Fishers ‘n’ Fire

In keeping with this weeks California wildlife theme, this was in E&E news the 22nd of December.

Thinning forests in the southern Sierra Nevada mountains may cause some harm to key habitat for an isolated population of fishers, but such fuel reduction treatments likely will benefit the weasel-like mammals over the long run by reducing the risk of severe wildfire, a recent study concludes.

Forest managers have targeted dense stands in the Sierra National Forest and other public lands in the region for thinning in recent years, but they’re also required to help protect the fisher, which is a candidate for protection under the Endangered Species Act.

The study, published in the most recent issue of the journal Landscape Ecology, used computer models to simulate how different fuel reduction scenarios, including a no-treatment scenario, would affect fisher habitat over 60 years, compared with the potential effects of a major wildfire on the same habitat area. The authors concluded that while thinning could cause some damage to the fisher’s habitat, a high-intensity fire is a greater threat.

Description: Pacific fisher

Rare Pacific fishers rely on downed trees for denning, prompting questions about the effects of forest thinning on the animals’ habitat. But a recent study suggests that reducing the risk of destructive forest fires through fuel treatments will benefit the animals over the long run. Photo courtesy of Fish and Wildlife Service.

“Our simulations suggest that the direct, negative effects of fuel treatments on fisher population size are generally smaller than the indirect, positive effects of fuel treatments, because fuels treatments reduced the probability of large wildfires that can damage and fragment habitat over larger areas,” the study concludes.

Fuel treatments typically involve removing dead wood, which fishers use for denning, from the forest floor, said Robert Scheller, an assistant professor of environmental sciences and management at Portland State University in Oregon and the lead author of the study.

“It’s pretty important for them to have a safe place to raise a litter,” he said.

But a major fire would also damage the population’s habitat, “potentially over much broader areas than the treatments intended to reduce wildfire risks,” the study states. A large, super-hot fire would likely kill larger trees, shrink the forest canopy and burn up dead wood, all of which could adversely affect fishers.

“The long, relatively narrow arrangement of suitable habitat means that one or more large fires could burn across it and isolate fishers on either side of the burn,” the study states. “Because both fuels treatments and wildfires can negatively impact fisher habitat, this system exemplifies a probabilistic, risk-minimizing balancing act for forest and wildlife managers.”
Small, isolated population

Biologists estimate the southern Sierra Nevada fisher population at about 300 adults, most of which live in a narrow, isolated band across the western slope of the Sierras, south from Yosemite National Park to the mountain range’s southern tip.

Scheller added that while the study found that the overall benefits of fuel treatments probably outweigh the risks, such treatments are still something of a gamble: If no fire ever scorches the area, then the damage to the habitat from the fuel treatments would be for naught.

“The question is, ‘What are the odds of a fire coming through those areas that have been treated?'” he said.

The study is part of a broader effort from the Forest Service to figure out how to protect fishers while allowing for timber harvesting and fuel treatments in Sierra National Forest. Under the National Forest Management Act and Sierra Nevada Forest Plan, the Forest Service is to help maintain viable, well-distributed fisher populations.

The fisher once roamed from British Columbia to the southern Sierra, but historic fur trapping and logging reduced its range to three native populations — the southern Sierra Nevada, Northern California and southwestern Oregon — as well as a reintroduced population in Washington’s Olympic National Park.

Environmental groups say that logging continues to threaten the remaining fisher populations. Several groups have filed a lawsuit to try to force the Fish and Wildlife Service to add the West Coast population of the fisher to the endangered species list.

“Without protection from continued logging on private and federal lands, the fisher will go extinct,” said Craig Thomas, executive director of Sierra Forest Legacy.

Here’s a link to the study. I was looking around on the web for other information and ran across this look at the impacts of fuel treatments with some potential mitigation of their impacts by Truex and Zielinksi….

Also this one from May:

Kings River Fisher Project — Progress Report

Researchers Craig Thompson, Kathryn Purcell, James Garner and Rebecca Green from the Sierra Nevada Research Center of the U.S. Forest Service have just released a progess report on 72 radio-collared fisher which they have been studying since 2007. The project area is located in the Kings River area, west of Shaver Lake in the High Sierra Ranger District of the Sierra National Forest.

The purpose of this study is to learn more about fisher ecology including their habitat requirements, and to increase understanding about the effects of timber harvest and fuels treatments on select response variables of interest, including fishers and their habitat.

The report is too large to post here (30 MB) but it can be downloaded from this website until June 22. Here’s an excerpt from the summary:

“Using a combination of telemetry and scat dog data, we generated a preliminary density estimate of 13.4 fishers per 100 km². We observed reproductive activity for 79% of the adult females monitored during two breeding seasons, with 45 kits observed at 31 natal dens. We located an additional 64 maternal dens in a variety of structures. Survival rates ranged from 0.61 for subadult males to 1.0 for juvenile females, and predation accounted for 81% of all mortality. Genetically confirmed predators include mountain lion (40%), bobcat (40%), and coyote (20%).

