Wildlife ecologists studying the rare Spotted owl in the forests of California have discovered that large, intense wildfires are not responsible for the breeding territory extinction that has been reported recently.
Instead, the researchers found that post-fire logging operations, which are common on both private and national forest lands, were in fact causing the declines in the territory occupancy of this imperiled wildlife species. In areas, where no logging took place following large forest fires, the scientists failed to detect any significant effect in the spotted owls’ territory occupancy or extinction rate.
“This is good news for declining California spotted owls because this is something that we can control–we can make policy decisions to stop post-fire logging operations in spotted owl habitat,” says Dr. Chad Hanson, a research ecologist with the John Muir Project of the Earth Island Institute and the study’s lead author. His team’s article is published in the open access scientific journal Nature Conservation.
The study sheds light on recent large fires, such as the 99,000-acre King fire from 2014 which affected the Eldorado National Forest in the Sierra Nevada Mountains. As a result, spotted owl occupancy declined in the northern portion of the King fire area. However, the present study finds post-fire logging is to blame.
Post-fire logging removes important spotted owl foraging areas in “snag forest habitats” created by patches of intense fire, explain the scientists. These habitats are rich in small mammal species preyed on by the owls, whereas post-fire logging destroys these habitats, causing higher territory extinction rates.
The study also reports that many of the spotted owl territories in the King fire, which were previously described as lost due to the fire, had in fact already been unoccupied for years before it occurred. Other factors acting before the fire turn out to have been responsible for the occupancy changes at these sites.
The scientists’ findings also help to explain why previous research has found very high spotted owl occupancy in the 257,000-acre Rim fire in the Sierra Nevada prior to post-fire logging, which was then followed by a decline in owl territory occupancy after such logging occurred.
“These results were not surprising considering that spotted owls evolved with forest fires, but logging is a new disturbance to which they are not adapted,” says co-author Monica Bond, a wildlife ecologist with the Wild Nature Institute.
Wildlife researcher and co-author Derek Lee, also affiliated with the Wild Nature Institute, adds, “It is time to stop thinking logging will help the forest; we need to take a much more hands-off approach to forest management, so natural processes can be re-established.”
The study’s results coincide with the strong consensus among hundreds of U.S. scientists opposing post-fire logging operations due to a wide range of ecological harms. Pro-logging members of the U.S. Congress have recently pointed to large forest fires as a justification for proposed logging bills that would override most environmental laws and dramatically increase logging, including post-fire logging, on U.S. National Forests and other public lands.
The results of this study indicate that such legislative proposals would contradict scientific evidence, and harm spotted owls populations. Other studies have also indicated that increased logging would substantially reduce forest carbon storage, and increase greenhouse gas emissions, exacerbating climate change.
Hanson CT, Bond ML, Lee DE (2018) Effects of post-fire logging on California spotted owl occupancy. Nature Conservation 24: 93-105. https://doi.org/10.3897/natureconservation.24.20538
We have nearly completed our owl habitat map for the retrospective analysis. This GIS-based map tracks annual vegetation changes (due to timber harvests, fire, and regeneration) across 74 owl territories from 1993-2012. We expect to finish by the end of January, at which time we can assess the map’s accuracy using "on the ground" data that we collected during the 2012 field season. This map, along with historic owl demographic data, will be used to assess the impact of habitat alteration on spotted owl occupancy, reproduction, and survival.
The data from the 2012 field season has been compiled, entered and validated. On the SNAMP owl study area (Last Chance + Eldorado), the proportion of occupied territories was lower than average (0.45), but reproduction on occupied territories was above average (0.46). The 18 observed nesting attempts produced 16 fledglings.
We are currently preparing for the 2013 field season that begins in April.
The Owl team has a recent publication, you can read about it and find a link to download the article here:
The Owl workplan is available here