Patterns and Correlates of Unlicensed Cannabis Cultivation in California(USA) Following Adult-Use Legalization

Since the legalization of cannabis in California (USA), unlicensed cultivation has unevenly persisted. Spatial patterns are likely associated with a combination of physical and socio-political factors, though their relative importance remains unexplored. This study examines interannual growth and decline in unlicensed cultivation, the spatial patterns of relocation, redistribution, and clustering, and the relationship between unlicensed cultivation and potential environmental impacts. It uses multi-year spatial data (from 2018–2024) and Generalized Additive Models (GAMs) to conduct landscape-scale analyses of geographic trends, changes in cultivation density, and associations with physical and socio-political characteristics. We found that physical characteristics such as topography, building density, and remoteness were associated with changes in cultivation density, though the direction and magnitude of effects varied across periods. Socio-political factors, including enforcement intensity, fines, bans, and the presence of licensed farms, exhibited complex and sometimes opposing temporal patterns. Licensed farms were the single largest and most consistent predictor of reduced unlicensed cultivation (estimates ranged from  -207.79 to -660.06 m2 per km2), suggesting that active participation in permitting regimes fosters stability, norm formation, and deterrence. In contrast, bans and enforcement alone often redistributed cultivation, producing “whack-a-mole” dynamics that increased volatility and, in some cases, environmental exposure. Environmental sensitivity emerged as a significant factor in later periods, with regulated counties showing reductions in cultivation in vulnerable areas, highlighting the potential for permitting systems to mitigate ecological impacts. These findings emphasize the importance of participatory, stable, and well-implemented regulatory frameworks for managing unlicensed cultivation and provide broader insights for formalizing informal or illicit resource use in varied socio-ecological contexts.