This story first appeared on Mother Jones and is reproduced here as part of the Climate Desk collaboration.

Starting about 90 miles northwest of Sacramento, an unbroken swath of national forestland follows the spine of California's rugged coastal mountains all the way to the Oregon border. Near the center of this vast wilderness, along the grassy banks of the Trinity River's south fork, lies the remote enclave of Hyampom (pop. 241), where, on a crisp November morning, I climb into a four-wheel-drive government pickup and bounce up a dirt logging road deep into the Six Rivers National Forest. I've come to visit what's known in cannabis country as a "trespass grow."

"This one probably has the most plants I've seen," says my driver, a young Forest Service cop who spends his summers lugging an AR-15 through the backcountry of the Emerald Triangle—the triad of Humboldt, Mendocino, and Trinity counties that is to pot what the Central Valley is to almonds and tomatoes. Fearing retaliation from growers, the officer asks that I not use his name. Back in August he was hiking through the bush, trying to locate the grow from an aerial photo, when he surprised a guy carrying an iPod, gardening tools, and a 9 mm pistol on his hip. He arrested the man and alerted his tactical team, which found about 5,500 plants growing nearby, with a potential street yield approaching $16 million.

Today, a work crew is hauling away the detritus by helicopter. Our little group, which includes a second federal officer and a Forest Service flack, hikes down an old skid trail lined with mossy oaks and madrones, passing the scat of a mountain lion, and a few minutes later, fresh black bear droppings. We follow what looks like a game trail to the lip of a wooded slope, a site known as Bear Camp. There, amid a scattering of garbage bags disemboweled by animals, we find the growers' tarps and eight dingy sleeping bags, the propane grill where they had cooked oatmeal for breakfast, and the backpack sprayers they used to douse the surrounding 50 acres with chemical fertilizers and pesticides. The air smells faintly of ammonia and weed. "This is unicorns and rainbows, isn't it?" says Mourad Gabriel, a former University of California-Davis wildlife ecologist who has joined us at the site, as he maniacally stuffs a garbage bag with empty booze bottles, Vienna Beef sausage tins, and Miracle-Gro refill packs.

According to federal stats, trespass grows in California alone account for more than one-third of the cannabis seized nationwide by law enforcement, which means they could well be the largest single source of domestically grown marijuana. Of course, nobody can say precisely how much pot comes from indoor grows and private plots that are less accessible to the authorities. What's clear is that California's marijuana harvest is vast—"likely the largest value crop (by far) in the state's lineup," notes the Field Guide to California Agriculture. Assuming, as the guide does, that the authorities seize about 10 percent of the harvest, that means they would have left behind more than 10 million outdoor plants last year, enough to yield about $31 billion worth of product. That's more than the combined value of the state's top 10 legal farm commodities.

Even before voters in Colorado and Washington legalized recreational pot in 2012, marijuana was quasi-legal in California, and not just for medical use. Senate Bill 1449, signed by Gov. Arnold Schwarzenegger in 2010, reclassified possession of an ounce or less from a misdemeanor to a maximum $100 infraction—you'll get a bigger fine for jaywalking in Los Angeles. Indeed, many states have eased restrictions on pot use. But with the exception of Colorado and Washington, whose laws dictate where, how, and by whom marijuana may be grown, they have had little to say about the manner in which it is cultivated—which is challenging to dictate in any case, since growers who cooperate with state regulators could still be prosecuted under federal statutes that classify pot as a Schedule 1 drug, the legal equivalent of LSD and heroin. So where is all this legal and semilegal weed supposed to come from? The answer, increasingly, is an unregulated backwoods economy, the scale of which makes Prohibition-era moonshining look quaint.

