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How to study cannabis

Soon after Van Butsic arrived in California in 2013 to join UC Agriculture and Natural Resources, he noticed a pattern. “Fire, water and weed are the three land-use issues that come up no matter who I talk to in this state,” he said. Fire and water were well-covered by UC and other researchers already. But cannabis looked to be an unexploited niche.

UCCE Assistant Specialist Van Butsic uses satellite imagery to analyze the environmental impacts of cannabis production.

UCCE Assistant Specialist Van Butsic uses satellite imagery to analyze the environmental impacts of cannabis production.

So Butsic, a UC Cooperative Extension (UCCE) assistant specialist in land systems science in the UC Berkeley Department of Environmental Science, Policy and Management, decided to build part of his research portfolio around understanding the scope, intensity and landscape impacts of cannabis cultivation in California (a research paper from another area of his research, ecosystem service valuation, appears on page 81 of this issue).

While the environmental impacts of cannabis production have drawn substantial media attention, and though it is by many estimates the state's most valuable crop, data beyond anecdotes is scarce.

Butsic attacked the problem by visually analyzing satellite-based imagery, identifying remote plantations and greenhouses in Humboldt County and mapping them using GIS.

This approach required many hundreds of hours of manual inspection of satellite images, and one of the first challenges was figuring out how to do this labor-intensive work. It wasn't difficult to find UC Berkeley undergraduates interested in working for course credit. Nearly 25 students have now contributed to the project, and two (so far) have moved on to full-time GIS jobs after graduation. An anonymous nonprofit organization provided financial support for a part-time staff researcher and to purchase more recent high-resolution satellite data.

This series of satellite images shows the development of a greenhouse complex in a Humboldt County forest. Using satellite imagery in combination with GIS layers showing topopgraphy, watercourses, zoning and other variables, Butsic and his colleagues can characterize cannabis production sites in a variety of ways, such as average slope, proximity to streams, and whether they are located on land zoned for agriculture.

This series of satellite images shows the development of a greenhouse complex in a Humboldt County forest. Using satellite imagery in combination with GIS layers showing topopgraphy, watercourses, zoning and other variables, Butsic and his colleagues can characterize cannabis production sites in a variety of ways, such as average slope, proximity to streams, and whether they are located on land zoned for agriculture.

The team has built a GIS data layer for about half of Humboldt County's land area, identifying roughly 300,000 cannabis plants (equivalent to a wholesale value of perhaps $150 million) based on 2012 imagery, with an updated estimate now in the works. The data layer enables a variety of analyses — from the zoning of the land used by cannabis growers (only about a quarter of the 1,429 grows identified were on land zoned for agriculture); to the slope of cannabis production plots, a factor influencing erosion (almost a quarter are on very steep ground, with slope exceeding 30%); to proximity to salmon streams (more than 200 grows were found within 100 meters of critical habitat for steelhead and chinook salmon) (Butsic and Brenner 2016).

Butsic and his colleagues identified approximately 4,400 grow sites in their research. Five percent of those, including the site pictured above, were within 100 meters of salmon streams.

Butsic and his colleagues identified approximately 4,400 grow sites in their research. Five percent of those, including the site pictured above, were within 100 meters of salmon streams.

Butsic estimates the absolute volume of water used to irrigate cannabis to be fairly modest — on the order of a few thousand acre-feet. But that figure probably understates the habitat impact of water diversions; water is withdrawn from small watersheds during summer months when water is scarce, and some creeks are known to have been completely dewatered.

The information is helping to inform local debates. Humboldt County recently adopted an ordinance requiring all new cannabis grows to be developed on land zoned for agriculture (existing grows on nonagricultural land are grandfathered in). This policy raises concerns about rapid inflation of agricultural land, as cannabis growers bid up prices beyond what other farm or livestock operations can support. Butsic's work provides insights into the characteristics and geography of lands that are likely to be developed for cannabis production.

Forest fragmentation occurs when cannabis growers clear land and build roads to access their grow sites. The Butsic team's analysis indicates that 68% of grows were located more than 500 meters from developed roads.

Forest fragmentation occurs when cannabis growers clear land and build roads to access their grow sites. The Butsic team's analysis indicates that 68% of grows were located more than 500 meters from developed roads.

