Experts warn illegal marijuana grow sites are becoming a threat to the environment.
Dr. Mourad Gabriel is a field agent for the Integral Ecology Research Center. He goes with a team into marijuana cultivation sites in California forests to study the environmental impacts.
Besides the mounds of trash, Gabriel also finds piles of human waste and dangerous pesticides -- some that are illegal in the United States.
"Just even walking in these sites can even put you at risk," said Gabriel. "One-sixteenth of a teaspoon is enough to kill a male adult and we find gallons of it."
Often times, Gabriel says the human waste and pesticides are near waterways.
"We all live downstream," said Gabriel. "Many of these lands that are being cultivated on -- there's municipalities below them. So, therefore, the individuals who use spring water, the individuals who are hiking and backpacking and maybe pulling water out for that hike, the cattle ranchers who are using the water for their livestock, the individuals who are hunting or fishing who are consuming game species that utilize these lands. We have the data that's demonstrating that these are potential groups at risk."
The problem isn't just plaguing forests in California, according to Gabriel. In Arizona, federal investigators have discovered illegal grow operations in the forest.
Some say legalizing marijuana would help because it would add regulations to the industry. However, Gabriel says more data needs to be collected on that.
"With each step that's gone forward in policy the enforcement has actually dissipated," said Gabriel.