To meet demand, researchers say, the acreage dedicated to marijuana grows in the Emerald Triangle has doubled in the past five years. Like the Gold Rush of the mid-1800s, this "green rush," as it is known locally, has brought great wealth at a great cost to the environment. Whether grown in bunkers lit with pollution-spewing diesel generators, or doused with restricted pesticides and sown on muddy, deforested slopes that choke off salmon streams during the rainy season, this "pollution pot" isn't exactly high quality, or even a quality high. "The cannabis industry right now is in sort of the same position that the meatpacking industry was in before The Jungle was written by Upton Sinclair," says Stephen DeAngelo, the founder of Oakland's Harborside Health Center, a large medical marijuana dispensary. "It simply isn't regulated, and the upshot is that nobody really knows what's in their cannabis."

It's not just stoners who are at risk. Trespass grows have turned up everywhere from a stand of cottonwoods in Death Valley National Park to a clearing amid the pines in Yosemite. "I now have to spend 100 percent of my time working on the environmental impacts of marijuana," says Gabriel, who showed up at Bear Camp in military-style cargo pants and a kaffiyeh scarf. "I would never have envisioned that."

Gabriel grew up in Fresno, the son of immigrants from Mexico and Iraq, at a time when the Central Valley city was plagued by turf wars among pot-dealing street gangs, notably the local Norteños chapter and their rivals, the Bulldogs. That world did not interest Gabriel, who spent a lot of his free time catching frogs and crawdads on the banks of the San Joaquin River. His love of the outdoors led him to study wildlife management at Humboldt State University, where he became fascinated with fishers, the only predators besides mountain lions clever and tough enough to prey on porcupines. The fisher, which resembles the love child of a ferret and a wolverine, was nearly eradicated from the West by logging and trapping during the early 20th century. It still hasn't rebounded. This year, the US Fish and Wildlife Service will consider listing it as a threatened species.

When Gabriel first began venturing into the woods to trap and radio-collar fishers, he assumed that most of them were dying from bobcat attacks, disease, and cars running them over. But then, in 2009, he discovered a dead fisher deep in the Sierra National Forest that showed no signs of any of those things. A toxicology test indicated that it had ingested large quantities of rat poison.

Back in his lab, he tested frozen tissue from 58 other fisher carcasses he'd collected on some of California's most remote public lands and found rodenticide traces in nearly 80 percent of them. Rat poison isn't used in national forests by anyone except marijuana cultivators, who put it out to protect their seedlings. Rodents that eat the poison stumble around for a few days before they die, making them easy prey for hungry fishers.

In 2012, after Gabriel published his rat poison results, he was the target of angry calls and messages. One person accused him of helping the feds "greenwash the war on drugs." Another made vague threats against his family and his dogs. Gabriel also received a prying email, later traced by federal agents to Ciudad Juárez, Mexico, soliciting the locations of his home, office, and field study sites. In Lost Coast Outpost and other local news sites, commenters shared links to his home address. "Snitches end up in ditches," one warned.

Then, last month, Gabriel's Labrador retriever, Nyxo, died after someone fed him meat infused with De-Con rat bait.

The types of threats Gabriel has received are not uncommon, and they have frightened scientists away from studying the environmental impacts of pot farming. "At my university, there is nobody who will even go near it," says Anthony Silvaggio, a sociologist with the state university's Humboldt Institute for Interdisciplinary Marijuana Research. Biologists who used to venture into the wilderness alone to survey wildlife now often pair up for protection. In July 2011, armed growers in the Sequoia National Forest chased a federal biologist through the woods for a half-hour before giving up. The following year, researchers surveying northern spotted owls on Humboldt County's Hoopa Valley Indian Reservation were shot at with high-caliber rifles. Each growing season, a significant chunk of one designated fisher habitat in the Sierra National Forest becomes inaccessible to scientists because it's dangerously close to illegal gardens.

Gabriel won't go near a known grow site before it's been cleared by law enforcement, as Bear Camp has. Scattered across the hillside, his team finds 4,200 pounds of chemical fertilizer, five kinds of insecticide, and three kinds of rodenticide. The stash includes a restricted pesticide capable of killing humans in small doses. Gabriel's friend and colleague Mark Higley dons a gas mask and seals the canister in a garbage bag. "If it does erupt, I want everyone to be at least 20 to 30 feet away," Gabriel warns. "It's aluminum phosphide, and when it hits the air, it turns into phosphine gas." Breathing it can kill you.

