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Insight into the environmental impacts of cannabis agriculture

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 Tuesday, June 21, 2016 at 10:20 AM
Tags: Agriculture (12), fish (6), land use (4), marijuana (8), policy (3), Water (72)

Don’t flush those fish!

Releasing aquarium fish into local waterways — or down the toilet — can damage aquatic ecosystems in a number of ways. The fish themselves can become an invasive species, they can disrupt habitats for other fish and aquatic species, and they may introduce secondary problems such as harmful pathogens or other aquarium species (seaweed, snails) into the waterways.

At least 13 of the 102 aquarium species that are imported into California have been introduced into California marine waters, according to a recent report by Susan Williams, professor in the Department of Evolution and Ecology at UC Davis and a marine ecologist the Bodega Marine Laboratory. These introduced species have a high success rate (69 percent) in establishing themselves.

Two very invasive species — the predatory lionfish and Caulerpa seaweed (aka “killer algae”) — have reportedly come from the aquarium trade. The lionfish, which has established itself along the East Coast where it eats smaller fish and threatens reef ecological systems, has not yet reached California waters, but the Caulerpa seaweed cost California more than $6 million to eradicate from two Southern California lagoons a decade ago.

At least 34 aquarium species were found to be potential invaders in California marine waters.

“Globally, the aquarium trade has contributed a third of the world’s worst aquatic and invasive species,” Williams said. "Lionfish are voracious predators in their native habitats, and in their invaded habitat any predator is a potential threat to the native ecosystem."

Williams’ advice: "To avoid releasing aquarium species into natural water, don’t dump your aquarium where they can become an expensive and harmful pests.”

She said that people should contact the vendor where the fish was purchased or the California Department of Fish and Wildlife to learn how to dispose of aquarium species responsibly.

Learn more:

  1. Complete UC Davis news release, by Kat Kerlin
  2. Our AmazingPlanet report
  3. Environmental News Network report
  4. Science on NBC News report
Posted on Wednesday, February 6, 2013 at 9:07 AM

Wine and fish for dinner? Water management required

The competition between farmers and fish for precious water in California is intensifying in wine country, say biologists at the University of California, Berkeley.

Juvenile steelhead trout, shown here in a small stream pool, are hit hard when water levels are low. (Ted Grantham photo)
A recently published study links higher death rates for threatened juvenile steelhead trout with low water levels in the summer and the amount of vineyard acreage upstream. Like salmon, steelhead trout migrate from freshwater streams to the ocean before returning to their birthplace to spawn. Steelhead trout in Southern California and the upper Columbia River are endangered, and several other populations, including those in Northern California, are threatened.

The researchers found that juvenile steelhead trout are particularly at risk during the dry summer season typical of California’s Mediterranean climate. Of the juvenile steelhead trout present in June, on average only 30 percent survived to the late summer. In years with higher rainfall and in watersheds with less vineyard land use, the survival of juvenile trout over the summer was significantly higher.

The researchers pointed out that salmon and trout conservation efforts have not adequately addressed summer stream flow. Previous studies have highlighted other limiting factors such as habitat degradation and water quality, while this study documented the importance of water quantity for restoring threatened populations.

Aerial view of vineyard agriculture in Sonoma County. Vineyards that divert water from streams used by juvenile salmon and steelhead trout could reduce their impacts by storing winter rainfall in small ponds such as the ones seen in this photo. (Adina Merenlender photo)
“Nearly all of California’s salmon and trout populations are on the path to extinction and if we’re going to bring these fish back to healthy levels, we have to change the way we manage our water,” said lead author Theodore Grantham, a recent Ph.D. graduate from UC Berkeley’s Department of Environmental Science, Policy and Management (ESPM). “Water withdrawals for agricultural uses can reduce or eliminate the limited amount of habitat available to sustain these cold-water fish through the summer.

Grantham says he is not suggesting we get rid of vineyards. “But we do need to focus our attention on water management strategies that reduce summer water use. I believe we can protect flows for fish and still have our glass of wine.”

Posted on Friday, May 18, 2012 at 10:20 AM
  • Author: Ann Brody Guy
  • Adapted from an article by: Sarah Yang
Tags: conservation (12), fish (6), salmon (8), water (72), wine (27)

Fish and wildlife funds disbursed in Marin

Dave Lewis
Fines levied for fish and wildlife violations in Marin County will fund a slate of programs to enhance local fish and wildlife resources and public education programs, according to the Marin Independent Journal.

The funding is being allocated by the Marin County Fish and Wildlife Commission, which is staffed by UC Cooperative Extension director and watershed management advisor Dave Lewis. He reported that reduced state and local allocations resulted in the commission limiting its recommendations for grant disbursements in 2011.

The nine grants, which ranged from $1,140 to the Friends of Corte Madera Creek Watershed to $300 for the Tyee Foundation, which raises and releases salmon in Tiburon, amounted to $7,033 in all. Also, $2,200 was allocated for administrative staff support of the commission. Last year, the panel distributed more than $24,000 to a dozen agencies.

Lewis said the commission gets about 18 percent of fish and game fine revenue to distribute after the state and courts take the lion's share of citation revenue generated in Marin. The funds support projects that promote restoration, sustainable use, management and related educational programs of the fish and wildlife resources in Marin County.

Posted on Monday, June 13, 2011 at 9:06 AM
Tags: Dave Lewis (1), fish (6), natural resources (8), wildlife (31)

UCCE expert featured in public TV video series

The public television affiliate in Los Angeles County, KCET, has posted a series of videos in its Departures series featuring UC Cooperative Extension natural resources advisor Sabrina Drill.

Departures is part of the KCET's Youth Voices digital literacy program, which engages high school students through workshops to become multimedia producers.

In this latest series of five videos, Drill and Camm Swift, a fishery biologist with the Natural History Museum, are filmed on the bank of the Los Angeles River chatting about the significant impact urban development, channeling, damns and introduction of non-native aquatic species has had on the ecosystem.

No native species still swim in the LA River and many riparian habitats - such as mudflats and wetlands - no longer exist.

"There's actually a big effort right now to do some large scale restoration of the LA River. The City of Los Angeles is heading that up," Drill said on the second video. "It's a long, long process, but they're in the feasibility study phase right now."

The student who produced the series, Mike Cadena, said in a commentary about the video series that joining the biologists on the riverbank was an amazing experience.

"What I was most amazed about was the river's potential for recreation. One of the biologists said that a long time ago there'd been plans to build all sorts of rec. centers and parks all along the river and this really got me thinking about what that would mean to all of Los Angeles," Cadena wrote.

KCET online series
KCET online series "Departures."

Posted on Tuesday, March 15, 2011 at 7:27 AM
Tags: fish (6), Los Angeles River (5), Sabrina Drill (12)

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