, recreation section chief for the Pennsylvania Bureau of Forestry. "A lot of times, the marijuana isn't even planted in the ground. It's in pots people carried into the woods."
Ed Callahan, district forester for Forbes State Forest, based in Laughlintown, said officials find larger marijuana operations on occasion, such as a few years ago in Fayette County.
"We had some fairly large grows actually," Callahan said. "I think these people are looking for the most remote place where they can to do their thing out of sight."
Hobby or business?
The smaller size of the marijuana operations found on Pennsylvania's public lands doesn't mean they're only for private use.
Criminals are just trying to be smarter these days, authorities say.
"The more common thing now is for people to plant smaller plots -- but more of them. It's playing the odds," Palmer said. "That way, even if you lose half your plots, you still have something."
Having fewer than 20 plants in one location keeps the crime at a misdemeanor level if a grower is caught, Sitler said.
Still, growers don't like to lose or give up plants.
Armed guards patrol large-scale grows in other states, and booby traps aren't uncommon.
Both are rare in Pennsylvania, but growers have encircled plots with monofilament line laced with fish hooks and hung it at eye level, or placed trip wires connected to firing devices that could set off shotgun shells, Palmer said.
"If you see something that looks suspicious, you don't want to just go in there stomping around," Tomlinson said. "It's a real public safety issue, in our eyes.
"That's why the message we want to send to people who might want to do this is, 'We're not just interested in finding this stuff; we're interested in finding you and prosecuting you for it.' ... We want to solve the problem, not just move it."
Authorities confiscated 3.34 million marijuana plants from national forest land in California in fiscal year 2009, according to the Forest Service. By fiscal 2012, the total fell to about 838,000 plants.
Some worry that enforcement efforts move, rather than eliminate, grows.
But economics might be behind growers' expansion to the Midwest, though, Spakowicz theorized. Growing plants closer to cities where people buy the drug cuts the risk of getting caught and reduces transportation costs, he said.
Is it reasonable to suspect, then, that drug growers might move into Pennsylvania's forests to avoid legal pressure and get closer to markets in Pittsburgh, Philadelphia and New York?
Adam Reed, a Pennsylvania State Police public information officer, said there's no indication that that's occurring.
"And hopefully the trend doesn't make its way this direction," he said.
Burd thinks the nature of public lands in the East might make it hard for big grows to work. About 2.1 million acres comprise Shasta-Trinity National Forest in California, which accounted for nearly 610,000 marijuana plants confiscated in 2010 -- about 60 percent of the national total. Wisconsin's Chequamegon-Nicolet spans about 1.4 million acres.
Allegheny National Forest, by comparison, has less than 600,000 and is crisscrossed with roads.
"You get a lot of fishermen up there, a lot of hunters, a lot of hikers," Burd said. "There aren't millions of acres of undisturbed forest ... for people to hide."
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