Marijuana Legalization Leads to Fewer Illegal Grow Sites, Study Finds

A new scientific study finds that the number of illegal marijuana grow sites in National Forests decreases after adult use marijuana is legalized.

A first-of-its-kind study reveals a new benefit of marijuana legalization. According to researchers with the United States Department of Agriculture’s Forest Service, the number of illegal marijuana crops grown in federally-protected parks drops once a state legalizes marijuana.

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

USDA Forest Researchers first analyzed U.S. Department of Justice data on the number of illegal grow sites between 2004 and 2016 alongside changes in state marijuana laws.

They then used their dataset to run simulations, comparing how different marijuana policies may influence the presence of illegal grows. They also used simulations to test the effects of marijuana tax laws and increased police enforcement on illegal grow sites.

Published recently in the journal Ecological Economics, the study found that “policies legalizing recreational cannabis production and consumption are associated with significantly lower numbers of reported illegal grows on national forests.”

Decriminalization alone did not have the same curbing effect on illegal grows, which is logical since it does not allow for a system of legal cultivation or distribution. According to the simulations, a 20 percent increase in law enforcement manpower would spur only a 2.5 percent decrease in reported illegal grows.

Illegal cultivation would also decrease with a 6 to 13 percent reduction in taxes on legal marijuana sales. However, the “availability of legal cannabis does not encourage illegal cultivation unless the after-tax price for legal cannabis is substantially elevated relative to the illegal product,” the researchers wrote.

The researchers say the predictive models indicate that illegal marijuana grow sites would decline 35 to 51 percent across the United States if all states with medical marijuana more broadly legalized recreational use. Medical marijuana legalization alone appears to not have any impact on illegal grow operations.

“Arguably, 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,” the researchers concluded.

Eleven states have legalized recreational marijuana so far. Illinois is the most recent to do so.

The study, “Cannabis legalization by states reduces illegal growing on US national forests,” is available to access through Science Direct.

Impact of Illegal Marijuana Grows

Environmentalists are particularly opposed to illegal marijuana growing because the activity often involves the use of harmful chemical fertilizers and pesticides that adversely affect surrounding plant life.

Additionally, there are concerns over the uncontrolled use of clear-cutting and terracing of national park land, leading to a loss of trees. Illegal grow site workers may also partake in the poaching of the local wildlife.

The study’s findings suggest that marijuana legalization can play a significant role in protecting National Forests from the lasting environmental damage of illegal grows. A separate study recently found that marijuana cultivation on federal lands in the Pacific Northwest dropped after marijuana was made legal.

Those who wish to stamp out the illegal marijuana market will find it unfortunate that it still represents at least 30 percent of cannabis sales.

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