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Home > Articles > Cultivation > Content Piece

The Environmental Cost of Illegal Cannabis Cultivation

By Leo Bear-McGuinness

Published: Jan 04, 2022   
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Deep in the national forests of California, hidden under a canopy of trees, lie the engines of a criminal enterprise. Nestled between bark and bush, thousands of cannabis plants grow alongside their taller birch, pine, and cedar cousins. These aren’t legal crops. They aren’t regularly inspected by a state official or destined for state-approved processing and testing. They’re grown clandestinely in the woods for the illicit market, which remains strong in California despite the legal market nearing its three-year anniversary.

While the image of an illegal cultivator tending to their cannabis among nature might seem peaceful, even idyllic, the reality is far more unsettling. These covert cannabis farmers often use toxic and illegal pesticides to protect their crops from curious wildlife. And these pesticides are killing wild animals in their droves.

“It’s estimated that there are several thousands of these sites on public lands in California,” says Dr Greta Wengert. “Nearly all of them are using illegal pesticides, insecticides that are banned in the United States in the European Union. They often are brought in through our southern border, and are highly, highly toxic.”

“For example, we have found several dead black bears – three 400-pound black bears dead just from a tiny amount of these insecticides.”

If you go down to the woods today…

Wengert is the executive director of the Integral Ecology Research Center (IERC), a non-profit group dedicated to the research and conservation of California’s wildlife and ecosystems. She and her colleagues hadn’t planned to take on any criminal drug operations when they started the project in 2004, but it soon became apparent that the illegal cannabis market was one of the biggest threats to the endangered species they were monitoring – species like the fisher, a member of the weasel family native to North America.

“There were a few cases early on,” Wengert says. “We discovered that fishers had died of anticoagulant rodenticide poisoning. It kills by basically bleeding animals to death. And this really surprised us because this is a species that lives in remote forest, far away from humans, and far away from agricultural areas where these rat poisons are generally used.”

“And once we started discussing this with law enforcement, it became clear that there was an issue of illegal cannabis cultivation in our national forests […] and so that opened our eyes to this problem, and this is what we see as a major conservation issue for a lot of forest dwelling species.”

After accompanying law enforcement officers on their raids and cataloging the residues left in and around the grow sites, the IERC team soon had a list of toxic pesticides to cross-reference against any mysterious wildlife deaths. And they found a lot of matches. In a study published in PLoS ONE in 2012, the team documented that 46 out of 58 fisher carcasses had been killed by the anticoagulant rodenticide.

And it wasn’t long before these killer chemicals started appearing in the bodies of other dead animals. Black bears, the northern spotted owl, turkey vultures, grey foxes, bobcats, and mountain lions – the team was soon overwhelmed with carcasses to study.

It’s a grim spectacle, but only the surface damage of the illegal farms. The full extent of the destruction goes much deeper.

“At the same time, all the insecticides and other pesticides being used at these sites are contaminating the water, the soil, and the native vegetation,” Wengert says. “It’s destabilizing the soil structure in these very steep slopes where these growers are cultivating and really enhances erosion into water [sources]. The [sites] are often upstream of rural communities that rely on these rivers and streams as a source of drinking water. So that threat is considerable.”

“Talking about water,” she adds, “we estimate that illegal cultivation just on public lands […] is diverting billions of gallons of water annually.”

“These grow sites are basically stealing [water] from our national forests,” she says. “The amount of water [loss] is devastating, especially if you think about it in terms of where we’re at right now in California, in the midst of a massive drought and probably the worst wildfire season we’ve ever seen.”

Out of the frying pan, into the forest fire

When California voted to legalize recreational cannabis in 2016, the hope was that dangerous illegal grow sites would become eyesores of the past. Five years later, that hope is yet to materialize. It’s estimated that the majority of the state’s cannabis market, perhaps up to 90 percent of it, still remains in the hands of unlicensed businesses.

In many instances, it seems, unregulated cannabis growers have become emboldened and taken advantage of the limited capacity of local law agencies to police illegal farms. Only this October, a county in southern Oregon declared a state of emergency due to the sheer number of illegal cannabis farms in the area. The Jackson County Board of Commissioners said that criminal activity relating to marijuana production had “dramatically increased” since Oregon residents voted to legalize cannabis in 2014, and that its police services and agencies have struggled to investigate many of the sites due to a lack of resources and funding.

When asked whether she thinks California has experienced a similar boom in illegal cultivation, Wengert is inclined to agree.

“Yes, I believe we’ve seen the same thing here as Oregon,” she says. “One prediction that people had when legalization actually was implemented is that we would see a significant decrease in the number of illegal grows on public lands, and we just simply have not seen that.”

“We’ve actually seen an increase in the environmental damage that these grows are exerting on our public lands, meaning they’re using the toxic pesticides in higher quantities and greater frequencies. There may not be more growers out there, but the impacts from a single site, on average, seems to have gotten worse.”

The future may look grim for the wildlife and waters of west coast forests, but at least Wengert, her IERC team, and the US Forest Service officers aren’t going anywhere. And if they can keep chipping away at the illegal growers one site at a time until federal legalization and further regulations and funds arrive, there may be hope yet for California’s endangered species.

“As legalization balances out, hopefully as we see changes, potentially at the federal level, we’ll hopefully see a reduction in the damaging practices that people use,” she says. “But until then, our goal […] is to attempt to document the damage so that we can work as a partner in a force to reclaim the land, […] basically cleaning up all those sites that are so damaging. It’s sort of a Band-Aid on a very large problem in California right now, but it’s what we've got.”

“And I think that will increase public awareness of this issue,” she says. “There will be more and more support for programs that can go in and remove all this damage and trash and refuse from our public lands, at least to get rid of that problem as we move towards a more permanent solution.”

“I mean,” she adds, pausing for thought, “you know, we had high hopes when California legalized it that it [illegal grows] would dissipate. So I don’t want to make any predictions,” she says, a tad forlornly. “We will see.”

This article originally appeared in Analytical Cannabis' Advances in Cannabis Cultivation eBook in December 2021. 

Leo Bear-McGuinness

Science Writer & Editor

Leo joined Analytical Cannabis in 2019. From research to regulations and analysis to agriculture, his writing covers all the need-to-know news for the cannabis industry. He holds a Bachelor's in Biology from Newcastle University and a Master's in Science Communication from the University of Edinburgh.


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