Rockweit, J. T., A. B. Franklin, and P. C. Carlson. 2017. Differential impacts of wildfire on the population dynamics of an old-forest species. Ecology 98:1574-1582.
Don’t Yell “Fire!”
Wildfire can be a word that strikes unease or fear into those who hear it. Many people are afraid of wildfires, but they are actually essential events to how ecosystems function and are shaped. In a changing world, wildfire events themselves are changing and having an even larger impact on how they alter the environment. When an environment is changed, the animals that use that environment are also greatly changed. From the smallest ant to the largest bear, everything that lives in a forest community feel the impacts of a wildfire. In the Pacific Northwest where these types of environmental alterations are frequent, a group of researchers set out to investigate how one specific species, the northern spotted owl (Strix occidentalis caurina), is impacted by the change in wildfire patterns and intensity.
Who, Where, and What
Due to these changes in ecological disturbances from fire, one group of researchers decided to take a closer look at this system in the Pacific Northwest. In the Klamath Ecological Province, located in northwestern California and southwestern Oregon, lies a biodiversity hotspot. Hot spots are known for their high diversity in the types of animals and plants living in an area, and researchers here are looking at this rich diversity in a mixed hardwood-conifer forest.
Within this mixed forest one species stands out among the rest: the northern spotted owl. The northern spotted owl is a threatened species and is researched mostly because of this status. Mostly considered to rely solely on old-growth forests, in this region the northern spotted owl has the potential to thrive off of areas with mixed aged forest. A mixed age forest allows for more diversity among the species that live there. More diversity would mean these owls have a higher chance of finding prey to survive.
The continual change in forest fire patterns throughout the Klamath region results in various forest types and stages. Past research, however, has pointed to these wildfire disturbance regimes as having mixed effects on the northern spotted owl. With such clashing views on how the northern spotted owl is affected by wildfire, researchers decided to try and settle the differences of this system.
Putting the ‘Fire’ Out
Two of the main pieces that researchers wanted to get to the bottom of were owl survival (how many lived through wildfire events) and recruitment (how many owls were producing young after the event and reusing the burned area). Through observations in the forest and estimating northern spotted owl survival and recruitment researchers found a trend that in severe fires many owls perished, but the ones that survived produced more young. In a low impact fire, on the other hand, the owls were not affected. A higher production of young means there are more mouths to feed and while owls may not be able to inhabit severely burned areas, these burned habitats do make for better hunting grounds. With more ease of hunting food, owls are more likely to sustain larger amounts of young.
Wildfires continue to change the composition of forest communities and in time will likely have larger impacts than ever. This change is worth studying and the researchers of Colorado State University and the National Wildlife Research Center were able to gather valuable information about one species that relies on the forest being affected by the changes in wildfire patterns. Overall it was found that having a mixed forest was best for northern spotted owls, as open burned areas gave way to easier hunting grounds, while old growth areas were better habitat. Having insight to how one species will react to more intense and larger forest fires may be helpful; through means of surveying and estimation methods or as a model on how other species will react. Studying wildfire patterns and the impact on forest communities, especially old-growth forests, is critical as time goes on and the Pacific Northwest are predicted to become hotter, drier, and longer.