Figuring a single greenhouse that size would hold 80 plants, each using about 5 gallons of water a day, he estimated the operation would consume 2 million gallons of water in the dry season and unleash a torrent of sediment in the wet season.
"There has been an explosion of this in the last two years," Bauer said. "We can't keep up with it."
Every grow has its own unique footprint. Some farmers on private land avoid pesticides and poisons, get their water legally, keep their crops small and try to minimize runoff. Urban indoor growers might not pollute a river, but they guzzle energy. A study in the journal Energy Policy calculated that indoor marijuana cultivation could be responsible for 9% of California's household electricity use. Other producers, like the Mexican drug trafficking groups who set up giant growing operations on public lands next to mountain streams, spread toxins far and wide and steal enough water to run oscillating sprinkler systems.
But it's not just the big criminal groups skirting the rules. Tony LaBanca, senior environmental scientist at Fish and Game in Eureka, said less than 1% of marijuana growers get the permits required to take water from a creek, and those who do usually do so after an enforcement action.
Responsible growers could easily get permits, with no questions asked about what type of plant they're watering, LaBanca said. They just need to be set up to take their water in the wet season and store it in tanks and bladders.
Fish and Game wants to step up enforcement, he said, but the staff is overwhelmed. The agency has 12 scientists and 15 game wardens for the entire four counties on the North Coast, covering thousands of mountainous square miles.
Until the last few years, dealing with marijuana cultivation was usually a minor issue. Now, LaBanca said, it is "triage."
On a recent day, Higley, the Hoopa wildlife biologist, took a reporter and photographer to some of the damage he finds in the most remote mountains, where bears, fishers, martens, rare salamanders and spotted owls live in cloud-mist forests. With his colleague Aaron Pole at the wheel, Higley headed north up the Bigfoot Highway and then up a dirt logging road 13 miles into the snow-peaked Trinities.
They were going to a grow that the sheriff had raided by helicopter in August. Deputies cut down 26,600 plants in eight interconnected clearings along Mill Creek, which flows into the Trinity River.
They parked the truck and started threading down precipitous slopes, through thick wet brush and forest. They stepped over bear scat, slippery roots and coastal giant salamanders.
Crossing a 2-foot-wide creek, they came across a black irrigation line. Vague footpaths emerged, empty Coors cans began glinting in the mud, more water pipes spidered out.
After another 40 minutes, they reached a clearing in the bottom of the canyon -- a field of stumps, holes of dark potting soil and hacked-down stalks of marijuana. Dead gray brush and logs ringed the site. A few heavily pruned trees were left standing, to help mask the marijuana grove from the air.
Deputies had severed the irrigation lines during the August raid, but when Higley returned in September to study the environmental impact, some of the line had been reconnected to sprinklers, and plants had re-sprouted. He saw a wet bar of soap on an upturned bucket and realized workers were hiding nearby.
On this return visit, the site was empty, and Higley started picking through the rubbish. "That's d-CON rat poison right there, 16 trays."
At a dump pile next to the creek, he found propane tanks, more rat poison, cans of El Pato tomato sauce, and empty bags of Grow More fertilizer, instant noodles and tortillas.
A lot of the trash had been removed during the August eradication -- dozens of empty bags accounting for 2,700 pounds of fertilizer and boxes for 10 pounds of d-CON (enough to kill 21 spotted owls and up to 28 fishers), as well as the carcasses of two poached deer and the remains of a state-protected ringtailed cat.
"It wouldn't matter if they were growing tomatoes, corn and squash," Higley said. "It's trespassing, it's illegal and it borders on terrorism to the environment."