TNC Marijuana Study: High Time for Conservation

Mike Sweeney, Executive Director of the California Chapter of The Nature Conservancy (TNC), believes that some of the most important work they do is provide the science necessary to drive change across the state and nation.  You can access TNC’s recently published study via the link below.

High Time to Clean Up Marijuana’s Environmental Mess
Marijuana. Pot. Weed. Cannabis. Mary Jane.

So many ways to talk about it, but no one knows what pot really means for California.

California grows 60 to 70 percent of all the pot in the U.S. and the $16 billion harvest often comes from illegal grow farms in Northern California where forests are cleared, rivers are sucked dry or tainted with chemicals, and animals are poisoned. Take the Pacific fisher, a member of the weasel family that looks like a bear cub, which dies when rodenticide liquefies its insides (bottom right photo). Pot growers use pounds of this stuff, which has killed animals as big as a black bear.

Marijuana is a thirsty crop – it uses twice as much water as wine grapes – and most of this water is being illegally diverted from streams during the worst drought in recorded history. Meanwhile, there is not enough funding for restoration, regulation or enforcement of environmental laws, and growers often try to protect their crops with military-grade weapons and booby traps. This makes it difficult for scientists to understand the full scope of the problem and what needs to be done to fix it.

With legalization on the horizon, and demand for weed growing, we need to get a handle on this before the “green rush” leaves California high and dry.

Today we released a study in the journal BioScience that addresses this issue: High Time for Conservation: Adding the Environment to the Debate on Marijuana Liberalization.

In the coming weeks, you’ll hear more as we promote this study. Read more on

Mike Sweeney
Executive Director, California Chapter
The Nature Conservancy

Photos, from left: A marijuana grow site discovered on public lands; Trash from marijuana cultivation pollutes land and water; Sheriff Mike Downey with a Pacific fisher that died from rodenticide. © Department of Fish and Wildlife and Humboldt Sheriff's Department.

Photos, from left: A marijuana grow site discovered on public lands; Trash from marijuana cultivation pollutes land and water; Sheriff Mike Downey with a Pacific fisher that died from rodenticide.
© Department of Fish and Wildlife and Humboldt Sheriff’s Department.


CDFW Scientists Publish Groundbreaking Work on Marijuana’s Effect on the Environment

Environmental scientists with the California Department of Fish and Wildlife (CDFW) recently published a first-of-its-kind study that clearly shows that water used for growing marijuana has a devastating effect on fish in the state.

The study showed that during drought conditions, water demand for marijuana cultivation exceeded stream flow in three of four study watersheds. The resulting paper, entitled “Impacts of Surface Water Diversions for Marijuana Cultivation on Aquatic Habitat in Four Northwestern California Watersheds,” concludes that diminished stream flow from this water-intensive activity is likely to have lethal to sub-lethal effects on state and federally listed salmon and steelhead trout and will cause further decline of sensitive amphibian species.

The study was published online in the scientific journal PLOS One and can be found   here.

By using online tools to count marijuana plants and measure greenhouses, and conducting inspections of marijuana cultivation sites with state wildlife officers and local law enforcement, CDFW scientists quantified plant numbers and water use. Utilizing stream flow data provided by staff at the National Oceanic and Atmospheric Administration (NOAA), CDFW determined water demand for cultivation could use more than 100 percent of stream flow during the summer dry season in three of four study watersheds. Stream flow monitoring conducted by CDFW in the summer of 2014 appeared to verify these results.

“All the streams we monitored in watersheds with large scale marijuana cultivation went dry,” said CDFW Senior Environmental Scientist Scott Bauer, lead author of the research paper. “The only stream we monitored that didn’t go dry contained no observed marijuana cultivation.”

Additional negative impacts of trespass grows include wildlife poisoning, human waste and trash, and soil and water pollution.

Trespass grows also contribute human waste and trash, pollute soil and water, and poison wildlife.

CDFW’s Law Enforcement Division works closely with dozens of other state and federal agencies to eradicate illegal marijuana grows on public, tribal and private lands as well as protect the state’s natural resources.

“This research paper demonstrates the importance of greater regulatory efforts by state agencies to prevent the extinction of imperiled fisheries resources,” said CDFW Assistant Chief Brian Naslund. “CDFW’s new Watershed Enforcement Team (WET) was created with just that in mind.”

The WET program works with agency partners to protect public trust resources from the negative effects of marijuana cultivation, which include both excessive water use and pollution.

CDFW will continue to monitor the effects of water diversion for marijuana cultivation on stream flow through the summer of 2015.

Marijuana cultivation is legal in California if growers have the proper CDFW lake and streambed alteration permits. Responsible growers help conserve the state’s natural resources and are less likely to be subject to enforcement action.