The Emerald Triangle's pot culture has changed a lot since the hippies drove up from San Francisco in the early 1970s in search of peace, freedom, and blissful communion with nature. At first, the back-to-the-landers grew pot primarily for themselves, but news that the United States was paying to have Mexican pot farms sprayed with paraquat, a toxic weed killer, convinced American stoners to seek out the hippie weed.

Before long, Humboldt had become a name brand, but marijuana might never have come to define the Emerald Triangle had the old-growth timber industry not logged itself out of business by the mid-1990s. In 1996, when California became the first state to legalize pot for medical use, out-of-work loggers took advantage of the opportunity. "Then you had everybody like, 'Sure, I'll grow some weed,'" recalls Humboldt State's Silvaggio. The size of the harvest grew, helped along by post-9/11 border enforcement, which made it harder for Mexican pot to enter the country. The latest leap in production was the result of Prop. 19, California's 2010 legalization measure; although it lost narrowly at the polls, the Emerald Triangle's growers boosted output in anticipation of having a mainstream product. Now marijuana "is all we have," Silvaggio says. "Every other thing is built here to serve that economy."

Drive around the Emerald Triangle during harvest season with the radio on, and you'll hear ads openly pitching Dutch hydroponic lamps, machines "for trimming flowers," and 2,800-gallon water storage tanks—because "you don't want to be the one that has to call the water truck in for multiple water deliveries late in the season." Even mainstream businesses like furniture stores get in on the green rush with "harvest sales." Talk of bud-trimming parties and the going price per pound dominates restaurant conversations. And in backwoods hamlets where you'd expect high unemployment, you come across a lot of $50,000 pickups.

As with much of the state's agricultural industry, the pot trade is stratified, and much of the labor is done by undocumented farmworkers. The man arrested at Bear Camp confessed to the police that he'd traveled north from Michoacán, Mexico, to pick apples in Washington, but knew he could make more money tending pot in California. Industry observers believe that at least some of the trespass grows are run from south of the border, but Silvaggio adds that many are financed by locals. Either way, the grunt workers tend to be the only ones busted when the grows are raided.

Although the original Northern California growers saw pot cultivation as an extension of their hippie lifestyles, their environmental values haven't readily carried over to the next generation. "They are given a free pass to become wealthy at a young age, to get what they want," Silvaggio explains. "And do you think they are going to give it up when they turn 20, with a kid in the box? They can't get off that gravy train." But with prices dropping as domestic supply expands, "you can't go smaller; you've got to go bigger these days to make the amount of money you used to make. So what does that mean? You have to get another generator. You have to take more water. You've got to spray something because you may lose 20, 30 grand if you don't."

Smaller growers operating on their own properties tend to use slightly better environmental practices— avoiding rodenticides, for instance—than the industrial growers who have moved in solely to make money. Even so, Silvaggio says, "we found that it's just a tiny fraction of folks who are growing organic."

Among the downsides of the green rush is the strain it puts on water resources in a drought-plagued region. Scott Bauer, a biologist with the state Department of Fish and Wildlife, calculates that irrigation for cannabis farms has sucked up all of the water that would ordinarily keep local salmon streams running through the dry season. Marijuana cultivation, he believes, "is a big reason why" at least 24 salmon and steelhead streams stopped flowing last summer. "I would consider it probably the No. 1 threat" to salmon in the area, he told me. "We are spending millions of dollars on restoring streams. We are investing all this money in removing roads and trying to contain sediment and fixing fish path barriers, but without water there's no fish."



Thirty square miles in one Emerald Triangle watershed, where pot farms siphon up roughly 29 million gallons of water per season Source: California Department of Fish and Wildlife.

