From using an obscene amount of water to poisoning local wildlife to hampering a fish rehabilitation project, the practice of farming marijuana is taking its toll on the environment. And environmentalists are not pleased.

According the Los Angeles Times, a study conducted by state scientists evaluating a 37-square-mile area yielded in 281 outdoor pot farms and 286 greenhouses with an estimated total of 20,000 plants. To grow this many plants, the scientists estimate that it takes 18 million gallons of water each year from the local watershed. The study area was off of a tributary of the Eel River near Eureka, Calif., where scientists are trying to rehabilitate coho salmon and other threatened fish species.

Studies Find California Marijuana Farming Adds Up to Negative Environmental Effects

(Photo: RAUL ARBOLEDA/AFP/Getty Images)

“That is just one small watershed,” Scott Bauer, a scientist leading the coho recovery on the North Coast with the state’s Department of Fish and Game, said according to the L.A. Times. “You extrapolate that for all the other tributaries, just of the Eel, and you get a lot of marijuana sucking up a lot of water.… This threatens species we are spending millions of dollars to recover.”

It’s not just these species that are suffering, though. The L.A. Times reported that a University of California-Davis study found 46 out of 58 carcasses of a rare forest animal called a fisher, which it describes as a carnivore and weasel-like, in the study area had rat poison in their system. The study authors said they believe the pesticide is being mixed with some fish products to kill bears and other animals who enter the marijuana farms.

Other chemicals and herbicides have been found leaking into the local watershed allegedly from marijuana farms as well. Excess fertilizers in the past decade have also contributed to toxic algal blooms.

Studies Find California Marijuana Farming Adds Up to Negative Environmental Effects

(Photo: RAUL ARBOLEDA/AFP/Getty Images)

Bauer with the state DFG said the growers don’t really understand how they’re influencing the environment.

“I started talking to this guy, and he says he used to be an Earth First! tree-sitter, saving the trees,” Bauer said, according to the L.A. Times. “I told him everything he was doing here negates everything he did as an environmentalist.”

Some growers, the L.A. Times reported, cultivate the plants legally and safely in the state with the proper procedures and permits, but not all. The Times stated that much of problem comes from marijuana growing being unregulated in California.

Read more details of the destruction some marijuana growers are unleashing on the environment in the L.A. Times report here.

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