On California’s northern coast are three counties that marijuana aficionados call the Emerald Triangle. In their view, the growers there have perfected a strain of cannabis that has high potency and consistently high quality. Result: There are many growers, most tending their crops in remote corners of these mountainous, heavily wooded counties.

This produces serious environmental damage. In Humboldt County where the largest amount of Emerald Triangle marijuana is grown, the sheriff’s office conducted an aerial survey and counted 4,000 visible outdoor grows, nearly all of them illegal. (California was the first of 22 states to permit medical use of marijuana, so some grows were established to serve users who have permit cards.)

The illegal grows are usually carved out of forest land (often national forests or acreage owned by timber companies). Typically, the growers clear-cut the trees on the land they want to use, then bulldoze it to their specifications. Next, they divert a nearby stream to provide the one to six gallons required daily by each plant. They then fertilize the plants, causing runoff. This is followed by a generous dose of rat poison.

The upshot: The U.S. Fish and Wildlife Service a week ago declared that stream diversion by marijuana plantations was robbing the rivers that the streams feed of enough cool water for Coho salmon to breed, thus threatening their survival. California’s north coast is big salmon country, for both sport and commercial fishing. The declaration earned banner headlines in the local press.

This week the USFWS said that it was considering seeking a “Threatened” status for the fisher, a native cousin to the weasel. Many fishers have been dying after ingesting the rat poison put out by marijuana planters.

Disruption of the soil for planting the crop and for cutting roads to some of the remote locations causes runoff that silts the area’s rivers—another preventable threat to the already endangered native salmon and steelhead.

In the area, a multi-agency task force has raided, on average, one marijuana plantation a week since January 2013. The biggest one, in August this year, yielded 10,000 plants; most have had several hundred. The plants are destroyed. The “harvest” often yields cash, weapons, and, sometimes other drugs (although multi-drug hauls tend to found in in-town dealer houses).

In addition to the cost of the raids, “grows” on public land require public resources to clean up and restore the affected area.

Environmentalists in the three counties are quick to run to the battlements and declare all-out war any time the state Transportation Department sets out to widen a highway. With the regular pot plantation raids, however, they are as silent as mice. Occasionally, one will opine in an interview that the problem would go away if marijuana were made legal. This outcome seems unlikely. Large companies might buy up some tracts for growing (along with getting the necessary permits and paying taxes); however, not every small grower will be able to compete; hence, the likelihood they would feed a black market, selling to heavy users at below-market prices. Thus, one problem would yield to another.