By Betsy L. Howell
ONE IS A BIRD OF PREY that lives in the old-growth, coniferous forests of western North America; the other is a terrestrial amphibian restricted to a single mountain range in New Mexico. One can fly great distances across the landscape in search of food, mates and better living conditions; the other stays mostly underground and may not travel more than a few feet in its lifetime. For all their differences, both the California spotted owl (Strix occidentalis occidentalis) and the Jemez Mountains salamander (Plethodon neomexicanus) are experiencing similar alterations to their respective habitats. One of these significant change agents is wildfire.
Large wildfires in the western United States have dominated most summer news cycles. Each season, records are broken for largest fires, most erratic fire behavior and total economic costs. The effects on human communities are varied, depending on where people live and how they make a living. The same is true for wildlife species residing in forests affected by fires. As today’s land managers and biologists deal with the consequences of a century of fire suppression, a changing climate and insect outbreaks, the question is, will species adapt?
Gavin Jones, a Ph.D. candidate and researcher at the University of Wisconsin at Madison, has been examining the effects of disturbance on California spotted owls. More than three years ago, an opportunity from a human-caused fire presented itself to look at how wildfires, particularly high-severity, stand-replacing fires, might affect the owls.
“The 2014 King Fire in the Sierra Nevada gave us a natural experiment,” Jones says. “This fire burned through parts of the Eldorado demography study area where we had 20 years of data on spotted owls.”
Birds individually marked with leg bands and GPS backpacks had been helping researchers understand their movements, breeding success and habitat use, and the fire, a 97,000-acre blaze that included a mix of high- and low-severity impacts across the landscape, allowed Jones and his colleagues to see how the birds responded. The owls’ behavior, they found, very much depended on what the fire did to the forest.
“When more than half of a spotted owl’s territory burned at high severity, we observed those sites becoming unoccupied,” Jones explains. “But in other parts of the fire area, where territories were less extensively affected by severe fire, the owls remained. The same held true for places of low- and moderate-severity fire impacts. We observed several instances of post-fire breeding dispersal by birds from the most severely-burned stands, which is a relatively rare behavior in the species. However, we also witnessed owls using severely burned areas, but generally only when the patches of affected forest were smaller.”
Ray Davis, with the U.S. Forest Service in Corvallis, Ore., agrees about the size of areas owls will use after a fire. Davis, who is the monitoring lead for older forests and northern spotted owls (S. o. caurina), the subspecies of spotted owl that lives north of the California birds, says: “Small patches of severely burned forest in territories that have adequate nesting and roosting forest cover may actually be beneficial in terms of improving conditions for prey populations.”
Research by Jeremy Rockweit, Alan Franklin and Peter Carlson, published in Ecology in 2017, looked at long-term demographic data of northern spotted owls and effects from fires. Their work showed reduced survival of adult owls and increased recruitment of other spotted owls in territories that experienced moderate- to high-severity fire. Unfortunately, the immigrants also appeared to experience lower survival in these areas, which may effectively be functioning as population sinks, or areas where death rates exceed birth and immigration rates.
In the Eldorado study area, some birds disappeared after the fire, so their fates are not known. One owl, recovered by Jones’ colleagues, died directly from the fire, possibly from smoke inhalation. Even having tremendous mobility compared to other wildlife species does not insulate individuals from the potentially fatal impacts of fast-moving, unpredictable fires. Still, an owl’s ability to fly provides options not available to other species, including many amphibians.
The Jemez Mountains salamander is a terrestrial, lungless salamander that breathes through its skin. It requires moisture to breathe, but does not need standing or moving bodies of water to complete its life cycle. This salamander emerges from its life underground during the monsoon season to breed and forage. It then returns to its subterranean world to lay eggs that hatch into smaller versions of itself, rather than larval forms that later develop into adults. Because Jemez Mountains salamanders live mostly beneath the forest floor, they are difficult to find. Samantha Cordova did her graduate work at the University of New Mexico on the state’s endemic salamanders, including the Jemez Mountains salamander, and acknowledges the challenges.
“We do presence-absence surveys,” Cordova says, “but an absence during surveys could indicate suboptimal conditions rather than true absence. With this survey method, it is difficult to say if Jemez Mountains salamanders are absent, how many there are, and how they have responded to a wildfire.”
The range of the Jemez Mountains salamander includes approximately 375 square miles of high-elevation habitats on the rim and resurgent domes of the Valles Caldera in the Jemez Mountains. Several large fires, including the 2000 Cerro Grande Fire, the 2012 Las Conchas Fire, the 2016 Thompson Ridge Fire, and the Cajete Fire in 2017, have burned through the salamander’s habitat.
“We do find Jemez Mountains salamanders in mosaic burns like the Thompson Ridge Fire,” Cordova says, “but I have not spent enough time searching in severely burned areas of the Las Conchas Fire because the sporadic monsoon season dictates when and where to survey. Salamanders have lived in the Jemez Mountains for millions of years, and based on fire ecology work by Ellis Margolis, we assume they persisted through frequent, low-intensity fires. So, the question of how they respond to high-intensity fires still remains.”
Back in the Pacific Northwest, the 2017 Eagle Creek Fire in the Columbia River Gorge between Washington and Oregon may help provide some answers on fire impacts to terrestrial salamanders. The 49,000-acre fire burned through 15 documented locations of the Larch Mountain salamander (Plethodon larselli), a species closely related to the Jemez Mountains salamander with a similar narrow range. Larch Mountain salamanders occur in steep, forested talus slopes and lava tube entrances along a 36-mile stretch of the Columbia River Gorge, as well as an approximately 120-mile area of the Cascade Range north of the gorge. Dede Olson, a research ecologist with the U.S. Forest Service Pacific Northwest Research Station in Corvallis, Ore., says the Eagle Creek Fire, like the California King Fire in 2014, presents a research opportunity.
“Minimally, we hope to go back to known sites and look for occupancy,” Olson says. “If enough sites were in and out of fire-affected areas in comparable habitat conditions, we may be able to do an experimental design of burned and unburned sites to look at effects on abundance without pre-treatment data. If a good design is not possible and if some affected sites had information from earlier surveys work, we can try to conduct abundance assessments for comparison on a per-site basis.”
While recent western wildfire events potentially provide circumstances to assess the effects of fire on different wildlife species, as well as opportunities to develop survey methods to understand those effects, the costs may outweigh the benefits. Only time will tell if animals such as spotted owls and lungless salamanders can adapt fast enough to survive in the habitats that remain.
Betsy L. Howell is a writer living on Washington’s Olympic Peninsula.