How much marijuana is being grown in Humboldt County? We've all heard some store porch supposition on the subject, but there's little actual data to back it up. A recent article, published in the April edition of Environmental Research Letters, may help fill this vacuum.

University of California Berkeley research specialist Van Butsic, and Jacob C. Brenner, a professor at Ithaca College, spent almost a year analyzing satellite imagery from Humboldt County, counting greenhouses and extrapolating to come up with a figure of 4,428 grow sites spread over 60 watersheds. The project was inspired by what the researchers called "an urgent need for systemic empirical research."

"We were just interested in what's out there," Butsic said in a phone interview. "There were a lot of sensational articles. There was not a lot of evidence."

The team analyzed the images from the falls of 2012 and 2013, when plants would be easiest to spot. When they found a greenhouse, they flipped back through previous years to see how long it had been there. Their count estimated a 19-fold increase in greenhouses between 2004 and 2014. How do they know that these greenhouses were being used for weed? Common sense, the study posits – there was a simultaneous decrease in nursery crop production over those years. What else would they be used for? Greenhouse grows, according to the article, contain an average of about 86 plants, while outdoor grows contain about 45. Altogether, that adds up to an estimated 297,954 plants. So, we asked Butsic, are these numbers crazy?

"Not really," he said. "The main take home is that, as of 2012-2013, the total amount of land and water use for marijuana cultivation is actually quite small compared to other agricultural uses. That being said, the areas where it's taking place are not conducive for agriculture."

In other words, in the big picture, pot in Humboldt County is not sucking up the same amount of water large commercial agriculture operations might be. But it is being grown on increasingly subdivided parcels, on steep and eroding slopes, near sensitive fish habitat and out of sight from the kind of regulators who would, ostensibly, blow the whistle on this nonsense were it alfalfa or oranges.

Butsic said that calling pot "the new almond," as the New York Times once did, is a false analogy. But the water being used for marijuana is "coming from more complex circumstances" than traditional agriculture. And the study, as enlightening as it is, has some limitations. It assumes only one crop per year, but we know many cannabis farmers are doing multiple crops. And the research was conducted before the recent medical cannabis ordinance, which has brought a subsequent rush of new growers. Butsic confirmed that he is seeking funding for a new study that will compare production from the last four years.