Cannabis in Forested Landscapes

There are many unknowns when making environmental policies for cannabis, including how cannabis farms relate to forest clearing. In Northern California, timber is one of the dominant industries alongside cannabis and other agricultural crops. Our researchers conducted one of the first studies to document how the cannabis industry impacts forest relative to the timber industry. We found that the timber and cannabis industry are associated with different effects on forest cover. Timber harvest affects large stands of forest and is associated with more than 10 times more forest clearing than cannabis production. Cannabis on the other hand is associated with smaller clearings, but greater losses of core forest area and increased forest edge.  When we analyzed the per unit area effects of these different industries, we found that both had impacts on a number of measures of forest intactness.

The differences in these industries with respect to forest clearing could be in part to their differing legal status. As cannabis remains federally illegal, grows are often placed in more remote landscapes, away from roads. These landscapes are often in core forest areas with relatively little human disturbance. Another difference is that when trees are cleared for timber, they are  replanted. Cannabis is a much younger industry than timber, and so it remains unclear whether or not trees would be replanted where cannabis is grown, if cannabis farming ceases.

In a more recent study within our Center (Butsic et al. 2018), we found that between 2012 and 2016 in two counties in Northern California, cannabis farms increased in number by 58%. We also found that 88% of these new sites were developed on previously natural landscapes, with forest being the most common landscape type. These results indicate that cannabis expansion is likely still leading to forest clearing. The future impacts of cannabis on forests depend on many factors, including how grower networks respond to legalization. Our researchers Hekia Bodwitch and Michael Polson are continuing to interview cannabis growers throughout California to have their voices heard throughout the policy making process. With respect to deforestation policies, Bodwitch and Polson have already found that minimum size limitations on cannabis farms may force cannabis farmers to operate more, smaller farms, potentially accelerating the fragmentation of forested landscapes*.  This example serves as a reminder to proceed with care, do more research, and include all stakeholders when creating environmental policies for cannabis.

*Click here to read more about their project.