Illegal marijuana growers in California illegally clear the trees from the land then damn up the natural streams on these public owned tracts of land. These pristine forests and streams have been growing and flowing conceivably thousands of years. The illegal growers then draw down the water from the damned up streams to cultivate their illegal plants. This destroys the environment, the plants and wildlife that thrive in these areas.
To also protect their illegal crops the illegal growers put out rat poison to keep wild animals from eating their illegal crops which causes the wildlife to die a slow and painful, horrific death. These poisons also creep into the local streams and ecosystem causing environmental problems in the future that have yet to even be calculated since it has only been a few years that hundreds of illegal marijuana growers have appeared and taken over certain parts of the California hills.
SUPPLEMENTAL SOURCE: CALIFORNIA DEPARTMENT OF FISH AND GAME 7/23/12