We generated 95% kernel home range estimates of 1,113 ha for females and 4,522 ha for males. In agreement with most published literature, fishers were found in areas of higher canopy cover. However they were also found more often in areas with higher number of small (<20” dbh) trees, indicating that these trees may provide requisite structure and canopy. Fishers avoided edges, particularly with respect to resting sites, and were found on the lower portions of north facing slopes more often than any other topographic position. Fishers used a variety of tree species and structures for resting, with the most common choices being cavities in black oak and white fir. Diet was dominated by mammalian remains, though we documented a large diversity in food consumed including plants, birds, reptiles, and insects."

I wonder if fishers and Sierra red foxes (also in consideration as endangered species here) might be in competition for the same prey species?

Very interesting to me was the structure of the Sierra Nevada Adaptive Management Team here. With the public involved and the public discussion forum here. It is an intriguing approach and may be a good deal for $12 million over 7 years.

4 thoughts on “Fishers ‘n’ Fire”

  1. Every marking prescription I’ve seen in Sierra Nevada National Forests has built-in protections for the Pacific Fisher. Canopy coverage is a specification that determines a lot of the “future desired condition” of evenly spaced, healthy and fast-growing trees that form a resilient forest, supporting endangered species.

    This sentence bothers me, though. “If no fire ever scorches the area, then the damage to the habitat from the fuel treatments would be for naught.” This statement shows a poor understanding of fire ecology and natural history in the Sierra Nevada. Many areas locally have had more than ten wildfires in the last 100 years, documented by tree rings and fire scars.

    If there are more than 72 fishers in their relatively small study area, it doesn’t seem to me that these animals are really “endangered”, given that logging practices have radically changed, and given that annual timber volumes have dropped precipitously, in the area. If widespread clearcutting and highgrading hasn’t killed off the fisher, what makes people think that modern-day, cutting-edge thinning projects will cause “extinction”? Once again, trees bigger than 30″ dbh are fully protected from logging, with clearcutting and highgrading being voluntarily banned by the Forest Service since 1993.

  2. Foto-

    That’s what struck me as interesting. Is there anywhere where there is “never” a fire (other than above treeline, maybe?) And if there isn’t a fire, don’t fuel loadings simply build up until that point (there isn’t some other factor that removes them, is there)?
    I was also interested (albeit not enough to go back to the original article) in this statement from the King’s River Project Report above…

    “However they were also found more often in areas with higher number of small (<20” dbh) trees, indicating that these trees may provide requisite structure and canopy. " I think they mean "more often than expected", but not sure exactly.

    Here's also more fishers relocated and the 2010 report .

  3. This study would appear to contradict the recent results confirming that thinning reduces carbon storage compared to wildfire. This fisher study actually uses biomass as a proxy for fisher habitat, so how can it show increased biomass when other studies show the opposite? My guess is that the fisher study assumes that fire is highly likely to occur after thinning treatments and fails to consider the fact that treatments are unlikely to experience fire and many acres must be treated in order to achieve slight reductions in wildfire. See

  4. Tree- I think that ensuring fisher habitat through time and tracking carbon may be different. I think fisher habitat is probably easier for the human brain to understand than carbon fluxes through time. In my simple brain, you have carbon in the soil, vegetation, etc. and then you lose some from different activities but when you lose it the vegetation sequesters more. So you need to keep summing gained and lost through time.

    Fishers are easier. you have some quality of habitat at any point in time. Fires will happen (unless there are areas where it won’t; not sure where that would be, in the Sierra); if there are large amounts of fuel (in general), the impact to habitat will be worse than if the fire can run through at the ground with lower levels of fuel.

    Now my question is if the fishers are currently restricted in area, couldn’t fuel treatments be targeted for where they are, to protect their key habitat? If there habitat is close to where we would want to do fuel treatments anyway for communities, wouldn’t that be a good thing?

    If they’re dispersed throughout the Sierra, then why wouldn’t the guidelines above that Foto mentions be appropriate and sufficient?

    When the authors (Campbell, et al.) say, in the summary, that
    “Our review reveals high C losses associated with fuel treatment, only modest differences in the combustive losses associated with high-severity fire and the low-severity fire that fuel treatment is meant to encourage, and a low likelihood that treated forests will be exposed to fire. ”

    There is something missing..from this summary statement. In many places where the climate is dry, it is a long long time before dead trees will not be good fuel due to decomposition. So fuel loadings persist for a long long time. Further, it has been claimed that the climate is getting hotter and drier due to climate change, and that there will be more/more intense fires. So I don’t know how we could claim about the future that there will be a low likelihood that treated or untreated forests will be exposed to fire. Like I said, I think there is an added complexity of thought that didn’t come through in the summary.


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