Associated Environmental Damage

National Drug Intelligence Center
Domestic Cannabis Cultivation Assessment 2007
February 2007

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.

Dangerous Poisons From Mexico Polluting California National Forests

According to NFS and California Bureau of Narcotics Enforcement Campaign Against Marijuana Planting (CAMP), law enforcement officials are increasingly encountering dumpsites of highly toxic insecticides, chemical repellants, and poisons (see Figure 4) that are produced in Mexico, purchased by Mexican criminal groups, and transported into the country for use at their cannabis grow sites. Although similar chemicals could be purchased in the United States, many Mexican DTOs are simply using Mexican chemicals rather than purchasing bulk quantities locally, which could alert law enforcement to their cultivation operations. Cultivators apply insecticides directly to plants to protect them from insect damage. Chemical repellants and poisons are applied at the base of the cannabis plants and around the perimeter of the grow site to ward off or kill rats, deer, and other animals that could cause crop damage. These toxic chemicals enter and contaminate ground water, pollute watersheds, kill fish and other wildlife, and eventually enter residential water supplies.

Source: U.S. Department of Agriculture Forest Service; Environmental Protection Agency.

Figure 4. Toxic insecticide bottle found at a cannabis cultivation operation in California, 2006.

Photo showing a toxic insecticide bottle found at a cannabis cultivation operation in California, 2006.

U.S. Department of Agriculture Forest Service

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.

Figure 5. Reservoir used in a cannabis cultivation operation in the Shasta-Trinity National Forest in 2006.

Photo showing a reservoir used in a cannabis cultivation operation in the Shasta-Trinity National Forest in 2006.

U.S. Department of Agriculture Forest Service

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