Collateral Impact: Illegal marijuana is spreading on public lands—here’s what’s concerning officials

Deep in Colorado’s national forests, shadowy teams of people are clearcutting underbrush, trenching hillsides for cultivation, diverting and damming streams to create reservoirs and using chemicals that are killing fish and wildlife. They leave behind animal carcasses, garbage and human waste, polluting mountain streams.

And the destruction is spreading.

In a state where growing and selling cannabis have been legal for years, illegal marijuana grow operations in national forests have been on the rise for at least the last three years, officials say.