Thinning Harms Flighty Rodents
Oregonians may not know it, but our state’s forests are riddled with wide-eyed, nocturnal, gliding mammals. The northern flying squirrel serves many ecological functions in Pacific Northwest forests, and is considered to be a “keystone species.” It is a vital part of the diet of the endangered species listed northern spotted owl, and a new study shows that flying squirrels are negatively affected by commercial thinning of timber.
Commercial thinning in regenerating stands of previously logged Douglas fir is supposed to provide a small amount of lumber, reduce fire danger and give trees room to develop old-growth characteristics in which species like the flying squirrel and the spotted owl thrive.
However, a recent study by scientists from OSU and the U.S. Geological Survey found that the thinning actually reduces the density of flying squirrels.
Researchers used live-capture traps to catch and count flying squirrels in the Willamette National forest, east and southeast of Eugene. “Our research makes it clear that densities of northern flying squirrels are particularly sensitive to thinning in young Douglas fir forests for at least 12 years after treatment,” researchers Tom Manning, Joan Hagar and Brenda McComb conclude.
This study demonstrates that forest thinning presents a tradeoff: It will benefit native species in the long-term, but on a short-term basis it is detrimental to flying squirrels (and therefore possibly to spotted owls).
Hagar says that these findings demonstrate the high level of ecological complexity at play when it comes to forest restoration. “No matter what we do in the forest, there is a positive affect on some species and a negative affect on other species,” she says. Although this study found forest thinning to reduce flying squirrel population densities, Hagar says she has conducted other research indicating that thinning is beneficial for the density of native songbirds. “Forest thinning is a great management tool as long as were are well-aware of the impact,” Hagar says.
This study shows that, in the delicate balance of forest ecosystems, the path to restoration is not clear-cut.