Americans’ appetite for marijuana is responsible for a burgeoning pot industry that’s worth billions of dollars in California alone.
New research shows illegal grows using rat poison are also harming northern spotted owls, one of the Golden State’s most iconic creatures.
The research, published in the journal Avian Conservation and Ecology, is the first documented, scientific connection between rat poison black market marijuana growers use to protect their crops and widespread contamination of northern spotted owls, a state and federally threatened species.
Earlier research connected use of rat poison on grow sites to deaths of fishers, deer, bears, foxes and upland game birds.
“I live up here where it is the center of the pot growing world; it is out of control and this paper sort of documents that,” said R.J. Gutiérrez, a bird biologist based in McKinleyville, Calif., who reviewed the paper for publication.
The research provides further evidence that even as the state has moved to legalize marijuana consumption, cultivation by some black market growers who flout environmental regulations remains a problem.
“Smoking marijuana is not necessarily benign, at least from an environmental perspective,” Gutiérrez said.
Even pro-pot advocates are calling for a legalization model that legitimizes and rewards environmentally responsible growers while punishing cultivators who harm wildlife.
“Growing cannabis shouldn’t put you on the other side of the criminal justice system; poisoning owls should,” said Hezekiah Allen, executive director of the California Growers Association.
Evidence of owl poisoning
The research tested owl tissue taken from 2009 through 2013 in Humboldt and Del Norte counties in northwestern California.
That’s where researchers collected bodies of 94 owls. Ten of the birds were northern spotted owls and 84 were barred-owls, a non-protected species of owl that has been usurping northern spotted owl habitat.
Some black market growers use rat poison to prevent rodents from preying on their crops. The practice exposes owls who then prey on the rodents to the poison.
Researchers studied tissue from barred-owls collected as part of a prior, unrelated project. The northern spotted owls were collected opportunistically. Essentially, they were bodies of already-dead owls found during previous owl research.
The study area was on privately held, commercial timberland. The land is in large tracts with restricted access and bordered by public, private and tribal land.
“These removal efforts provide a rare opportunity to collect owl tissues in quantities not normally available, and that would typically take many years to accumulate,” the paper stated.
The results were troubling.
Researchers found rat poison in 40 percent of the barred-owls and 70 percent of the northern spotted owls. Further, the rat poison was so-called “second generation,” a type that’s heavily regulated and not in legitimate use in the area where they collected owls.
Some growers use rat poison to prevent rodents from preying on their crops. The practice exposes owls who then prey on the rodents to the poison.
“It is now ubiquitous,” Mourad Gabriel, lead author of the study and faculty member at the University of California, Davis Wildlife Health Center, said about the ecosystem contamination from marijuana cultivation. “There wasn’t a specific area that led to the exposures. It was universally distributed throughout the landscape.”
Another worrisome aspect of the research: the owls’ habitat was privately owned and controlled timberland with little to no threat of trespass marijuana grows, the term for illegal growing on public land, a problem that plagues California.
Researchers’ models predicted they would find lower contamination rates in owls collected on controlled, timber company land. That assumption held true with the earliest samples collected. But samples collected later showed higher rates.
It led Gabriel to suspect growers converting adjacent forest land for marijuana cultivation, which is now legal under California law with state and local permits but illegal federally, is contributing to the scope of the problem.
“Private land cultivation creates more edge habitat (for rodents),” Gabriel said. “If (growers) are using rodenticide, boom, that is where this additional risk is going to occur.”
Although more research would be needed to document the link.
“However, the few private unpermitted grows I have visited near the study area have raised concerns,” Gabriel said. “For example, if only a fraction of the grows were using rodenticides, then you would still have (thousands) of private grows near the study area (acting) as source points.”
Legalization hasn’t solved the problem
Although marijuana consumption and cultivation have grown more visible in California in recent years, it didn’t become legal for recreational use under state law until Jan. 1. Medical marijuana has been legal in California since 1996.
Marijuana remains illegal under federal law, and U.S. Attorney General Jeff Sessions recently rescinded guidance by the administration of former President Barack Obama to minimize federal intrusion in states that permit it.
The move essentially puts discretion into the hands of federal law enforcement, which could lead to legal problems for growers and users even if they’re following state law.
It doesn’t, however, change the fact that there are tens of thousands of grow sites in California and only a small fraction of those growers registered with the state, which would put them under regulatory oversight.
In Humboldt County alone, there are an estimated 10,000 to 15,000 grows, according to an estimate from the county. Officials estimate permit applications only represent about 8 to 13 percent of total cultivation.
“That is very surprising and concerning and significant,” he said. “Unfortunately, there is a pattern, people want to stay in the black market.”
Federal prohibition is just one disincentive that prevents growers from stepping forward and participating in a transparent, regulated and legal marketplace.
Cannabis industry experts say California’s own regulations provide another disincentive.
Complying with California regulations could cost growers tens of thousands of dollars or more. In addition to fees, any grower who steps under the regulatory spotlight is subject to land use and building code regulations.
It’s a tough sell for growers who already have the connections and expertise to operate in the black market.
“They have been doing it on their own for 40 years,” said Anthony Silvaggio, an environmental sociologist for the Humboldt Institute for Interdisciplinary Marijuana Research at Humboldt State University. “What happens is people don’t even try to come into compliance, they are not even going to take that risk.”
The state is still developing an online tracking system legal growers, sellers and buyers would use to trace the product from origin and ensure it's in legal compliance.
Cathy Mudge, spokesperson for Assemblyman Jim Wood, D-Healdsburg, said as the regulatory structure falls into place it will generate revenue from licensed production and sales and help focus the enforcement spotlight on illegal growing and associated environmental problems.
"Now that people are coming into the light, so to speak … there will be fewer illegal growers and that will allow law enforcement to focus their effort on those folks," Mudge said.
Allen said he's hopeful California's regulators and regulated growers will learn from small, family marijuana operations that are already using drought- and environment-friendly practices to produce a crop that's safe for people and wildlife.
Responsible growers, Allen said, refuse to use harmful poisons.
"Using rodenticide is a worst practice," he said. "It is toxic, it kills your pets, it makes your kids sick. It is just not part of growing on a family farm."
The U.S. Fish and Wildlife Service Arcata and Yreka field offices funded the research.
The California Academy of Sciences and the California Animal Health and Food Safety Laboratory System, which is part of the UC Davis School of Veterinary Medicine, conducted necropsies for the study.
Co-authoring institutions included Green Diamond Resource Company, Hoopa Valley Tribe and Humboldt State University.