Fire suppression and illegal marijuana cultivation threaten rare Pacific fishers

 

The Pacific fisher, a small, carnivorous forest-dwelling mammal, is a candidate for listing under the federal Endangered Species Act this year, and big wildfire could be to blame – or rather, the lack of it.

Ecologist Chad Hanson’s recent research on the fisher population of the southern Sierra Nevada shows that the animals – aptly described as “the love child of a ferret and a wolverine” – actually seek out post-fire habitat, especially areas that have burned at higher severity, where most of the trees are killed. In a 2013 study, the first to ever examine the relationship between fishers and fire, Hanson used dogs trained to detect Pacific fisher scat, tracking where they eat, sleep, raise their young and otherwise use forest habitat. He has yet to decipher exactly why fishers need post-fire habitat, but he suspects that the combination of downed logs, standing burned trees and natural regrowth create an ideal environment for the small mammals that fishers prey on.

5788241740_df3d2d4048_o.png
A fisher, which has been proposed for the endangered species list. Image courtesy the USFS Region 5 Flickr.

The idea that there might be a wildfire deficit might seem odd in a time when the consensus among fire managers appears to be that we are experiencing increasingly frequent and more intense wildfire in the West. But a study released this month, co-authored by Hanson, says that contrary to commonly held belief, the majority of Western forests actually had more high-severity fires before fire suppression began 100 years ago than they do now. It seems ironic, then, that current Western forest management practice is based on the belief that only low- to moderate-severity fire was common before fire suppression, and that high-severity fire is a product of that suppression, exacerbated by climate change, and is largely damaging to wildlife and habitat. So high-severity fire – which burns 70 to 100 percent of woody vegetation and climbs from the ground to the treetops – is prevented as a matter of policy.

The means of suppression can include tree thinning designed to prevent high-severity fire, which Hanson said often means intensive commercial logging that removes up to 80 and even 90 percent of the trees in a given area. Managers think of this type of suppression, Hanson said, as “a sort of lesser-of-two-evils approach” for the fisher.

DinkeyLoggingPhoto2.jpg
This mechanical thinning project was conducted in previously suitable Pacific fisher habitat in California's Sierra National Forest. Ironically this commercial logging project was promoted as a project designed to restore fisher habitat, but Hanson said the homogenized conditions it created are exactly the opposite of what scientific studies are concluding Pacific fishers need. Photo courtesy Chad Hanson.

“There’s acknowledgement that the logging projects are not good for fisher habitat – that it actually degrades it,” he said. But forest managers typically think that thinning is necessary to save the species from the greater harm of fire.

Before Hanson, nobody had tested the assumption that high-severity fire is harmful to fishers, and his research shows that the post-fire forest is in fact a significant part of the fisher’s home range. This has to do with what ecologists call the “bed and breakfast” phenomenon. 

“(Fishers) get certain habitat requirements from the dense old forests,” like denning and nesting, Hanson said. “But they also get certain habitat requirements (like food) from the complex early seral forest – what we call snag forest habitat – created by high-severity fire. It’s the juxtaposition of those two things that really gives them that range of what they need.”

FisherScatDogStudyPhoto4July2012.jpg
The McNally fire area, where Hanson's fisher scat surveys were conducted, shows the complex post-fire forest habitat that fishers use. The many standing snags, downed logs, and montane chaparral patches and natural conifer regeneration provide the biomass and structural that make for good habitat for the fisher's small mammal prey. Photo courtesy Chad Hanson.

But the dense forests of Humboldt, Mendocino and Trinity counties in California are posing a second major threat to the fisher. Illegal marijuana growers in what's come to be known as the “Emerald Triangle,” the largest cannabis-producing region in the U.S., replace patches of dense forest with marijuana plantations, and use an anticoagulant rat poison to keep rodents away from their weed. (Rats are probably drawn to camp trash and food, but will also chew on the pot plants themselves.) Research by wildlife pathologist Mourad Gabriel shows that the rat poison is also killing fishers, who eat dying poisoned rats and possibly even eat the poison directly. Gabriel has spent years tracking fishers deep in the remote forests of California, and a recent Mother Jones story reported that at least 48 of the 60 fishers collected by Gabriel tested positive for the rodenticide. Death by this poison is unmistakable: the anticoagulant properties cause blood to pool in the fisher’s stomach, and the poison is detectable in its blood. The illegal pot plantations are the only nearby source of the poison, which is banned for agricultural use. Gabriel has said that on a single plant, he’s seen growers use up to 50 times more poison than would kill a 500-pound lion.

Screenshot20140226at12.28.54PM.png
The historical range of the Pacific fisher in California has been significantly reduced over time. Dark green shows its current region and white patches indicate where it was once much more common. Courtesy California Department of Fish & Game. Click for larger image.

It’s possible that the absence of post-fire snag forest habitat may even be pushing fishers to seek food around the illegal pot plantations – where there are plenty of rats to eat – hidden in the type of dense forests fishers typically use for their dens and nests. But despite the acute danger from rodenticide, Hanson said that the greater threat is still the ongoing lack of high-severity fire. Indeed, past petitions from environmental groups to list the fisher as an endangered species emphasize historic habitat loss due to logging and fire suppression as the underlying threat.

