By 2013, illegal cannabis grows were such a destructive environmental force in California that state water regulators decided it was time to go beyond their complaint-driven, piecemeal approach at enforcement.
That required knowing how much cannabis there was statewide, and where.
Nearly a decade later, the answer still eludes California.
So the Los Angeles Times embarked on its own effort to map illegally grown cannabis, one that depended on a view from space.
Cannabis operations are easy to spot in satellite imagery. Plastic-covered hoop houses and plots of individual dark-green plants are distinctive and hard to miss, even more so in clear-cut tracts of forest or vast expanses of desert.
The Times obtained 2021 satellite imagery from a mix of public and private sources to canvass nearly 3,000 square miles of land in parts of six counties: Siskiyou, Trinity, Mendocino, Shasta, Butte and San Bernardino.
The analysis counted outdoor cultivation spots and measured the square footage of greenhouses. It avoided areas with other active agriculture that could be mistaken for cannabis, and looked for telltale signs of weed, such as outdoor swimming pools to hold water and outdoor plots adjacent to hoop houses.
To estimate greenhouse crops, The Times used industry-supplied yield formulas. Not all greenhouses were filled and some crops were lost to wildfire or police raids, so The Times followed another industry practice and reduced raw crop estimates by 30%.
Measured that way, the survey area contained 25 million square feet of illicit greenhouses with ample capacity to grow 2.6 million pounds of weed — enough to supply the entire legal California market.
The illegality of these grows was determined using licensing maps obtained from the state Department of Cannabis Control, county permit databases, hemp registrations and tax assessor parcel records. On Native American reservations, where unique ordinances sometimes permit commercial cultivation, The Times also used ownership maps obtained from the Department of Interior’s Bureau of Indian Affairs.