Drug Intelligence Center
Domestic Cannabis Cultivation Assessment 2007
Associated Environmental Damage
Outdoor cannabis cultivation, particularly on public lands, is causing increasing environmental damage. Outdoor cannabis cultivation poses significant environmental concerns for law enforcement and other public agencies. Grow site operators often contaminate and alter watersheds; divert natural water courses; clear-cut native vegetation; poach protected wildlife; discard garbage, nonbiodegradable materials, and human waste at deserted sites; and create wildfire hazards. Moreover, the National Parks Conservation Association (NPCA) reports that while preparing land for cannabis cultivation, growers commonly clear the forest understory, which allows nonnative plants to supplant native ones, adversely affecting the eco-system. They also terrace the land--especially in mountainous areas--which results in rapid erosion. The cost of restoring land damaged by such outdoor cultivation is significant; the National Park Service estimates that for every acre of forest planted with marijuana, 10 acres are damaged, and further, the cost to repair and restore an outdoor cultivation site is approximately $11,000 per acre.
Outdoor cannabis cultivators are diverting streams and creeks for irrigation, sometimes draining natural streams and wetlands. Outdoor cannabis plots typically are irrigated with intricate watering systems. Cultivators often dam up streams and redirect the water through plastic gravity-fed irrigation tubing to supply water to individual plants (see Figure 5). Average size marijuana plots--approximately 1,000 plants--require up to 5,000 gallons of water daily. This high demand for water often strains small streams and damages downstream vegetation that depends on consistent water flow. For example, on October 4, 2006, law enforcement authorities eradicated a 1,200-plant cultivation operation in San Ramon, Contra Costa County after Park Rangers were alerted that water was no longer running in a nearby mountain stream. Cultivators had diverted the stream, building a reservoir for crop irrigation.
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