It’s still unclear whether the combined impact of too much rodenticide and too little high-severity fire will be more than the species can handle. Limited relocation efforts have been underway for several years. California’s Northern Sierra Fisher Reintroduction Project, for instance, relocates fishers to habitat in the southern Cascades and northern Sierra Nevada, where an agreement between a private timber company and U.S. Fish and Wildlife offers them protection. But these fragmented efforts are not an ideal solution. Manson said the stress of relocation can be traumatic, and it could take years to determine whether a relocated population will survive.

“All species are adaptable in some sense, but I don’t think we can call the fisher a habitat generalist,” Hanson said. “Based upon the data, it’s actually quite specific in its habitat.”

In the meantime Hanson wants to see the fisher make the federal endangered species list. And such a listing might just carry enough weight to start to tip wildfire management policy in a new direction across the West, by adding to a growing group of species known to depend on snag forest habitat, like the threatened northern spotted owl and imperiled black-backed woodpecker. Hanson’s fire-severity study recommends a policy shift toward reintroducing high-severity fire on public forested land, while creating a safe buffer between public forests and private housing.

Fishers are already listed as endangered in the state of Washington and as “sensitive” in Oregon, but are not listed at all in California. A federal endangered species listing decision probably won’t be made until September of this year. Hopefully the Pacific fisher won’t be left high and dry, between wildfire and weed.

Christi Turner is an editorial intern at High Country News. She tweets @christi_mada.

High Country News Classifieds
  • PLANNED GIVING OFFICER
    National Parks Conservation Association (NPCA), the nation's oldest and largest national parks nonprofit advocacy organization seeks a Planned Giving Officer. Do you find energy in...
  • DEPUTY DIRECTOR
    The Methow Valley Citizens Council has a distinguished history of advocating for progressive land use and environmental values in the Methow Valley and Okanogan County...
  • ACTING INDIGENOUS AFFAIRS DESK EDITOR
    High Country News is seeking an Acting Indigenous Affairs Editor to oversee the work of our award-winning Indigenous Affairs Desk while our editor is on...
  • GRANTS PROGRAM DIRECTOR
    The Cinnabar Foundation seeks an enthusiastic, team-oriented and knowledgeable Grants Program Director to work from their home in Montana. Established in 1983, the Cinnabar Foundation...
  • ARTEMIS PROGRAM MANAGER
    The Artemis Program Manager will work with National Wildlife Federation sporting and public lands staff to change this dynamic, continue to build upon our successful...
  • ALASKA SEA KAYAK BUSINESS FOR SALE
    Well-known and successful sea kayak, raft, hike, camp guiding & water taxi service. Sale includes everything needed to run the business, including office & gear...
  • MEMBERSHIP AND EVENTS PROGRAM COORDINATOR
    Great Old Broads for Wilderness seeks a detail-oriented and enthusiastic Membership and Events Coordinator to join our small, but mighty-fun team to oversee our membership...
  • PROGRAM DEVELOPMENT FACILITATOR
    ABOUT THE HIGH DESERT MUSEUM Since opening in 1982, HIGH DESERT MUSEUM has brought together wildlife, culture, art and natural resources to promote an understanding...
  • LAND STEWARD, ARAVAIPA
    Steward will live on-site in housing provided by TNC and maintains preserve areas frequented by the visiting public and performs land management activities. The Land...
  • DEVELOPMENT WRITER
    Who We Are: The Nature Conservancy's mission is to protect the lands and waters upon which all life depends. As a science-based organization, we create...
  • CONNECTIVITY SCIENCE COORDINATOR
    Position type: Full time, exempt Location: Bozeman preferred; remote negotiable Compensation: $48,000 - $52,000 Benefits: Major medical insurance, up to 5% match on a 401k,...
  • EXECUTIVE ASSISTANT
    ArenaLife is looking for an Executive Assistant who wants to work in a fast-paced, exciting, and growing organization. We are looking for someone to support...
  • EXECUTIVE DIRECTOR
    The Mountain Lion Foundation is seeking an Executive Director. Please see our website for further information - mountainlion.org/job-openings
  • WASHINGTON DC REPRESENTATIVE
    Position Status: Full-time, exempt Location: Washington, DC Position Reports to: Program Director The Western Organization of Resource Councils (WORC) is seeking a Washington, DC Representative...
  • REGIONAL CAMPAIGN ORGANIZER
    Position Title: Regional Campaign Organizers (2 positions) Position Status: Full-time, exempt Location: Preferred Billings, MT; remote location within WORC's region (in or near Grand Junction...
  • DEVELOPMENT DIRECTOR
    Driggs, ID based non-profit. Full time. Full job description available at tvtap.org. Submit cover letter and resume to [email protected]
  • ENVIRONMENTAL AND CONSTRUCTION GEOPHYSICS
    - We find groundwater, buried debris and assist with new construction projects for a fraction of drilling costs.
  • SPRING MOUNTAINS SOLAR OFF GRID MOUNTAIN HOME
    Located 50 miles northwest of Las Vegas, Nevada in the pine forest of Lee Canyon at 8000 feet elevation. One of a kind property surrounded...
  • MAJOR GIFTS MANAGER - MOUNTAIN WEST, THE CONSERVATION FUND
    Cultivate, solicit and steward a portfolio of 75-125 donors.
  • NATURE'S BEST IN ARAVAIPA CANYON
    10 acre private oasis in one of Arizona's beautiful canyons. Fully furnished, 2123 sq ft architectural custom-built contemporary home with spectacular views and many extras....