How we mapped illegal cannabis farms in California – By 2013, illegal cannabis grows were such a destructive environmental force in California that state water regulators decided it 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.