Oregon State University College of Forestry’s Dr. Garrett Meigs is a self-professed Beaver Pyromaniac. That’s the name that he and his OSU research group have coined for themselves. Meigs and his colleagues study forest fires, especially those in the Pacific Northwest. Friday night he brought two new, and very hot topics in forest fire science research to Wallowa County via a talk at Wallowology.
The first: The distribution and importance of fire refugia—areas of low severity burns which serve as sanctuaries for fire-intolerant species, allowing those plants to quickly repopulate the more intensely burned landscape.
The second: His findings that forests which include large swaths of insect-killed trees can be actually less likely to burn than equivalent forests that have minimal insect-driven mortality. And that when they do burn, the insect-killed areas burn with less severity than the equivalent live forest.
“The concept of forest health is in the eye of the beholder,” Meigs said. “Insects and fire are just processes of change, and they are part of a forest’s normal disturbance ecology. Insect outbreaks with native insects (mountain pine beetle and western spruce budworm) can erupt into an epidemic. But we’ve found that even major outbreaks of insects don’t increase fire severity or fire likelihood.”
“Certainly there are big fire events where there have been insect outbreaks,” he said.
“But our studies show that for mountain pine beetle outbreaks, fires are less severe and it’s a toss-up whether there is a greater or lower fire probability. For western spruce budworm outbreaks, we actually found both a lower likelihood of fire, and lower severity when fires occurred.”
So maybe there’s something more cost effective than controlling insect outbreaks we can do, Meigs suggested — protecting communities, and restoring ecosystems. “The insects alone are not the top problem,” he said.
We all know that forest fires can be devastating. But even the most severe leave behind patches that somehow escape the flames. These areas are known as fire refugia. Some are unburned. Some have experienced low-intensity fire amid what was a conflagration elsewhere in the same burn. Meigs has found that on average, forest fires across the Pacific Northwest leave about 38 percent of their area relatively unscathed, providing critical sources of local seeds to revegetate the landscape, and habitat for animal repopulation. These areas comprise fire refugia.
Wikipedia defines refugia as “locations that support an isolated or relict population of a once more widespread species. This isolation can be due to climatic changes, geography, or human activities such as deforestation and overhunting.” For listed salmon, refugia might be a shaded, cold-water stream. During the Ice Age, refugia were places where animals retreated from ice, snow and chilling climates to survive, and then re-expand into their former habitats (or what was left of them) once the ice retreated and the climate warmed. Those included the black-footed ferret, which found refuge in the Columbia basin, the northern flying squirrel, and the black bear, along with many other grassland and temperate forest species. As ice sheets melted and ecosystems became more temperate, species that had been confined to milder, ice-free habitat expanded back into their former ranges.
Fire refugia are locations disturbed less frequently or less severely by wildfire relative to the surrounding vegetation and landscape. They are sanctuaries--places where the dominant vegetation survives, along with many fire sensitive creatures from butterflies to squirrels, which will venture into the more severely burned places to repopulated those places with local seeds and animals.
Meigs got interested in fire and fire refugia while an undergraduate, studying goshawks and their habitat in fire-prone northern Arizona. For his most recent study he collaborated with OSU colleague Dr. Meg Krawchuk, to examine the prevalence of refugia in almost 100 fires that burned about 2,400 square miles of eastside Pacific Northwest forests in the decade between 2004 and 2015. Those fires included three fires in the southeast Wallowas, two in Hells Canyon, the 2015 Grizzly Complex in northern Wallowa County and the 2015 Canyon Creek Complex in Grant County. Meigs and Krawchuck used Landsat satellite images to measure the extent of fires, burned and unburned areas, and evaluate the pre-burn landscape.
They found that the amount of land spared from fire within the burned zone varied with the type of forest. In juniper woodlands, about 70% of the forest burned at low severity. In subalpine forests, only about 28% of the area escaped flames. Other forest types, including mixed conifer and Ponderosa pine (the most common in Wallowa County), were in-between at about 34% of their areas left as refugia.
But, Meigs noted, the structure of the forest also has a big effect on the amount of area left as refugia. The presence of large trees and/or open space in the forest proved important in retaining unburned or low-intensity-burned refugia areas. Where forests had very open canopies, or were dominated by large trees (greater than 21” in diameter) an average of 55 percent of the fire’s total area was low severity or unburned, and would be refugia. But in forests dominated by small trees, only 23 percent of the area burned at low severity or remained unburned, providing refugia for plants and animals.
Exactly which areas are left as refugia depends upon multiple factors, including fire weather, fuel conditions, and fire fighting efforts. Places protected by backfires, plowed or cut perimeters, roads, or aerial drops of water or borate, are less likely to burn severely and may serve as refugia. But there are other factors too, many of them natural or endemic conditions.
Meigs and Krawchuk’s eventual goal is predicting which places in a forest are most likely to become refugia. They are finding that topography may be a factor. Some refugia are found in moister places, others in open spaces like meadows. Having used Landsat imagery to define the locations, the next step is to deduce why these areas were spared, and whether they are what are known as “persistent” refugia—places where fire severity has been low over multiple fire cycles.
The science may eventually be able to provide models to help with management,. “But the best management will vary with each locale, and the kind of management required,” Meigs said.
To the public and to some forest managers, Meigs noted, the principal threats to forests and forest ecosystems seem to be fire, defoliators, pathogens and bark beetles. But to the forest itself, the greater threats come from climate change, introduced species, and the demands for resources and space from an increasing human population.
“How we think about forest health in an era of rapid global change is important,” he said. This is all happening when things are changing in unprecedented and unpredictable ways.”