Cannabis Crop Expansion Threatens Wildlife Habitats

November 01, 2017

Planting cannabis for commercial production in remote locations creates forest fragmentation, stream modification, soil erosion, and landslides. Without land-use policies to limit its environmental footprint, the impacts of cannabis farming could get worse, according to a new study published in Frontiers in Ecology and the Environment.

“To mitigate the anticipated environmental impacts, now is the time for policy makers and land-use planners to set regulations to manage the spatial pattern of cannabis expansion, before crop production becomes established,” said co-author Van Butsic, a Cooperative Extension specialist in the Department of Environmental Science, Policy, and Management (ESPM).

Cannabis, as either a medicinal or a recreational drug, is now legal in more than 30 U.S. states and several other countries. In California, where medicinal marijuana has been legal since 1996, voters approved the sale and possession of one ounce of marijuana per person for recreational use in November of last year. As a result, cannabis production is ramping up.

Earlier studies have shown that cannabis production causes environmental damage, including the rodenticide poisoning of forest mammals and the dewatering of streams due to improper irrigation.

In this study, Butsic, ESPM assistant professor Ian Wang, and Jacob Brenner of Ithaca College compared the effects of cannabis cultivation in Humboldt County from 2000 to 2013 with those of timber harvests during the same period. Based on the size, shape, and placement of the cannabis grows within 62 randomly selected watersheds, they quantified the grows’ impacts relative to those of timber harvests.

“We found that although timber has greater landscape impacts overall, cannabis causes far greater changes in key metrics on a per-unit-area basis,” Butsic said.

The cannabis grows resulted in 1.5 times more forest loss and 2.5 times greater fragmentation of the landscape, breaking up large, contiguous forests into smaller patches and reducing wildlife habitats.

Current California law caps the size of outdoor cannabis production at one acre per parcel, to prohibit the development of industrial-scale cannabis operations outdoors. An unintended consequence of this law may be smaller, dispersed cannabis grows that edge out wildlife.

— Adapted from an article by Pamela Kan-Rice