The summer is prime time for marijuana harvest, said KGPE correspondent Amy Allen, and the Sheriff's Department, working with the Forest Service, the California Department of Justice, and the Bureau of Narcotics Enforcement and have cleared out 40,000 pot plants in remote areas in just three days.
A single plant may produce $4,000 worth of marijuana.
A report by the National Drug Intelligence Center says California's Central Valley is one of the most significant cultivation areas for cannabis in the country.
In 2008 authorities eradicated more than 5.3 million cannabis plants (both indoor- and outdoor-grown) in the state, according to the Drug Enforcement Administration (DEA), and about one-quarter of those were in the Central Valley.
Data also shows that outdoor cultivation has been on the rise over the past five years in Fresno, Kern, Shasta and Tulare Counties.
During a raid near Balch Camp, Calif., Lt. Bob Miller of the Fresco County Sheriff's Department told CBS affiliate KGPE that illegal growers cut down and cleared out trees and hauled in fertilizers, drip lines and other equipment. "Extremely, extremely sophisticated operations," he said.
The eradication of the illegal gardens is not just to keep drugs off the streets but also to prevent environmental damage: Highly-toxic chemicals from the growing sites - from pesticides and chemical repellents to rat poison - pollute watersheds, harming fish and wildlife and eventually getting into the water supply.
The Fresno Bee reports that at one encampment in the foothills of the eastern part of Fresno County, approximately 10,000 plants were growing in a one-third acre patch. A shelter with kitchen and canned supplies were also found.
Forest Service volunteers will help clear out trash from the encampments.
Also this week, authorities removed about 3,500 marijuana plants found growing in park land in the Santa Monica Mountains.
The National Park Service said Wednesday that trash, pipes, camping equipment, fertilizer and pesticides were also removed Tuesday from three plantations - two located in Malibu Creek State Park and one in the Zuma-Trancas Canyon area.
Authorities said it costs up to $12,000 to clean up an acre of cultivated pot, taking away money that could be spent on other public services.