America’s public lands are under siege from all sides, overrun by everything from hungry cows to oil rigs, facing $18 billion in maintenance backlogs and an administration seemingly hellbent on privatizing our parks and cutting old-growth forests.

Now, as if all that is not enough, international drug cartels are poisoning water and wildlife with lethal chemicals. The toxicants, including a banned neurotoxin and other poisons, are used on thousands of illegal marijuana farms hidden on federal, state, and tribal lands.

These so-called trespass grows are the work of highly organized drug cartels that take advantage of rugged terrain and thick vegetation to hide their operations. Some sites go undetected for years, according to NPR’s Morning Edition. An unlikely coalition of environmentalists, law enforcement, wildlife ecologists and people involved in the legal cannabis industry is working together to shut down illegal grows and mitigate the environmental damage they do, the program reports.


Agents clean up at a trespass grow. The trash can be hoisted out with a helicopter, but lethal chemicals persist in the land, water and food chain.

Morning Edition reporter Eric Westervelt recently accompanied conservationists and armed Forest Service agents to a grow site deep in Northern California’s Shasta-Trinity National Forest. Westervelt narrates as the group scrambles down a steep hillside and through a tangle of Douglas fir, madrone and “big leaf maples turned golden yellow.” Finally, he says, the forest gives way to a sprawling growing site and campsite, its “terraced plots carved erratically into a hillside scarred by wildfire.”

Authorities had raided the site in September, arresting two Mexican nationals suspected of being linked to the cartels that control upwards of 90 percent of the trespass grows in the United States.

These guys weren’t exactly practicing leave-no-trace. The site was strewn with some 3,000 pounds of trash, everything from old clothes and propane tanks to three miles of plastic irrigation pipes.

The most disturbing find, however, was the discarded containers of rat poison and commercial insecticide strewn about. Wildlife ecologist Greta Wengert showed Westervelt an empty carton that had once held bait blocks of Bromethalin, a neurotoxin rodenticide.

Nearby, she pointed out the spot where she’d found a container of concentrated carbofuran, a poison so powerful that “a quarter-teaspoon could kill a 600-pound black bear.” The empty jug once held a gallon of the stuff.

Dr. Mourad Gabriel at a cleanup of a trespass grow on public land in California. Flickr

The U.S. Environmental Protection Agency enforces a complete ban on domestic use of carbofuran, though Pennsylvania-based FMC Corp manufactures it in the U.S. for export to a handful of countries that still permit its use, including Mexico. It’s marketed as an insecticide, but the cartels use the persistent compound to kill rodents and other wildlife that threaten their multi-million dollar groves. Now it’s everywhere gravity and the food chain can take it.

“We have detected [carbofuran] in the soil, in cannabis plants, in native vegetation, the water, the infrastructure,” said Wengert, who in 2004 co-founded the Integral Ecology Research Center with her husband, Mourad Gabriel. The couple started the California nonprofit to protect sensitive wildlife species and their habitats. That mission brought them face-to-face with the rapidly expanding problem of chemical contamination from illegal marijuana operations.

Gabriel and Wengert have studied samples taken from more than 300 grow sites and found a stark increase in the presence of toxic chemicals at the sites and in the bodies of animals found nearby, the Sacramento Bee reported last year. Gabriel said that the presence of such chemicals at grow sites has increased from 12 percent in 2012 to 78 percent five years later.

The number of illegal pot farms continues to grow, even as marijuana use has been decriminalized in much of the country and is now legal, in one form or another, in California and 11 other states. A veteran Forest Service agent told National Geographic that 2000 was the first year that California’s Trinity County removed more than 1,000 cannabis plants. By the end of that decade, the count was in the hundreds of thousands. In 2018—the same year California legalized recreational marijuana—the agency removed more than a million plants.

It’s a big problem. Gabriel and Wengert studied the Pacific fisher, an endangered carnivore native to northern California’s pot-growing Emerald Triangle, finding that 46 of 58 fisher carcasses they tested had been exposed to rodenticide believed to come from illegal marijuana farms.

Fishers, an endangered weasel-like predator, are the canary in the cannabis fields. Photo courtesy Phil Johnston, Lost Coast Interpretive Association.

“Before long, they realized other species were being exposed, including bears, grey foxes, bobcats, mountain lions, and the northern spotted owl, another threatened species in California,” Morning Edition’s Westervelt writes. “Some were exposed by accident. Others seemed to have been baited and intentionally poisoned. They’ve found pesticide-laced hot dogs on hooks in the forest. Another time, they discovered a vulture that had died while feeding on a poisoned grey fox. The carcasses were surrounded by dead flies.”

Think about that for a minute. The poison is so lethal it passed from the fox to the vulture, and then killed the flies that fed on them.

At another grow last spring, Gabriel showed a National Geographic film crew a perforated plastic bottle. “You see there’s a bear puncture in this,” he says. “If it’s carbofuran, that bear’s done. This has federally been designated critical habitat, and we have what I call a death ring, a death pit. If that bear is raising young, [this] didn’t just kill that sow. [It] killed her and maybe her two or three cubs that she’s raising.”

Trespass grows are hard on fish as well, both because of the poisons leached into streams and the large quantities of water used for irrigation. Growers often pull water from small tributaries in August and September, when streams are naturally low and salmon are on the move. Scott Bauer, a senior environmental scientist with the California Department of Fish and Wildlife, says young fish can be trapped in disconnected pools. “It’s a serious issue for the coho salmon,” Bauer told The Nation in 2013. “How is this species going to recover if there’s no water?”

With thousands of illegal grows across the country, the environmental damage is significant, and it’s real. This is not just a case of Reefer Madness hysteria (though it makes one wonder whether it’s safe to smoke). Gabriel isn’t fighting marijuana, he’s fighting the spread of toxic chemicals through the ecosystem. “I do this work because it’s a conservation issue,” he said.

Pin It on Pinterest