California state law now allows marijuana with a prescription, and new legislation would make it legal for all adults, raising $1.4 billion in new taxes. But law enforcement officials say one thing hasn't changed: pot farms still illegally use - and often scar - California's forests.

As part of a massive sweep, more than 300 agents from 17 agencies have spent the past 10 days hiking through and flying over Fresno County's secluded forests to destroy tens of thousands of plants worth hundreds of millions of dollars.

Authorities arrested dozens of people and seized dozens of weapons, said Fresno County sheriff's deputy Chris Curtice.

"This is about growing illegal marijuana on public lands and state and federal parks," said Curtice. "This is not about legalization of marijuana, it's about growing illegal marijuana on public lands, the damage it does to the environment and the danger it poses to the public because of the people involved."