The Surprising Environmental Reason Weed Should Be Legal


Marijuana has a strange legal status. In California, it’s been medically legal for almost two decades, but growing it and selling it for recreational purposes is in a gray area of law enforcement, with federal law prohibiting it altogether and state and local laws cobbled together in a patchwork of regulation. But according to a new study, this pseudo-legalization is bad news for the environment.

The $31 billion marijuana growing business is draining local streams and allowing pesticide runoff to poison fish and wildlife, and it’s “high time” to include environmental regulations in the legalization conversation, states the report, published this week by a team of scientists from the Nature Conservancy, the California Department of Fish and Wildlife, and University of California Berkeley.

“Illegal marijuana production in California is centered in sensitive watersheds with high biodiversity,” the authors write in the report, which appeared in the journal BioScience.

CREDIT: Photograph: Scott Bauer/Bioscience
CREDIT: Photograph: Scott Bauer/Bioscience

Environmental enforcement bodies don’t have the resources to regulate rogue, unregulated pot growers under a patchwork of state and local legislation, and the federal prohibition “encourages secrecy and invisibility among producers,” the report states, further complicating enforcement. Growers are often squatting on public land, unlicensed and unregistered. The study’s authors take care to note that they are not weighing in on whether marijuana should be legalized — they are simply saying that the environmental implications need to be included in the debate.

The marijuana industry agrees.

“When you look at a lot of these problems, they are exacerbated by the fact that this [industry] is not operating within the legal structure of the state,” Taylor West, deputy director for the National Cannabis Industry Association, told ThinkProgress.


Legalizing the cannabis industry would give states “the ability to track these things and understand how they are affecting the overall environmental picture,” West said.

These problems…are exacerbated by the fact that this [industry] is not operating within the legal structure of the state

According to West, the industry is independently looking for ways to improve its environmental impact, particularly with energy issues. In Colorado, for instance, where marijuana cultivation happens almost entirely indoors using grow lamps, growers have worked with the local electricity company to improve energy efficiency of greenhouses. An organization called Greening Corporate Cannabis focuses on reducing the carbon footprint of marijuana growers, which is also a significant issue. In California, for example, indoor marijuana accounts for 9 percent of residential electricity consumption.

“It would be a better situation all around if, in places where sun growing is possible, that was an option,” West said.

But California’s crop is predominantly grown outside, which creates other issues.

Marijuana is a water-intense crop, using about twice as much water per acre of cultivation than Northern California’s more accepted vice, wine grapes. And because pot isn’t part of the agriculture infrastructure of California, growers are siphoning water directly from surface supplies such as rivers and streams, rather than irrigation tanks and reservoirs designed to withstand California’s arid summers. In addition to sourcing water in unsustainable ways, marijuana growers also avoid Clean Water Act and Endangered Species Act regulations.

“The way that we mitigate that problem is by creating a legal regulated system,” West said.

California legalized medical marijuana for some uses way back in 1996, but subsequent legislation — like the cutely named SB 420 in 2008 and a decriminalization law in 2010 — expanded access, creating the so-called “green rush” of the pot industry in the state. Roughly 5 percent of Californian adults have used medical marijuana, according to a recent study, and the state is a leading producer of pot consumed around the country. In 2013, there were an estimated 10 million outdoor plants grown in California. And that figure doesn’t even get into the indoor-grown plants, which also demand water, but also use up significant amounts of electricity.


The timing here is unfortunate. At the same time the pot business has been booming, California has been hit with a crippling drought.

Agriculture in the state — which, in addition to providing a significant amount of the country’s weed, also leads the nation in supplying dozens of fruits, nuts and vegetables — is responsible for 80 percent of California’s water consumption. In an effort to slow the diminishing water supply, farmers agreed to voluntarily curb water use.

“The very fact that we’re beginning to have a conversation about water rights is an indication of how serious the drought is,” Peter Gleick, president and co-founder of the Pacific Institute, told ThinkProgress in May. “It’s really an unusual move. I would not have guessed a year ago that we would start to have this conversation.”

So adding a new, virtually unregulated crop to the state’s water supply is a serious issue, according to the new report.

In another Northern California study, more than 80 percent of dead Pacific fishers — a rare type of weasel — recovered by researchers had been exposed to wood-rat poison, which weed growers use to ward off rats. Land use changes around black-market growing areas, such as road construction and forest clearing, additionally contribute to erosion and contamination, the report said.