Pesticide bottle at pot grow
Mexican pesticide bottles at an illegal marijuana growing site.

Fishers are small meat eaters that live in remote areas of our national forests from Oregon to California. They can climb trees and belong to the same family as weasels and wolverines.  The fisher was also the first clue for U.S. Forest Service wildlife ecologist Mourad Gabriel in helping unravel the mysterious poisoning of northern spotted owls.

His team would discover that both the fishers and the owls are being exposed to deadly pesticides meant to kill rodents feeding on marijuana plants found in pot fields scattered across the state. The supposition is that both the fishers and owls are feeding on rodents contaminated by the chemicals.

“Poisons found in the rodents are contaminated. And the owls utilize these cultivation sites for foraging activities,” said Gabriel. The application of these poisonous chemicals pollute streams, soil and kill wildlife.

A recent report issued by Gabriel and other researchers found that “Illegal cannabis cultivation on public lands has emerged as a major threat to wildlife in California and southern Oregon due to the rampant use of pesticides, the destruction of the habitat and water diversions associated with trespass grow sites.”

The report noted that “cannabis cultivation seems to have increased rapidly in the western United States in the past decade,” although this may be due to increased awareness of the issue. More than 80% of fishers within the study region were found to have pesticides in their tissues as well as 70% of the spotted owls.

The marijuana plants  are found in large and growing sites in national forests in Southern California and elsewhere. Gabriel said our nearby national forests — Cleveland, Angeles, San Bernardino,  Los Padres, Sequoia — “are inundated with cultivation sites.”

California fisher
A California fisher. Courtesy Morgan Heim

The  pesticides are smuggled into the United States across the border from Mexico, said  Assistant U.S. Attorney Melanie Pierson, who is prosecuting smugglers bringing their deadly cargo over the border. “These are very dangerous to wildlife, they go up the food chain,” she said.

The growers, she said, “use zinc phosphide to kill rats because rats like to eat the marijuana plants. And then what happens is an owl will eat the rat. They are in the class of neurotoxins that originally were designed to be chemical-warfare weapons.” 

According to Department of Justice research, “ingestion of seven drops to one teaspoon of zinc phosphide would likely kill a 150-pound person.”

Eight years ago in Riverside County, nine investigators from the Riverside County Sheriff’s Department and members of the U.S. Forest Service were removing plants from an illegal pot grow, unaware they were releasing deadly chemicals into the air. They were all hospitalized.  It was found the pesticides enter the lungs through inhalation or through the skin by coming into contact with the chemicals.  

Pierson said the Environmental Protection Agency, Homeland Security, Forest Service and California Department of Toxic Substances Control have been stepping up their crackdown on smuggling of the deadly pesticides. This initiative began after the Riverside incident involving law enforcement personnel. 

Northern spotted owl
A northern spotted owl. Courtesy Redwood national and state parks

Since then Border Patrol agents have been trained to be on the watch for the illegal pesticides. As of July, the increased attention to smuggling has resulted in the prosecution of 50 defendants for environmental crimes and the seizure of some 1,000 containers of illegal Mexican pesticides.

A key member of the joint federal  effort is Homeland Security, which is utilizing training provided by agents from the EPA on what to look for on Spanish-language labels and containers. “The trick of this is that they’re concentrated volumes,” said Ernest Verina, assistant special agent in charge or Homeland Security investigations. “And that means “smaller amounts yield greater results in the application.” 

Verrina said that while border agents are trained on finding all sizes and types of items, these pesticides are a special challenge. They are hidden in purses, and the smugglers also use “deep concealment” practices like behind the quarter panels of vehicles and in hidden compartments of luggage. 

10News on Thursday reported on the stepped up efforts to halt the smuggling.

Gabriel said his research into the problem began in 2009 “when  we had our first fisher that died from rodenticide.”  It was of concern because the fishers live deep in forests and not near populated urban areas.  What could be killing the fisher so far from most human activity, researchers wondered.

“It’s something that shouldn’t have happened,” Gabriel said. “It’s like an individual drowning in the middle of the Mojave Desert and there’s no water around.  It took three more years to compile the data to show this was not a one-time occurrence.”

“This is not just one forest or one area, this is California and potentially a national public land concern,” he added, and since the discovery of the source of the die-offs, “it’s continued to grow into an even bigger issue.”

Gabriel noted that contamination lingers for the affected animals. Even if the contamination was last year, an owl can transfer poison to its offspring. He said there are two different types of pesticides used, one to eliminate the rodent population and another — carbofuran — “to kill the spider mites that  really damage the cannabis plants out in these remote  settings.”

According to Pierson, in one study, “the pesticide transfer rate of carbofuran into cannabis smoke from glass pipes was as high as 70% into the pot smoker’s bloodstream.”

The profit motive drives these dangerous practices. For the pot growers it’s more marijuana to sell; for the pesticide smugglers it’s “very lucrative,” Pierson said. “These banned pesticides are purchased by smugglers in Mexico and sold under various trade names. You can buy a one-liter bottle in Mexico of these chemicals for about $10 and sell it up here for somewhere from $130 to $250 for that same bottle.”

Gabriel said a solution is at hand if an effort is undertaken to make it tougher on the drug traffickers and their hired hands.

“One hundred to 200 sites are reoccurring every year. A lot of that is because the infrastructure still there — it’s easy for somebody to just come back out to the grow,”  Gabriel said. He added that they “reconnect the (water) pipes, and then you get a grow site reestablished.”  

He suggested cleaning up the marijuana sites, removing all the infrastructure, and leaving only the dirt that was originally there.

JW August is a San Diego-based broadcast and digital journalist.