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Benefit of thinning forests for spotted owls is not so clear-cut

Guest Column by Dominick DellaSala, PhD

The July 26 Oregonian editorial “Logging for spotted owls” dismisses decades of scientific research by touting one new study that suggests “heavy thinning” (aka, clear-cut lite) of forests could benefit spotted owls. Based on a single computer simulation, the new study suggests that intensive logging will magically prevent “catastrophic fires” such as the Biscuit that “wiped out” owls and other wildlife. This is unfounded.

The Biscuit fire did not destroy spotted owl territories, nor did it “consume” half a million acres of forests. More than half of the fire area actually burned with no, low or moderate fire severity, while a third was deliberately torched in what are called back burns set by firefighters trying to “control” the blaze. This fire was weather-driven, not fuel-driven, and occurred during a severe drought with gusting winds that created fire plumes up to 30,000 feet. Thinned areas burned as hot as those not thinned.

Klamath-Siskiyou country is no stranger to large fires. In fact, a Biscuit-like fire burned through the area in the late 1800s, and since then, fires of mixed severities (low, moderate, high) have repeatedly visited the landscape every 15 to 75 years. The renewal of plant communities — many of which are rare and fire-dependent — from repeat fires is part of the region’s globally distinct plant and wildlife richness. Mature evergreen forests with madrone and oak understories also have been shown to burn less severely than open forests, presumably because over time understory trees in these closed-canopy forests shade out flammable shrubs.

Ten years following the Biscuit fire, the landscape is a vibrant snag forest full of wildflowers, conifer seedlings, woodpeckers, songbirds and butterflies that began populating the fire area as the embers cooled (from nature’s rain, not firefighting). It was certainly not an ecological catastrophe. And while the fire influenced owl territories, its patchiness created a beneficial mixture of shrubby owl foraging areas with large dead and live trees left standing for nesting. Such snag forests are richer in plants and wildlife than even old-growth forests, and unlogged areas are rare because salvage logging, the true catastrophe in burned forests, typically damages them.

Decades of research on spotted owls and prey shows that logging is not as short-lived an impact as some might hope. This is because the owls roost and nest in closed-canopy, dense forests and so do many of the species’ prey. Opening up forests may encourage barred owls, a more aggressive competitor of spotted owls, thereby negating efforts by the U.S. Fish and Wildlife Service to contain this invading owl.

We agree with social reasons for thinning forests to reduce fuels, especially near buildings, and ecological reasons in highly flammable tree plantations. A recent report released by conservation groups and forestry experts, in fact, recommended a 44 percent annual increase in log volume as a byproduct of ecologically restorative actions in primarily tree plantations west of the Cascades. Until scientists have more definitive information on thinning effects on owls and prey, land managers would do best to stick with less ecologically risky and more scientifically supportable actions.

Dominick A. DellaSala is chief scientist of the Geos Institute in Ashland and was a member of the U.S. Fish and Wildlife Service spotted owl recovery team (2006-08). Also contributing to this essay: Monica L. Bond, principal scientist of the Wild Nature Institute and a member of the dry forest landscapes work group for the Northern Spotted Owl Recovery Plan; Dennis Odion, fire ecologist at the University of California at Santa Barbara; Randi Spivak, vice president of government affairs of the Geos Institute.

© 2012

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