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Is the grass greener on the other side?

Drug legalization could both help and hurt the environment


By Hillary Rosner

Social transformations that once took generations to cement now seem to cover the globe in a matter of years. The legalization of marijuana is a case in point. Uruguay, the Netherlands, Morocco, and a growing list of countries are decriminalizing the forbidden weed. And individual US states are following suit, trailing a wave of public opinion. In a 2016 Pew survey, 57 percent of US adults said marijuana use should be legalized, while 37 percent said it should be a crime. That’s nearly the reverse of public opinion on legalizing pot a decade ago.

The reasons for the about-face vary from a desire to curb the violence inflicted by drug cartels, to concerns over vastly uneven criminal prosecution, to access for medicinal uses. Rarely, however, does the list include abating the environmental damage the illegal drug trade wreaks.

Growing 1 kilo of pot generates roughly the carbon emissions of burning 516 gallons of gasoline

But perhaps it should. The ecological impacts of the black-market drug trade are crushing. In Colombia, for example, the cocaine trade was responsible for more than half of all forest loss in the 1990s. (1) According to one study, the spread of coca crops to feed global demand for cocaine “threatens the last repositories of imperiled forest species more efficiently than most other causes of forest fragmentation.” And across Central America—particularly in the Caribbean lowland forests of Nicaragua, Honduras, and Guatemala, an area teeming with remarkable plants and animals—drug trafficking is speeding the destruction, lighting a match to the tinderbox built from poverty, illegal logging, industrial agriculture, and weak enforcement, according to research published in 2014. (2)

As cartels push drug crops into increasingly remote areas to avoid law enforcement, the devastation spreads. Herbicides, pesticides, and fertilizers threaten fragile ecosystems. Exact numbers are hard to come by, but one study reported that in 2005, coca growers in Colombia used 81,000 tons and 83,000 barrels of fertilizers and toxic weed and pest killers. (3)

Drug traffickers often launder money and seek to “legitimize” their presence in an area through agriculture—converting even more forests to pasture or oil palm plantations. (2) And the violence that follows cartels into remote areas makes wildlife monitoring and other scientific research more and more perilous.

Even enforcement efforts can deal a blow. In a 2005 trial program, the Colombian government sprayed a deadly herbicide to destroy vast coca crops illegally planted across 13,000 hectares of a national park and surrounding lands. Instead of protecting the park, the government was bombarding it with toxic chemicals. (4)

In the US, illegal pot farms have set up shop on public lands with devastating environmental consequences. Some are sucking entire ecosystems dry. Marijuana plants use almost twice as much water per square kilometer as wine grapes, northern California’s other major irrigated crop. (5) One study found that water demand for pot cultivation could slash the water available in streams by nearly one-fourth, killing endangered salmon and steelhead trout as well as amphibians. (6)

Terrestrial wildlife takes a hit, too. Several years ago, in forests in northern California and in the southern Sierra Nevada range, scientists began finding a lot of dead Pacific fishers (a forest-dwelling mammal similar to the weasel and a candidate for listing under the Endangered Species Act). Testing revealed that nearly 80 percent of the dead animals, including adults and their kits, contained lethal rodenticides that pot growers use to keep rats from eating their plants and gnawing through their irrigation lines. (7)

All this bad news raises the question: Could legalization offer even a modicum of relief?

Legalizing marijuana in all 50 US states might put drug cartels out of work—solving the public lands problem and even reducing the use of poisons that kill wildlife. But even legal marijuana farming isn’t benign. New research shows that indoor pot production—legal and illegal—is a “previously unrecognized source of energy consumption,” responsible for as much as 1 percent of total US electricity use. Growing 1 kilo of pot generates roughly the same amount of carbon emissions as burning 516 gallons of gasoline. And out of 20 industries, from textiles to tobacco to plastics, marijuana had the highest energy intensity—more than double any other one except paper. (8) Already, energy demand for indoor pot operations in Washington state—where the drug has been legal since 2012—is projected to double by 2035, according to a report from the Northwest Power and Conservation Council.

Still, legalization done right might offer an antidote. Gina Warren, a law professor at Texas A&M, has looked at drug legalization trends in terms of energy regulation, and she believes that new state licensing regulations offer a chance to limit the greenhouse gas emissions of indoor grow operations. Warren recommends that states and cities should consider energy usage and emissions when granting licenses—and even require pot growers to use only renewable energy. Even without such regulation, simply bringing illicit growers out of the shadows could ease some of the environmental externalities. For example, instead of stealing electricity or running generators, growers would plug into the grid. They could then take part in utility energy-efficiency programs and have a financial incentive to use cleaner, off-peak power. (9)

It’s too soon to know what the impact of state-by-state or even countrywide legalization will be—partly because there’s virtually no funding to study it. That seems an opportunity lost. Drug policy is flipping right before our eyes. If we paid more attention, perhaps we could make some drugs, particularly the world’s most sought-after weed, a little greener.

1. Álvarez MD. Illicit crops and bird conservation priorities in Colombia. Conservation Biology. 2002.
2. McSweeney K et al. Drug policy as conservation policy: Narco-deforestation. Science. 2014.
3. United Nations Office on Drugs and Crime. World Drug Report 2015.
4. Dávalos LM and AC Bejarano. Conservation in conflict: Illegal drugs versus habitat in the Americas. In: State of the Wild 2008–2009: A global portrait of wildlife, wildlands, and oceans 2. Island Press. 2008.
5. Carah JK et al. High time for conservation: Adding the environment to the debate on marijuana liberalization. BioScience 2015.
6. Bauer S et al. Impacts of surface water diversions for marijuana cultivation on aquatic habitat in four northwestern California watersheds. PLoS ONE. 2015.
7. Gabriel MW et al. Anticoagulant rodenticides on our public and community lands: Spatial distribution of exposure and poisoning of a rare forest carnivore. PLoS ONE. 2012.
8. Mills E. The carbon footprint of indoor cannabis production. Energy Policy. 2012.
9. Warren GS. Regulating pot to save the polar bear: Energy and climate impacts of the marijuana industry. Columbia Journal of Environmental Law. 2015.
Hillary Rosner has covered science and the environment for National Geographic, The New York Times, Wired, Scientific American, Mother Jones, and many other publications.
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