There’s a harsh downside to the boom in marijuana legalization and use on the West Coast: Illegal growers are polluting the environment to an alarming degree and threatening the health of people and rare wildlife in the process.
Mourad Gabriel, an ecologist with the Integral Ecology Research Center in northwest California, told Reuters the problem is much worse than researchers and officials previously thought. He estimates illegal marijuana sites on federal land in California—where most of these pot-growing farms are found—contain 731,000 pounds of solid fertilizer, 491,000 ounces of concentrated liquid fertilizer and 200,000 ounces of toxic pesticides. This waste is potent enough to harm law enforcement officials investigating the crops; contact with these toxic materials during raids or searches of illegal marijuana farms has sent at least five officials to the hospital for skin rashes and trouble breathing, according to Reuters.
The waste also isn’t being properly treated. Gabriel, who has visited about 100 of these locations, says that when state remediation officials come to clean up, they often don’t do a thorough job, as many of the sites still contain as much as half the original waste.
Several studies suggest waste from these marijuana operations can hurt rare animals. For example, research by Gabriel’s team found that 10 percent of dead fishers, a weasel-like mammal found in California, were killed by rodenticide poisons that are often stocked at marijuana farms to reduce mice populations. These toxic chemicals are scattered about the farms to prevent vermin from disturbing cannabis plants, but they end up accidentally poisoning other animals. Some fishers were found with up to six poisons in their systems, suggesting that the scale of the contamination is quite serious.
These toxic substances are likely affecting many other animals as well. Fishers “may be our ‘canaries in the coal mine,’” Bill Zielinski, a researcher with the Forest Service’s Pacific Southwest Research Station, told Newsweek for a previous story. “I worry that with the density of grow sites on public lands in California, that entire biological communities may be affected,” including land and aquatic wildlife, he said. Preliminary research suggests poison from these farms may also be killing spotted and barred owls in California after they eat poisoned rodents.
Besides the use of toxic agricultural chemicals, marijuana cultivation also requires large amounts of water—twice that used for growing wine grapes, for example. According to a 2015 study in PLOS One, illegal grow sites in northwest California divert almost one-quarter of the regional water flow in their watersheds. That paper also found high levels of fertilizers, pesticides, herbicides and fungicides in runoff from marijuana operations.
The scale of the problem remains little-known and under-studied, in part due to marijuana’s murky legal status. Now that all three West Coast states have legalized the plant, officials hope that more growers will follow legal limits on pesticides, fertilizers and the like, and ceasing farming on public lands. California’s State Water Resources Control Board has begun the public review period for laws that “protect surface and groundwater supplies from pollution generated by legal cannabis farming,” KEYT, the Santa Barbara ABC affiliate, reported. "We have anecdotal stories and evidence of just buckets of stuff just being dumped into streams killing fish, poisoning the water,” Felicia Marcus, with the board, told the publication. She added that she hopes that will cease “with more people coming into the fold” to legally grow cannabis, and the organization anticipates putting the regulations going into effect by November.
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