In 2025, researchers at the UC Berkeley Cannabis Research Center released Mapping & Assessing Unlicensed Cannabis Cultivation, one of the most comprehensive analyses to date of trends in unlicensed cannabis cultivation across California. Using satellite imagery, field verification, and county-level case studies, including Nevada County, the researchers evaluated how local policies, enforcement approaches, and licensing programs influenced the prevalence of unlicensed cultivation. One of the study’s most significant findings was that the presence of licensed cannabis farms was the strongest and most consistent predictor of reductions in unlicensed cultivation. Contrary to the common assumption that enforcement alone is the primary solution, the study found that areas with active licensed cultivation generally experienced greater declines in unlicensed cultivation than areas relying primarily on bans and eradication efforts. 

The researchers concluded that maintaining a robust network of licensed farms may be one of the most effective strategies for reducing the environmental impacts associated with cannabis cultivation. Licensed operations are subject to environmental regulations, water-use requirements, inspections, and compliance monitoring that do not exist for unlicensed sites. The study found that permit programs help create a culture of compliance and increase regulatory visibility across the landscape, making it more difficult for unlicensed operations to persist. Researchers also observed that counties with active permitting programs often experienced greater reductions in cultivation within environmentally sensitive areas, suggesting that regulated cultivation can contribute to improved watershed protection and environmental outcomes over time. 

The study also found that local cultivation bans and enforcement actions produced mixed results. In many cases, cultivation did not disappear; instead, it shifted to more remote locations, a phenomenon researchers described as a “whack-a-mole” effect. The report suggests that long-term reductions in environmental impacts are more likely to be achieved through a combination of reasonable regulation, effective permitting programs, and targeted enforcement rather than through enforcement alone. 

These findings reinforce the importance of bringing cultivation into a regulated framework where water use, land management, and environmental protections can be monitored and enforced, ultimately benefiting both watersheds and local communities. 

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