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Many of this country's public lands are facing a toxic threat. Drug cartels are growing marijuana inside many national forests and parks. Now, this is an old problem, but there's new research showing that the pot is poisoning the wildlife food chain and doing long-term environmental damage. NPR's Eric Westervelt reports from Northern California's Shasta-Trinity National Forest.
ERIC WESTERVELT, BYLINE: Deep into the Shasta-Trinity on a warm fall day, a group of armed Forest Service Police carefully make their way down an isolated hillside above a creek.
UNIDENTIFIED FOREST SERVICE POLICE OFFICER: Yeah, let's go this way.
WESTERVELT: Holy cow - this is steep.
UNIDENTIFIED FOREST SERVICE POLICE OFFICER: You know, they oftentimes choose very remote locations where people aren't going to stumble into.
WESTERVELT: We make our way through Douglas fir and madrone trees and big-leaf maples turned golden yellow. At spots, it's so steep a rope is needed. Elsewhere, we kind of surf-slide tree to tree down the mountain.
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UNIDENTIFIED FOREST SERVICE POLICE OFFICER: Give it a 7.5.
WESTERVELT: The steep forest finally gives way to a sprawling marijuana grow and campsite. It's typical in shape - terraced plots carved into a hillside scarred by wildfire. The burned trees and new growth offer some cover from air surveillance.
The police arrested two Mexican nationals here last month and pulled up all the plants. They're coming back this day with scientists and environmentalists to assess the cleanup.
The three camps, spread out over half a mile, clearly accommodated more than the two arrested. Plastic tarps cover several trash-strewn sleeping and food areas filled with detritus of a weed-growing life deep in the woods.
There's a sleeping bag, an arrow. There's an old mattress, a brush, homemade slingshot and lots of garbage.
The Forest Service estimates there's at least 3,000 pounds of trash here, an indication this site may have been used for years. Most will have to be hauled out by helicopter.
But that's hardly the biggest problem. Plastic irrigation lines snake around a makeshift kitchen littered with spent bottles of insecticide, open bags of fertilizer. Nearby, scientists found bags of bait blocks to kill rodents.
GRETA WENGERT: This one is bromethalin, which is a neurotoxicant rodenticide.
WESTERVELT: Dr. Greta Wengert is a wildlife ecologist who studies the impact of these illegal grows on forest ecosystems. She was here when the arrests were made. She points to a tree where they found about a gallon of concentrated carbofuran. That's an insecticide banned in the U.S. for all legal purposes.
WENGERT: It is incredibly toxic. A quarter teaspoon could kill a 600-pound black bear. So obviously, just a tiny amount can kill a human. It remains in an ecosystem for a long period of time.
WESTERVELT: Trespass pot-growing is a decades-old problem, from hippies to cartels. But what's new is that cartel growers are using more poisons, Dr. Wengert says, and spreading them indiscriminately - on the pot, the soil, all around.
They do that to protect their cash crop from insects as well as rodents, who like to chew into the plants for water. And an increasing body of research, including her own, shows alarming levels of pesticide and insecticide contamination of the entire wildlife food web in the state's national forests.
WENGERT: The mountain lion population in California is exposed at a rate well over 90%. We're just getting data on rodents, the prey base for all the species that are of concern when you're talking - mountain lions, fishers, spotted owls, other forest raptors. The prey base that is supporting those species is contaminated.
WESTERVELT: That means they're also starting to see damage to wildlife offspring, including Pacific fishers, an elusive carnivore in the weasel family. It's a candidate for listing under the Endangered Species Act.
Dr. Mourad Gabriel, a wildlife disease ecologist, has documented that 85% of California fishers have been exposed to rodenticide.
MOURAD GABRIEL: In fishers, for example, there is in utero transfer and mother milk transfer as well. The female is transferring that anticoagulant rodenticide to her fetuses, or when she has birth and she gets exposed, she can transfer through that mother's milk.
WESTERVELT: And when fishers and other exposed wildlife die, a whole host of animals and insects feed on the carcass, spreading the poisons further.
GABRIEL: It is very similar to the same long-term legacy effects that DDT posed back in the day.
WESTERVELT: That infamous insecticide nearly wiped out several species, including the bald eagle, before it was banned here in 1972.
This site is uphill from a major creek. There's evidence waterways and fish are being harmed as well.
The Forest Service doesn't really know how many sites are out there in public forests. They estimate they bust fewer than half. Kevin Mayer, a Forest Service supervisory special agent, says the arrests they do make are almost all drug cartel-related.
KEVIN MAYER: Ninety-eight percent of those are all Mexican nationals, usually in the country here illegally from Michoacan, Mexico.
WESTERVELT: Michoacan is home to one of the powerful cartels. Despite legalization in 11 states, there's a thriving black market for pot, and drug cartels see a way to make fast cash. This site alone produced nearly 9,000 plants, Mayer says, worth some 1.5 million on the black market.
MAYER: It's worth the risk for them, they think, to come out here and basically destroy our public lands. You know, that's the - the true crime here is the fact that they're killing off, basically, America's public lands. Killing off the wildlife, killing off our water - this is stuff that - you know, it's not going to repair itself.
WESTERVELT: And the Forest Service simply doesn't have the boots on the ground to help repair the damage, let alone stop the grows. Mayer has just six law enforcement agents to patrol the entire 2.2 million-acre Shasta-Trinity, California's largest national forest.
The agency also doesn't have any reclamation or hazmat teams to deal with this expanding problem. Rich McIntyre directs CROP, the Cannabis Removal on Public Lands Project. It's a new group trying to get more public funding to clean up these sites and boost police and science support for the issue.
RICH MCINTYRE: The public is blissfully unaware of the problem because it's very much out of sight, out of mind. The Forest Service is grossly underfunded on a number of fronts, not just on a law enforcement front but on the scientific front as well. And that's something that we hope to change.
WESTERVELT: In California alone, there's currently a daunting backlog of some 2,000 contaminated illegal grow areas - 2,000 mini toxic sites in your national forests waiting for a basic cleanup.
Eric Westervelt, NPR News, Shasta-Trinity National Forest.
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