Legalizing Marijuana Leads To Fewer Illegal Grow Sites In National Forests, Study Finds

Here’s the story from Marijuana Moment and there’s more at the link too.


In news that Smokey Bear, iconic protector of all forests, would be happy to hear, research shows that reports of illegal marijuana grow operations on federally protected lands fell after states began legalizing it for adult use.

“Arguably,” the study authors write, “our models hint that outright, national recreational cannabis legalization would be one means by which illegal growing on national forests could be made to disappear.”

“[W]e find that recreational cannabis legalization is associated with decreased reports of illegal grow operations on national forests.”

The research, which was published in the journal Ecological Economics earlier this month, is thought to be the first of its kind to analyze the effects of legalization policies on illegal outdoor grows in national forests throughout the United States. A separate recent study found that cannabis cultivation on federal lands specifically in the Pacific Northwest declined after legalization.

Researchers with the United States Department of Agriculture’s Forest Service used existing data on the number of illegal grow sites reported between 2004 and 2016 in 111 national forests. In addition to incorporating other variables into their analysis (including state marijuana policies, retail price for consumers, risk of exposure and others), they also came up with six simulated scenarios with policy changes to create random effects models of the number of reported grows.

For example, in one scenario, the study’s authors estimated how many illegal grow sites would exist if current laws legalizing both recreational and medical marijuana were revoked. In another simulation, wholesale and retail sales taxes on legal marijuana were eliminated in states that had already approved the sale and consumption of cannabis in 2016.

According to the study’s findings, “policies legalizing recreational cannabis production and consumption are associated with significantly lower numbers of reported illegal grows on national forests.”

The study’s predictive models showed that eliminating current state laws legalizing access to marijuana would result in “double-digit percentage increases in reported grows on national forests, while further expansion of the set of states with such laws passed by statewide referenda in 2016 (but only instituting applicable laws in 2017 or later, post-dating our dataset) would be expected to reduce growing on national forests by a fifth or more.”

If all 23 states that had approved medical marijuana by 2016 moved to more broadly legalize for adult use, the study continues, illegal cultivation sites in national forests would decline anywhere from 35 percent to 51 percent. However, it concluded that legalization of medical cannabis across the U.S. alone would not affect grow operations in national forests.

Mere decriminalization of possession was also found to have no significant effect on the number of illegal farms, though models did show that harsher penalties for illegal production and possession of marijuana, as well as stricter regulations on CBD oil and similar products, did. Meanwhile, an increase in law enforcement presence only made a slight difference (a 2.5 percent decrease in reported illegal grows) if local agencies increased their manpower by 20 percent.

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The Report

The effects of recreational cannabis legalization on forest management and conservation efforts in U.S. national forests in the Pacific Northwest


•Cannabis production in Pacific Northwest national forests is of ecological concern.
•Socio-economic factors significantly affect cannabis production in national forests.
•Cannabis legalization negatively impacts illicit cultivation in Oregonian forests.
•Cannabis legalization is insignificant in Washington.
•Stagnant and declining resources for US Forest Service are environmentally troubling.


Cannabis cultivation in US national forests has been identified as a growing environmental issue. Rational choice theory often considers law enforcement efforts as pushing this illegal activity into remote areas, including public lands, through the process of crime displacement. As such, the legalization of recreational cannabis has been prescribed as a possible solution to this environmental issue. The recent liberalization of marijuana policies across numerous states introduces the opportunity to analyze these claims. Here, utilizing regression analyses, we investigate the effects of recreational cannabis legalization and a host of relevant socio-economic and law enforcement factors in Washington and Oregon on illicit marijuana cultivation in Pacific Northwest national forests. To further investigate the regression results, structured questions were sent to a key informant of the United States Forest Service Law Enforcement and Investigations division who responded on behalf of the institution. Results demonstrate law enforcement and economic variables as significant in determining illicit cannabis cultivation in Pacific Northwest national forests, confirming the relevance of a rational choice framework. Recreational cannabis legalization is found to significantly contribute to a reduction in illicit cultivation sites in Oregonian national forests, while remaining insignificant in Washington, likely due to policy differences that are discussed.

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