Global warming may give a minor twist to that classic hippie bumper sticker that quips “Acid rain: Too bad it’s not as much fun as it sounds.” Turns out a warming climate could boost the medicinal and psychoactive properties of plants including cannabis.

But that’s not all: Climate change will also open up higher elevations to growing weed clandestinely on public lands, a practice that’s putting increased strain on fragile ecosystems. Some say relaxed marijuana laws exacerbate the problem by bringing in more growers; others argue increased regulation and oversight will eventually lead to more responsible growing practices.

One prominent researcher who specializes in weed migration patterns in the face of climate change said marijuana grown outdoors will likely become stronger and require less water to thrive.

“If you go back to the times plants evolved on land, the average CO2 (carbon dioxide) levels were 1,000 parts per million; today it’s about 400,” said Lewis Ziska, a plant physiologist with the U.S. Department of Agriculture’s Agricultural Research Service.

About 4 percent of plant species have adapted to lower CO2 levels, most of them subtropical grasses such as sorghum, corn and millet. However, most plants – including marijuana – still feel deprived of the optimal CO2 levels they were born into.

Ziska’s research suggests plants feeling deprived will benefit from rising CO2 levels because they haven’t yet adapted to the lower levels. His own and other scientists’ work indicates the medicinal qualities of these plants may be bolstered by global warming.

Retired USDA ethno-botanist James Duke said that when plants are stressed, such as the conditions brought on by drought, they tend to exhibit more of their medicinal properties.

Duke has seen this in his “Green Farmacy Garden” in Fulton, Maryland, home to more than 300 native and non-native species of medicinal plants that have been utilized traditionally and/or researched for use in modern medicine.

“Something we learned in the garden … is that the more stress a plant gets — heat or cold or disease or just plain beating it — the more medicinal and less edible it becomes,” Duke said.

The science behind this, he said, is that stress converts proteins, carbohydrates and fats into secondary metabolites that protect the plant.

Marijuana doesn’t produce psychotropic compounds such as THC just so people can smoke it, Ziska explained. It’s a pest repellant. “Plants aren’t mobile, they can’t get up and move around, so they have to produce these chemicals to fight off pests and disease.”

More growers, less water

The marijuana market is getting crowded. As states, particularly Colorado, California and Washington, relax marijuana prohibitions, larger producers are rushing in, spilling onto public lands without regard for environmental rules in a bid to get rich quick.

In August 2011, the Center for Investigative Reporting and KQED San Francisco interviewed local law enforcement officials who said pot growers are no longer just local hippies but are increasingly armed traffickers, many of them Mexican nationals with suspected links to drug gangs across the border.

“Leniency is just bringing in more people, and it’s getting tougher and tougher,” said a veteran Northern California pot farmer we’ll call Bill who asked that The Daily Climate not use his real name. “There’s more on the market, so prices are going down while everything else is going up – fuel, the price of amendments.”

As California enters its fourth year of drought, that intensified production is taking its toll on an already taxed water supply.

A 2014 California Department of Fish and Wildlife study of one of four watersheds within the state’s so-called Emerald Triangle (prime marijuana growing counties of Mendocino, Humboldt and Trinity) estimated growers used nearly 63,000 gallons of water a day to irrigate 10,500 outdoor marijuana plants. That’s 9.5 million gallons per growing season out of one watershed. Depending on the creek monitored, that level of use amounts to between 21 and 29 percent of minimum stream flow, the amount of water necessary to preserve stream values including fish and wildlife habitat, aquatic life, water quality and aesthetic beauty.

Aerial photographs taken for the study suggest a doubling of pot production in that watershed from 2009 to 2012. The study states that fish kills, water diversions and land conversions have increased over the past few years.

Wildlife biologists in the region worry warming temperatures will increase the elevations at which pot can be grown by trespassers and thus potential threats to ecosystems.

Habitat destruction

One biologist who has been a thorn in the side of Northern California’s guerilla pot farmers has been keeping an eye both on the political climate and the mercury.

Along with colleagues at University of California, Davis, and the Integral Ecology Research Center, a nonprofit he helped launch to protect sensitive flora, fauna and ecosystems, Mourad Gabriel has been assessing pot farming’s toll on the environment. The journey began when he traced declining populations of the fisher — a small carnivorous mammal and member of the weasel family — to rat poisoning placed by growers to protect crops.

“The fisher was an environmental indicator that we had a problem,” Gabriel said. ” I draw the analogy of a festering wound where you just see the precipice and you scratch it and notice it’s much larger and is actually this neoplastic cancerous growth that’s going through our ecosystem.”

Guerilla pot farmers — those growing on public lands as opposed to their own property — divert huge amounts of water, break trails and set up camps in fragile forest ecosystems, and they use large amounts of over-the-counter and even banned pesticides completely off label both in terms of concentration and their application in riparian areas, Gabriel said.

Climate change has real potential to make the situation worse, he said.

Common practice, Gabriel said, is to tap into cold stream headwaters with ½-inch and ¼-inch irrigation line, typically running up to six miles of pipe over a 2-mile area to water scattered patches strategically placed to confound law enforcement officials.

“There is an increased threat with warming water temperatures to the salmonid populations that are essential to these ecosystem, Native American populations and commercial fisheries,” Gabriel said, not to mention aquatic invertebrates, other fisheries, aquatic mammals and avian species.

He shares other local biologists’ concerns that a warming climate will increase the geographic area hospitable to growing marijuana.

“We’ve always been curious that if nothing changes policy wise in terms of increased liberalization or enforcement, whatever side the pendulum swings, if it stays the way it is, what will occur 48 to 60 years down the line?”

Pesticides are a big part of that threat. Bill — who grows on his own land and ascribes to the axiom (in terms of law enforcement tolerance with regard to the number of plants in the ground) “99 and you’re fine” — said he looks forward to the day when farmers who grow organically will be rewarded for their stewardship.

“Why would you pump a medicinal plant with carcinogenic petroleum products?” he said.

Regulating responsibility

Dr. David Bearman, an expert in the field of medicinal marijuana, said more dispensaries are testing for molds and pesticides – including Harborside Health Center in Oakland, the largest dispensary in the U.S. – in addition to levels of cannabidiol (CBD) and tetrahydrocannabinol (THC), the compounds that get people high.

“As we refine our laws and establish [marijuana production] as a mainstream industry, it’s going to be more difficult for poor quality cannabis to get on the market,” suggested Bearman, whose résumé includes co-director of the Haight-Ashbury Drug Treatment Program.

“The problem is related to its legal status,” he said. “From 1854 until 1942, medical cannabis was legal, we didn’t have the drug cartels, and it was not a problem.”

If scientists such as Duke and Ziska are correct, global warming will increase the potency of weed grown outdoors. Coupled with Bearman’s vision, pot farmers such as Bill may be able to keep their operations modest and environmentally responsible while effectively serving both the medicinal and recreational pot markets.