According to the Campaign Against Marijuana Planting, a multiagency task force managed by the state’s Bureau of Narcotic Enforcement, this year is already one for the record books. In more than 425 raids since late June, some 3.4 million plants have been seized, up from 2.9 million all of last year. And, officials note, they still have roughly a month and a half before the campaign expires with the end of harvest season.

Raids occur daily, from southern counties like Riverside, where some 27,000 plants were found on July 2, to northern ones like Lake and Shasta, in each of which more than 400,000 plants have been destroyed by the authorities this year. (Mature plants are usually incinerated, younger ones simply uprooted.)

Image A spartan campsite built by growers. Credit... Santa Barbara County Sheriff’s Department

About 2.7 million plants, nearly 80 percent of the seized crop, have been found on federal, state or other public lands. Officials attribute the plants’ prevalence there to the vast area investigators are expected to cover.

“It’s rugged terrain, very difficult to get to and very difficult to see,” said John Heil, a spokesman for the United States Forest Service, which in California has jurisdiction over 20.6 million acres, home to nearly 60 percent of this year’s seizures.

Mr. Heil said drug operators could be blamed for a handful of wildfires each year in California, which is already dealing with a prolonged drought and budget-stretched firefighting resources. Environmental damage of a different kind can also be severe, with pesticides seeping into soil and streams, and trash and human waste left behind.

Lieutenant LeGault said he was impressed by how far marijuana growers would go  deeper into forests, higher in the mountains  in an effort to avoid detection. “They call it a wilderness because it is,” he said. “Not even the billy goats go there.”