In November 2016, California legalized recreational marijuana. The decision, supported by 56 percent of the state’s voters, allows marijuana to be shared, traded, grown at home and smoked without a medical reason. Using it medically has been legal for 20 years.

Though complex and strict regulations still apply to growing, selling and buying marijuana, things will probably simplify over the next year. The heart of the state’s industry has long been in the north coast region known informally as the emerald triangle. Most growers – thousands of them in the heavily wooded counties of Humboldt, Trinity and Mendocino – currently operate illegally. However, many are now lining up at county offices to apply for cannabis production permits, and conservationists, growers and scientists are asking how the new era of pot production will affect the environment.

It may have positive effects. For instance, a grower seeking a commercial production permit must install a water storage system that can be filled in the wet winter season. Such a system would allow growers to keep plantations lush and green all summer without drawing water from creeks, which can easily be pumped dry during California’s hot and mostly rainless summers.

Mikal Jakubal, a Humboldt County resident who has grown marijuana for years at his residence alongside a tributary of the Eel River called Redwood Creek, believes cannabis can be grown sustainably, by capturing and storing water in the winter and minimizing the erosion from earth-moving activities such as building roads and clearing land to plant. Sediment that washes into creeks can smother the gravel beds where adult salmon and trout spawn, killing the unborn fish.

But Jakubal suspects many growers who apply for permits might make the required improvements only temporarily, reverting to less sustainable – and illegal – activities once they are on the books as legal growers.

“There is minimal ability to enforce standards beyond the initial inspection,” he says. “That’s just the reality. If you have hundreds or thousands of growers, all up dirt roads behind locked gates, and [authorities] have to give them advance notice of any site visit, it’ll be super easy to save your stored water, pump out of the creek all summer and then keep your tanks as back-up.”

Scott Bauer, a senior environmental scientist with the California Department of Fish and Wildlife, promises his department will be on close watch.

“The paperwork of getting permits is not just a formality,” he says. “You have to abide by it and we’re going to be checking on people. Someone who doesn’t follow the rules could lose their permit and would have to start over.”

Humboldt County’s planning and building department has received more than 2,300 applications for new growing permits since the November election. Already, the forests of the county may support somewhere between 8,000 and 10,000 pot growers, according to rough estimates.

The stress on the environment generated by cannabis farming has long been discussed by media and scientists, and while it is generally agreed that pot growing isn’t helping water resources or fish, no one is certain how harmful the industry actually is.

“It’s really important that the state regulates the industry, but it’s also important not to take our eye off the ball,” says Van Butsic, a researcher with University of California, Berkeley’s Department of Environmental Science, Policy and Management. “The north coast’s salmon were mostly gone long before cannabis got here, and you’re not going to get them back by regulating it.”

Other impacts must be mitigated, too, he says; logging, dams, riverside development and large-scale public water diversions have all had great impacts on salmon runs.

Still, there is no doubt pot growing is having an impact on what remains of the region’s salmon runs. Bauer says he has seen streams that should have had water in them but had been emptied by just one grower’s irrigation line.

“A lot of these growers are diverting straight from the headwaters of small creeks that are the beginnings of our larger rivers, and we’ve seen them pumping these little streams dry,” he says. “Sometimes it’s one grower doing it, other times it’s 10 of them along a whole stream.”

Scott Greacen, executive director of Friends of the Eel River, is convinced new pot-growing operations, legal or not, will worsen conditions for fish in places.

“How many regulated operators can you have along Redwood Creek and still have coho salmon in it?” says Greacen, referring to the Eel’s south fork tributary alongside which Jakubal, for one, grows his marijuana

California is the fifth state to legalize recreational pot, and it was the first state to legalize medical marijuana in 1996. Most growers in California operate at small production levels, often on rural mountain homesteads, and often using organic growing methods.

But Greacen discounts popular notions that pot is a low-impact crop. “All the talk about how this is a sustainable industry – it just doesn’t add up,” he says.

Butsic coauthored a paper published in 2016 in Environmental Research Letters in which he concluded that the legal marijuana industry poses a considerable potential threat to Chinook salmon and steelhead in the emerald triangle region.

Greacen says many northern California populations of coho and Chinook salmon and steelhead trout were barely clinging to existence in the years leading up to the drought, and the recent surge in marijuana growing activity has wiped them out. “This is what the process of extinction looks like. It’s really scary.”

Jakubal argues that the marijuana industry’s environmental problems are ultimately the result of economics – not necessarily anything fundamentally unsustainable about the crop. In the interest of healthy waterways, he says, pot must become cheap through widespread production and, probably, federal legalization.

“As long as it’s profitable, greedy people will do whatever it takes to make that money,” he says.

Butsic reckons the jury is still out on just how harmful the marijuana industry is to the environment – an area of research he says he is closely studying. But Greacen feels more certain that fish and pot cannot coexist under current circumstances.

“Maybe making Humboldt County the epicenter of legal weed isn’t the best idea if we also want to have salmon in our rivers,” he says.

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