Cannabis cultivation and processing, unlike cocaine or heroin processing generally do not include the use of toxic chemicals. Nevertheless, the impact of its cultivation upon forest environments in a number of countries has been no less profound. Growers of cannabis also plant their illicit crops on isolated mountain slopes, disturbing fragile forest soils. Evidence of the tragic environmental consequences of rampant cannabis cultivation is particularly apparent in Colombia and Jamaica.

Columbia, until recently, was a major producer of illicit cannabis. Most of it was grown on the fertile slopes of the Sierra Nevada de Santa Marta and the Serrania de Perija mountains in northeast Colombia. The Santa Martas, which rise abruptly from the Caribbean to 6,000 metres in just 50 kilometres, have very steeply sloping, sharp-crested ridges that radiate outward from the central part of the mountain mass. The Perija range along the Venezuelan border to the east, although lower, has a similar topography. Initially, cannabis was planted in large fields carved out of these mountain forest canyons at elevations from 1,000 - 2,000 metres. However, with the start of more effective law enforcement by Colombian authorities in the mid-1980s, growers moved to smaller plots located in much higher and more isolated mountain slopes and canyon forests to plant their illicit crops.

There is no accurate assessment of the environmental aftermath of the excessive mountain deforestation by illicit cannabis growers in northern Colombia. Descriptive accounts by leading government and private organizations including the National Police, the Geological Institute, Environmental Agencies and the Bogota press, cannot begin to depict the extensive and permanent nature of damage to these mountain environments by irresponsible narcotics organizations. Likely to be forever forfeited are the valuable forest resources and watershed, portions of national park reserves, and even indigenous lands. There are countless incidents of denuded mountain slopes and rock outcrops resulting from massive landslides and erosion. Related economic losses include the annihilation of large areas of the north coast shellfish industry, destroyed by heavy siltation from upland soil runoff, and productive lowland agriculture, a victim of increased flooding and sedimentation.

Entrepreneurial Jamaican cannabis cultivators operate with an almost total disregard for the island's fragile tropical environment. Growers clearcut and destroy hilltop and steep-sloped hillside forests, exposing marginally fertile soils to rapid runoff and erosion. Additionally, after planting and harvesting as few as two or three crops, they abandon fields in favour of new forest soils. Inspection of Jamaica's cannabis regions reveals that the most permanently damaged forest environments are those of karst topography where thin limestone soils have left bare rock incapable of sustaining secondary growth. Moreover, damage from May-June 1986 flooding in the central and western parishes, described as some of the worst in the island's history, was largely attributed to unchecked upland deforestation. Former Prime Minister Seaga, in a nationally televised address, warned that continued downstream sedimentation from upland deforestation and soil erosion will have increasingly adverse effects upon the animal and plant life of the island's mangroves and coastal reefs. (From "Illicit Narcotics Cultivation and Processing: The Ignored Environmental Drama", The United Nations International Drug Control Programme. V.93-88103 pp. 11-12.)