The quasi-legal status of marijuana cultivation in California has left this industry (that supplies approximately 60-70% of marijuana consumed in the United States) largely unregulated and responsible for a cascade of severe environmental impacts. Marijuana crops on California’s North Coast are primarily grown outside, on both public and private forestland that is critical wildlife habitat and vital for water quality.

While the footprint of marijuana grow sites may be relatively small, associated environmental impacts are disproportionately large. To supply both the medicinal and black markets, forest patches are cleared of trees and new roads are cut to access grow sites. These activities create erosion and sediment-clogged streams. Further, marijuana production consumes resources at a high rate – draining streams because the crop uses at least twice as much water as vineyards, leaking fertilizer into waterways, and poisoning wildlife through the application of rat poisons. Imperiled species such as salmon, spotted owls, and Pacific fisher are paying the consequences for woods-grown weed.

A new research paper in Bioscience by Jennifer Carah and colleagues (High Time for Conservation: Adding the Environment to the Debate on Marijuana Liberalization) calls for a direct policy response to reduce, regulate, and mitigate environmental harm from marijuana cultivation in California, making an important, timely, and science-based contribution to inform the political debate.