Assessing Cannabis pollen representation in the Rif Mountains via modern pollen analysis

Modern pollen data are indispensable reference tools for reconstructing paleoenvironments and cultural landscapes. However, the importance of understanding the pollen released from Cannabis L. cultivation remains unexplored. Specifically, the role of Cannabis L. cultivation in the past and the current agricultural landscape has not been investigated, hindering efforts to understand its historical context in Morocco. This study assesses the representation of Cannabis L. pollen across land uses and variables. We conducted a pollen analysis on 40 moss samples collected from various altitudinal ranges across the Rif Mountains, a region known for its diverse agroforestry landscape and the cultivation of Cannabis L. The Cannabis pollen representation is highly variable across the variables (distance, land use, tree cover). The samples collected closest to the hemp fields registered Cannabis pollen levels reaching up to 25%, while a decrease (< 10%) was observed in samples collected 200 m away. The findings indicate that increased distance and tree cover harm the quantities of Cannabis pollen, whereas land use exhibited a positive correlation with Cannabis pollen levels. Moreover, other variables such as wind direction, field size, and geographical location of the field and sampling sites may impact the pollen amounts. We concluded that the quantity of Cannabis pollen in the region displays significant variation across various variables, indicating its potential for reconstructing the historical context of hemp in the Rif Mountains and identification of ancient cultivation trends. However, further research is needed to explore the relationship between Cannabis pollen production/dispersal patterns and other factors in more depth.