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By Sara Merken
Unpermitted rat poisons used by illegal marijuana growers in California endanger owls and other wildlife, but state officials hope the recent move to legalize the drug will see more growers comply with pesticide regulations.
While legal cultivators can expect more government oversight, environmental researchers fear the increase in the number of growers will include illegal operations that won’t apply for permits to use rat poisons, or rodenticides. That has led environmental advocates to call for increased enforcement on pesticide use and even a statewide ban on all rat poisons.
Seventy percent of northern spotted owls and 40 percent of barred owls tested positive for rodenticides in northwest California in a recent study conducted by the University of California, Davis and the California Academy of Sciences. Northern spotted owls are threatened species under the federal and state endangered species laws.
The authors of the study said private timberland is increasingly being turned into illegal marijuana farms, which often overlap with designated owl habitats. Owls that feed on these lands can consume poisoned rats and move the pesticide through the food chain.
The rodenticides used on illegal marijuana sites have “gone through and infiltrated the food web profusely” in addition to contributing to soil and water contamination, Mourad Gabriel, lead author of the report and research faculty member with University of California, Davis’s Wildlife Health Center, told Bloomberg Environment.
Gabriel, also the executive director of Blue Lake, Calif.-based nonprofit Integral Ecology Research Center, published research in 2012 and in subsequent years that linked anticoagulant rodenticides on illegal marijuana farms to deaths of Pacific fishers, which are weasel-like mammals that live in forests in Northwest California.
The California Department of Pesticide Regulation has taken steps to make the most potent rat poisons less accessible to consumers.
The agency restricted public access to some of the materials to allow only licensed exterminators to use the products in July 2014. However, environmental advocates say more can be done.
State efforts to legalize cultivation and recreational use of marijuana are part of a “larger agenda, which is to get the illegal cannabis growers into a legal licensed arena,” Jesse B. Cuevas, assistant director of the department’s Pesticide Programs Division, told Bloomberg Environment.
“What we anticipate is that a lot of those illegal grows will actually turn into legal grows that we can then regulate and help to clean up the environmental harm that has been caused by illegal uses of pesticides,” Cuevas said.
The California Department of Food and Agriculture “has received thousands of applications for cannabis cultivation licenses and cannot speculate about the number of illegal grows in the state,” a department spokesperson told Bloomberg Environment in an email.
Rat poisons are typically anticoagulants, which cause clotting problems and internal bleeding. Second-generation anticoagulants are highly potent and can kill rodents with a single feeding, while first-generation poisons still pose a risk to wildlife but don’t always have an immediate effect.
“These type two anticoagulant rat poisons should probably be prohibited entirely. I don’t really see this as a cannabis issue so much as a rat poison issue,” Hezekiah Allen, executive director of the California Growers Association, a Sacramento-based group that represents cannabis growers, told Bloomberg Environment.
Legal growers don’t typically use those rodenticides because of their toxicity, Allen said.
Legislation is pending in the California legislature to ban all anticoagulant rodenticides in the state. AB 1687 stalled in the state assembly’s Environmental Safety and Toxic Materials Committee last year. Advocacy groups, including Berkeley-based Raptors Are the Solution (RATS), are pushing for the passage of the bill to further restrict second-generation anticoagulants.
“We probably won’t get all poisons banned, but it’s a starting place,” Lisa Owens Viani, director of RATS, told Bloomberg Environment.
Representatives of the pesticides industry could not be reached for comment.
The Pest Control Operators of California opposed the bill in the group’s 2017 legislative agenda, saying the bill is “reckless and ill conceived.” The group represents about 1,100 operators in the state.
“This ban would take away one of the most important management tools for this pest with no regard for the consequences,” the agenda said. “PCOC has made significant efforts to improve the selection and use of these products and continues to stand ready to work with all groups to improve the education of users of rodenticides and the enforcement of established regulations.”
While the state considers a ban, the California Department of Fish and Wildlife, which enforces pesticides regulations, has increased staff and resources on its Marijuana Enforcement Team and its Watershed Enforcement Team to address marijuana enforcement in the past few years, Capt. Patrick Foy from the department’s Law Enforcement Division, told Bloomberg Environment.
The strategy going forward will include raids on illegal grows and remediation of the land, he said.
Though state officials hope legalization will bring more growers into compliance with pesticide regulations, report author Gabriel said quick action is needed.
“Can the environment wait three, five, eight years until the black market dissipates, when we already have clear empirical evidence that we have food web contamination?” Gabriel asked.
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