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Legalizing recreational marijuana dramatically increases growth of the plant, which is bad for the environment.

According to a 2021 review, “Results show that both indoor and outdoor cannabis growing is water-intensive. The high water demand leads to water pollution and diversion, which could negatively affect the ecosystem. Studies found out that cannabis plants emit a significant amount of biogenic volatile organic compounds, which could cause indoor air quality issues. Indoor cannabis cultivation is energy-consuming, mainly due to heating, ventilation, air conditioning, and lighting. Energy consumption leads to greenhouse gas emissions. Cannabis cultivation could directly contribute to soil erosion. Meanwhile, cannabis plants have the ability to absorb and store heavy metals. [279]

Additionally marijuana cultivation results in deforestation, habitat destruction, and river diversion. [140] [142]

Cannabis plants require nearly double the amount of water needed to grow grapes or tomatoes. Rosamond Naylor, Senior Fellow at the Stanford Woods Institute for the Environment, said, “Taking water directly from rivers and streams in the summer [to grow marijuana] not only reduces the water available for agriculture but also threatens wildlife species… Regardless of the legal status of marijuana, the way we are currently managing its impacts on water and wildlife in California just doesn’t work.” [142] [144] [145] [142] [144] [145]

Because remains an illegal drug at the federal level, “the United States Environmental Protection Agency (EPA) has not approved any pesticides for use on the plant.” This lack of guidance has resulted in some growers using “banned pesticides and blood thinners/rat poisons against crop-eating mammals” and not properly disposing of chemicals and waste. Further, growing marijuana results in a number of waste streams, including waste similar to food manufacturers, agricultural waste, mercury-containing waste (as a result of UV light use), toxic and flammable waste from THC extraction chemicals. Uneducated growers, or those without state-supported guidelines may be destroying their local environments. [280]

Legal indoor growing also requires a lot of electricity for lighting, heating, and ventilation. These “heavy-load electric devices” include UV lights that are powered on 16 or more hours daily, irrigation systems, HVAC (air conditioning and heating) systems, and air filter systems. In just three years after legalization, Denver growers doubled their electric use, accounting for almost 5% of the 2.8 million city residents’ power use. [280]

Derek Smith, executive director of the non-profit Resource Innovation Institute, explains, “The reality is this industry has been in the shadows for a long time [and thus, many newly legal growers are]… using, in some cases, the same technology that was used in basements in the black market days just blown up to 50,000 square feet – very hot lights, very inefficient HVAC, very little ventilation.” [181]

Not only do old and new technologies seriously strain an already stuggling power grid, but the energy consumption from growing marijuana also produces an amount of greenhouse gas emissions equal to that of 3.3 million cars each year. As a Jan. 2022 Mother Jones article jabs, “Dude, your cannabis habit has an epic carbon footprint.” The article notes, “Studying more than 1,000 locations across the United States, researchers from Colorado State University calculated the median emissions of growing one kilogram of cannabis to be about 3,600 kilograms of CO2 equivalent emissions. The amount varies from roughly 2,300 to 5,200 kilograms of emissions per kilogram grown depending on location. To put that in perspective, a kilogram of tomatoes grown in a British Columbia [Canada] greenhouse heated with natural gas emits roughly two kilograms.” [141] [282]

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