Related to this issue, Butsic and several Humboldt County–based UCCE academics — County Director Yana Valachovic, Area Fire Advisor Lenya Quinn-Davidson, and Livestock and Natural Resources Advisor Jeffery Stackhouse — are currently surveying Humboldt County landowners about cannabis-related land use issues.

Butsic's next steps include continued mapping of cannabis production in California, with Mendocino County to be completed by the end of 2017. Given the uncertainty around federal restrictions on cannabis production under the Trump administration, Butsic said it's difficult to predict what the most essential research questions surrounding cannabis will be. Nonetheless, “by continuing to document on the ground patterns of cannabis production, we will be in a position to answer those questions,” he said.

Posted on Wednesday, August 2, 2017 at 3:07 PM
  • Author: Jim Downing

Insight into the environmental impacts of cannabis agriculture

Reposted from the UCANR Green Blog

Google Earth Image of a cannabis grow site. The resolution of Google Earth images allowed the researchers to detect marijuana plants that were previously missed with other remote sensing techniques.
 

As policy liberalization rapidly transforms the multi-billion-dollar cannabis agriculture industry in the United States, the need for regulation and assessment of environmental impacts becomes increasingly apparent. 

A recent study led by UC Cooperative Extension specialist Van Butsic used high resolution satellite imagery to conduct a systematic survey of cannabis production and to explore its potential ecological consequences. 

Published this spring in Environmental Research Letters, the study focused on the “emerald-triangle” in northern California's Humboldt, Mendocino, and Trinity counties, which many believe is the top cannabis-producing region in the United States.

The UC Berkeley-based Butsic and his co-author Jacob Brenner used Google Earth imagery to locate and map grow sites (both greenhouses and outdoor plots) in 60 watersheds. Most cannabis grow sites are very small, and have gone undetected when researchers used automated remote sensing techniques, which are commonly used to detect larger changes such as deforestation.

“We chose to use fine-grained imagery available in Google Earth and to systematically digitize grows by hand, identifying individual plants. Most plants stand out as neat, clear, little circles,” said Brenner, who is on the faculty of the Department of  Environmental Studies and Science at Ithaca College. “The method was laborious — it took over 700 hours — but it proved to be highly accurate.”

Butsic and Brenner paired their image analysis with data on the spatial characteristics of the sites (slope, distance to rivers, distance to roads) and information on steelhead trout and Chinook salmon, both of which are listed as threatened species under the federal Endangered Species Act. These and other species are vulnerable to the low water flows, soil erosion, and chemical contamination that can result from nearby agriculture.

Results of the study show 4,428 grow sites, most of which were located on steep slopes far from developed roads. Because these sites will potentially use significant amounts of water and are near the habitat for threatened species, Butsic and Brenner conclude that there is a high risk of negative ecological consequences.

“The overall footprint of the grows is actually quite small [~2 square kiliometers], and the water use is only equivalent to about 100 acres of almonds,” says Butsic, who is in the Department of Environmental Science, Policy, and Management at Berkeley. According to Butsic, California currently has more than one million irrigated acres of almonds.

He stresses that the issue lies in the placement of the sites: “Close to streams, far from roads, and on steep slopes — cannabis may be a case of the right plant being in the wrong place.”

Last year, California legislature passed laws designed to regulate medical marijuana production, and state voters will weigh in on whether to legalize recreational marijuana this coming fall. Given these changes as well as the profitability of cannabis production, Butsic expects that marijuana cultivation will expand into other sites with suitable growing conditions throughout the region. He and Brenner assert that ecological monitoring of these hotspots should be a top priority.

Bills recently signed into law by Governor Jerry Brown have made some advances in this direction — requiring municipalities to develop land use ordinances for cannabis production, forcing growers to obtain permits for water diversions, and requiring a system to track cannabis from when it is first planted until it reaches consumers.

But the researchers say that regulation will likely be a constant challenge because it will rely on monitoring procedures that are just now emerging, as well as voluntary registration from producers and budget allocation from the state for oversight and enforcement.

“Some of the same fundamental challenges that face researchers face regulators as well, primarily that cannabis agriculture remains a semi-clandestine activity,” says Brenner. “It has a legacy of lurking in the shadows. We just don't know — and can't know — where every grow exists or whether every grower is complying with new regulations.”

 
Posted on Saturday, June 25, 2016 at 10:40 AM
  • Author: Julie Van Scoy
 
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