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Wildlife, Marijuana And Rat Poison: Tackling A Toxic Legacy In California

After nearly 20 years in a legal gray zone, medical marijuana in California is being brought under regulation. But clandestine pot cultivation continues. Illegal grows on public land are especially notorious for causing a range of environmental problems. Now, there's new research that zeroes in on the toll these trespass grows take on threatened wildlife.

Several years ago, federal wildlife managers wanted to find out whether Pacific fishers qualified for protection under the Endangered Species Act. For years, the weasel-like cousin to the wolverine has been declining throughout California, Oregon and Washington.

While studying how fishers are dying, researchers found something unusual in the tissues of dead fishers: anti-coagulant rodenticides … rat poison. Dr. Robert Poppenga describes how these poisons work.

“They prevent the blood from clotting by interfering with Vitamin K, so if you don’t have it, there’s nothing to stop the hemorrhage, so these animals basically bleed to death,” he says.

Poppenga is a veterinary toxicologist with the University of California Davis. Since 2007, Poppenga’s lab has examined the bodies of 167 fishers. He says about 10 percent of them died by poisoning, and many more were contaminated at less-than-lethal levels.

“In about 85 percent of these animals we find at least one anticoagulant rodenticide present in their bodies,” he says. “In many of these animals we actually find more than one.”

Dr. Mourad Gabriel -- with the non-profit Integral Ecology Research Center in Humboldt County, California – says the team began looking for the source of the poisons. They eliminated government agencies, power companies, timber companies, private landowners.

Then, Gabriel says, law enforcement officers invited the researchers to come along on raids of trespass marijuana grows on public lands.

Bingo …

“Our team has collectively visited close to 200 sites in California,” Gabriel says. “And about 95 percent of those sites have some type of rodenticide present.”

Gabriel says these illegal grow operations are typically way in the back country, and the workers who live there often leave a huge toxic mess on the landscape.

“The human waste, the garbage, the food, the rodenticides … and then you now take that picture of one site and then you extrapolate that to thousands of sites in California.”

When law enforcement officers raid these back country grows, they destroy the marijuana crop, but there’s often no money to clean up the trash and poisons left behind. Gabriel says these sites could easily contaminate soil, waterways, even entire food webs.

“If we don’t do something about this sooner than later, we’re going to leave a legacy effect,” he says.  “And it’s going to occur not just for the wildlife or the fisheries, but the indirect and direct impacts are going to affect everybody,” he says.

Jim Wood agrees. Wood is a Democratic member of the California Assembly whose district encompasses much of the state’s prime pot growing territory.  He’s sponsoring a bill that would create a fund to pay for enforcement of water and land use regulations and cleanup of toxic trespass grows.

“We’re asking for the legitimate cannabis cultivators to pay a fee based on their crop to help us to go after the people who are creating a problem for them and a problem for our environment,” he says.

Wood estimates his bill would generate about $20 million a year for cleanup. And the legitimate cannabis cultivators seem to be on board with that.

Hezekiah Allen, head of the California Growers Association, says they’re very much in favor of cracking down on irresponsible marijuana operations.

“We absolutely agree that there needs to be an investment in cleanup and remediation first,” he says. “But we would also like to see a long-term investment into conservation and restoration.”

Allen notes the region’s environment was damaged by reckless mining, ranching and timber extraction long before abusive pot growers began contributing to the problems, and that many of those impacts persist.

“And we don’t just want to clean up the messes that this industry has made. We want to be part of a long term solution to restore those watersheds, to restore those fisheries,” he says.

That would go well beyond the scope of Assembly member Wood’s pending bill.

That bill is expected to be considered after the Assembly reconvenes in January.

Liam Moriarty has been covering news in the Pacific Northwest for three decades. He served two stints as JPR News Director and retired full-time from JPR at the end of 2021. Liam now edits and curates the news on JPR's website and digital platforms.