In fact the eco impact of growing weed has never really been properly measured given cultivation of the plant has been illegal in the past.
However, a study from the University of California Berkeley Cannabis Research Center has determined that licensed cannabis cultivation operations use less water than previously thought. Water use is a particularly pertinent issue given the drought issues in many areas of the USA, especially California where this research took place.
Researchers from the center began studying water use by cannabis growers following California’s legalization of recreational marijuana, which occurred in 2016.
The investigators collected their data from the water use reports of licensed cannabis growers across California, as well as from anonymous farmer surveys.
The survey results found that cannabis farmers are irrigating their crops with water from multiple sources that include streams, wells, captured rainwater, springs, and municipal water systems. For regulated cannabis operations, water use was mainly from groundwater wells.
Most surprisingly though, was that cannabis wasn’t particularly thirsty relative to other crops.
“Legal, outdoor production uses about the same amount of water as a crop like tomatoes,” researcher Van Butsic, a co-director at the Cannabis Research Center, told local media.
Another way to look at thirstiness is to consider how much output is produced by a single gallon of water, and here, cannabis is arguably very cost efficient. According to Natalynne DeLapp, executive director of the Humboldt County Growers Alliance, the average size of a cannabis farm in Humboldt County is about half an acre, while most farms for other agricultural products can cover hundreds or even thousands of acres.
“For other crops like tomatoes, lettuce, or almonds, a gallon of water produces between a tenth of a cent to two cents of value in yield,” DeLapp told High Times. “For cannabis, a gallon of water produces nearly $7 worth of value. In that sense, cannabis is by far the most water-efficient agricultural product in California.”
Sources: High Times, Science Direct