Earth Talk: Marijuana and the environment

Dear EarthTalk: What are the environmental impacts of the widespread legalization of marijuana in recent years?-- Mac Styles, Tallahassee, Florida

Answer: Cannabis is an increasingly popular recreational and medicinal drug. As more states legalize cannabis for some medicinal and recreational uses, cannabis production is on the rise.

On average, cannabis requires double the amount of water than food staples like corn, soybean and wheat. Over 60% of marijuana grown in the United States originates from California. Additionally, California produces nearly 75% of the nation's fruits and nuts and over 33% of its vegetables. California agriculture is significantly supported by aquifers, surface water diversion, springs and rivers.

The rising demand for cannabis may exacerbate water scarcity, divert freshwater from essential agriculture and municipal needs, and harm water ecosystems by altering stream flows.

A single pound of commercial marijuana product correlates to over 4,600 pounds of carbon dioxide emissions produced. Additionally, cannabis plant matter has been found to contain high concentrations of biogenic volatile organic compounds, especially monoterpenes, which have been linked to increases in ground-level ozone pollution and particulate matter that can lead to severe health issues.

Further, cannabis cultivation is often enhanced by pesticides and ammonia-rich fertilizers that are used to supplement the plant’s high nitrogen requirement. The ammonia frequently volatilizes into the atmosphere, bonding with nitrogen oxides to produce particulate matter. Runoff from these inputs also causes soil acidification, water eutrophication, oxygen depletion and harm to aquatic life.

Indoor planting facilities require significant energy for lighting, heating, ventilation and...