From historic trapping and logging in Southern Oregon and Northern California to present day poisoning from rodenticides used on illegal marijuana farms, fishers have faced many threats over the years. The latest effects to be studied are wildfires and salvage logging.
A new paper published this week in the journal Ecosphere studied the effect of three mixed severity wildfires from 2014-2016 on fishers in the Klamath-Siskiyou region.
“Limited evidence suggests that fire may decrease fisher occupancy but no study has empirically estimated the effects of wildfires on fisher populations,” the authors wrote.
The largest population of fishers in the Western U.S. exists along the Oregon-California border, and it’s the site of a long-term fisher monitoring project.
“Because we have all the data that occurred before the fires, we can say with some certainty that the fires did disrupt this environment and the number of fishers did decline following those fires,” says David Green, a researcher with the Institute for Natural Resources at Oregon State University and the lead author of the paper.
Green and his co-authors found that wildfires and post-fire logging reduced fisher populations by 27% in a 465-square kilometer survey area.
Their research suggests salvage logging contributed to the species’ decline by removing dead trees that fishers use for protection from predators like bobcats and mountain lions.
In 2019 the West Coast population of fishers was proposed for protection under the Endangered Species Act by the U.S. Fish and Wildlife Service. But the Southern Oregon and Northern California population was denied that protection by the Trump administration.
Green says they were surprised to learn from their research that fisher populations declined because of low-, medium- and high-severity wildfires.
“Fishers, in some ways, have to have been adapted to fires,” Green says. “This isn’t something that’s super novel to them. But the types of fires that are occurring and the frequency is different than historical regimes.”
The added intensity of climate change on wildfire, plus habitat disruption from salvage logging may be altering the landscape beyond what fishers are adapted to, he says.
Green says more research is needed to know whether the fires and logging activities will permanently impact fishers or if their numbers will rebound.
