Clandestine cannabis farms in California and Oregon infringe on the habitats of several threatened and endangered species, potentially exposing vulnerable animals to toxic pesticides, new research has revealed. According to the study authors, harmful rodenticides used by illegal weed growers have the potential to accumulate in local food chains and destabilize fragile ecosystems.
While cannabis has been legalized in both California and Oregon, unlicensed growers continue to produce the plant illegally, often selecting hidden spots in highly forested regions for their cultivation sites. Publishing their work in the journal PLOS ONE, the researchers show how these hidden away sites are affecting local forest predators, such as the endangered Pacific fisher and threatened Humboldt marten and northern spotted owl.
The team collaborated with law enforcement agencies to obtain data relating to the location of 1,469 illegal weed farms that had been busted between 2007 and 2014. Based on this information, they were able to identify certain landscape characteristics favored by these illegal growers and map the likely distribution of unlicensed grow sites in the forested regions of California and southern Oregon. For example, they found that illegal cannabis growers tended to pick spots with low to mid-elevation and with moderate slopes, as such locations allow for gravity-fed irrigation while also benefiting from a reduced human presence compared to low-elevation sites.
Equipped with this insight, the authors were able to identify a 21,607-square-kilometer (8,343 square miles) region of forest with a high likelihood of illegal cannabis cultivation. To verify this, the team physically surveyed a number of streams within this region that they had identified as prime spots for illegal cannabis operations and discovered 16 previously undetected farms within a relatively small area.
They then superimposed their cannabis farm distribution map over the geographical habitats of the endangered Pacific fisher, the threatened