At Bear Camp, Gabriel leads me to a steep slope where the growers have plugged a freshwater spring with a makeshift dam of logs and tarps, one of 17 water diversions found at the site. Where moisture-loving ferns and horsetails should be flourishing, a plastic pipe leads downhill to a 1,000-gallon reservoir feeding a vast irrigation network. Gabriel unkinks a hose to release an arc of water from a sprinkler. National Guard troops enlisted to help out have already yanked the cannabis plants here, leaving behind a hillside of girdled white oaks and bare soil. "When we have a two-to-four-inch rain, this will just be a mud river," Gabriel says. Sediment laced with pesticides and other chemicals will find its way into the salmon stream below. We hike down to a clearing where a helicopter is pulling out sling loads of irrigation piping. "Look at this!" Gabriel shouts after plunging into a thicket to help the soldiers rip out another dam. "Insect killer right in the middle of it!"

He and his colleagues have seen much worse. At a grow site in July, he found a fisher that had died from eating one of many poisoned hot dogs strung around the site on a trotline. A state game warden raiding a grow in 2011 discovered a black bear and her cubs convulsing on the ground, having eaten into a stash of pesticides. Two threatened northern spotted owls, the species once at the center of a bitter fight between loggers and environmentalists, tested positive for rodenticides in Gabriel's lab; he's now looking into whether toxins from grow sites could be impeding that species' recovery as well. "When there is no adequate regulatory framework," Silvaggio warns, "you are going to have nature taking a hit."

Most growers just want to be left alone, but the small minority who are politically outspoken tend to favor regulation. Kristin Nevedal chairs the Emerald Growers Association, the triangle's marijuana trade group. The coauthor of an ecofriendly pot-farming guide, she often consults with state and local lawmakers about how to make the industry more responsible. "Prohibition hasn't curbed the desire for cannabis," she says. "So we really need to look at changing our policy and starting to treat it like agriculture, so we can manage it."

One of the most serious efforts on that front was a system put in place by Mendocino County, which as of 2010 allowed the cultivation of up to 99 plants, provided growers registered and tagged each one with zip ties purchased from the county. Sheriff's deputies monitored the grow sites and checked that they complied with environmental laws. "That program was in a lot of ways fabulous," Nevedal recalls. Almost 100 growers participated, but the program was shut down in early 2012, after federal agents raided one of the grows and US Attorney Melinda Haag hinted that she might just take the county to court. Later that year, a federal grand jury subpoenaed the county's zip tie records.

Since then, efforts to regulate pot farming have mostly shifted to the state level. In Colorado, pot vendors are required to list on their packaging all the farm chemicals used to produce their products, and the state recently implemented a "seed to sale" tracking system. Most Coloradans grow indoors due to the climate, which reduces pesticide use and makes it easier to keep pot off the black market, but it's highly energy intensive. In the journal Energy Policy, researcher Evan Mills estimated that indoor grows suck up enough electricity to supply 1.7 million homes—in California, they account for a whopping 9 percent of household energy use. The newly minted regulations for Washington state allow outdoor grows so long as they are well fenced and outfitted with security cameras and an alarm system.

In the next few years, new legalization measures appear destined for the ballot in California, Alaska, and Oregon. But while it may help create a market for responsibly grown cannabis, legalizing pot in a few states won't wipe out the black market, with its steep environmental toll. There's simply too much money to be made shipping weed to New Yorkers at $3,600 per pound, and too few cops to find all the grows and rip them out. "The trespass grows are really an issue because of prohibition," says Gary Hughes, the executive director of the Environmental Protection Information Center, a 37-year-old Emerald Triangle environmental group that cut its teeth fighting the logging industry. "It is not the growers who are a disease. They are just a symptom. The real disease is the failed drug war."

Yet without the drug war, the region's pot sector might fade into oblivion. Take away the threat of federal raids, and to some extent pot becomes just another row crop, grown en masse wherever it's cheapest. "A shift in cultivation to the Central Valley is definitely possible," Hughes acknowledges.

There will likely still be a niche for the Emerald Triangle growers who started it all, Nevedal believes, just as there has been for craft whiskey distilleries in post-Prohibition Kentucky. Growing really good weed is simply too much work and too much strain on the environment to make sense on an industrial scale. As it happens, Nevedal speculates, the Emerald Triangle might just end up where it started, providing artisanal dank for a high-end market. "The future," she says, "is the small family farm."