Send Orders for Reprints to reprints@benthamscience.net The Open Ecology Journal, 2014, 7, 37-51 37 1874-2130/14 2014 Bentham Open Open Access Effects of Fire and Commercial Thinning on Future Habitat of the Northern Spotted Owl Dennis C. Odion 1,* , Chad T. Hanson 2 , Dominick. A. DellaSala 3 , William L. Baker 4 and Monica L. Bond 5 1 Earth Research Institute, University of California, Santa Barbara, California. 93106. Environmental Studies Department, Southern Oregon University, Ashland, Oregon, 97520 2 Earth Island Institute, 2150 Allston Way, Suite #460, Berkeley, California, 94704 3 Geos Institute, Ashland, Oregon, 97520 4 Program in Ecology and Department of Geography, University of Wyoming, Laramie, WY, 80271 5 Wild Nature Institute, PO Box 165, Hanover, NH 03755 Abstract: The Northern Spotted Owl (Strix occidentalis caurina) is an emblematic, threatened raptor associated with dense, late-successional forests in the Pacific Northwest, USA. Concerns over high-severity fire and reduced timber harvesting have led to programs to commercially thin forests, and this may occur within habitat designated as “critical” for spotted owls. However, thinning is only allowed under the U.S. Government spotted owl guidelines if the long-term benefits clearly outweigh adverse impacts. This possibility remains uncertain. Adverse impacts from commercial thinning may be caused by removal of key habitat elements and creation of forests that are more open than those likely to be occupied by spotted owls. Benefits of thinning may accrue through reduction in high-severity fire, yet whether the fire- reduction benefits accrue faster than the adverse impacts of reduced late-successional habitat from thinning remains an untested hypothesis. We found that rotations of severe fire (the time required for high-severity fire to burn an area equal to the area of interest once) in spotted owl habitat since 1996, the earliest date we could use, were 362 and 913 years for the two regions of interest: the Klamath and dry Cascades. Using empirical data, we calculated the future amount of spotted owl habitat that may be maintained with these rates of high-severity fire and ongoing forest regrowth rates with and without commercial thinning. Over 40 years, habitat loss would be far greater than with no thinning because, under a “best case” scenario, thinning reduced 3.4 and 6.0 times more dense, late-successional forest than it prevented from burning in high-severity fire in the Klamath and dry Cascades, respectively. Even if rates of fire increase substantially, the requirement that the long-term benefits of commercial thinning clearly outweigh adverse impacts is not attainable with commercial thinning in spotted owl habitat. It is also becoming increasingly recognized that exclusion of high-severity fire may not benefit spotted owls in areas where owls evolved with reoccurring fires in the landscape. Keywords: Fire rotation, forest regrowth rate, forest thinning, future habitat, habitat loss, late-successional forest, policy implications, severe fire, spotted owl. INTRODUCTION Conservation of the emblematic Northern Spotted Owl (Strix occidentalis ssp. caurina) in the Pacific Northwest of North America has become a global example of balancing conflicting land management goals (DellaSala and Williams 2006). Concern over degradation of the owl’s dense, late- successional forest habitat led to the 1994 Northwest Forest Plan (NWFP). The NWFP shifted management on ~100,000 km 2 of federal USA forestlands from an emphasis on resource extraction to embrace ecosystem management and *Address correspondence to this author at the Earth Research Institute, University of California, Santa Barbara, California. 93106. Environmental Studies Department, Southern Oregon University, Ashland, Oregon, 97520; Tel/Fax: 541 821-0738; E-mail: dennis@odion.name biodiversity conservation goals. Under the NWFP, ~30% of federal lands traditionally managed for timber production were placed in late-successional reserves that emphasized conservation goals and limited timber harvesting (USFS/USDI 1994). Over the last decade, managers and policy makers have become increasingly concerned about high-severity fire and reduced timber harvesting in NWFP dry forests (e.g., Spies et al. 2006, Power 2006, Thomas et al. 2006, Ager et al. 2007, USFWS 2011). Forest thinning has been viewed as a solution for controlling fires in dry forests throughout western North America (Agee and Skinner 2005, Stephens and Ruth 2005) and commercial criteria have been included to pursue timber harvest goals (Johnson and Franklin 2009, Franklin and Johnson 2012). Commercial thinning prescriptions currently being implemented under these