Colorado's Front Range fire severity not much different than past

A new study indicates present-day forest fires on Colorado's Front Range are not significantly more intense than historical fires. Credit: Glenn Asakawa, University of Colorado

The perception that Colorado's Front Range wildfires are becoming increasingly severe does not hold much water scientifically, according to a massive new study led by the University of Colorado Boulder and Humboldt State University in Arcata, Calif.

The study authors, who looked at 1.3 million acres of ponderosa pine and mixed conifer forest from Teller County west of Colorado Springs through Larimer County west and north of Fort Collins, reconstructed the timing and severity of past fires using fire-scarred trees and tree-ring data going back to the 1600s. Only 16 percent of the study area showed a shift from historically low-severity fires to severe, potential crown fires that can jump from treetop to treetop.

The idea that modern fires are larger and more severe as a result of fire suppression that allowed forest fuels to build up in the past century is still prevalent among some, said CU-Boulder geography Professor Thomas Veblen, a study co-author. "The key point here is that modern fires in these Front Range forests are not radically different from the fire severity of the region prior to any effects of fire suppression," he said.

A paper on the subject was published Sept. 24 in the journal PLOS ONE. The study was led by Associate Professor Rosemary Sherriff of Humboldt State University and involved Research Scientist Tania Schoennagel of CU-Boulder's Institute of Arctic and Alpine Research, CU-Boulder doctoral student Meredith Gartner and Associate Professor Rutherford Platt of Gettysburg College in Gettysburg, Pa.

The study was funded by the National Science Foundation.

"The common assumption is that fires are now more severe and are killing higher percentages of trees," said Sherriff, who completed her doctorate at CU-Boulder under Veblen in 2004. "Our results show that this is not the case on the Front Range except for the lowest elevation forests and woodlands."

One important new finding comes from a comparison of nine large fires that have occurred on the Front Range since 2000 -- including the 2002 Hayman Fire southwest of Denver, the 2010 Fourmile Canyon Fire west of Boulder and the 2012 High Park Fire west of Fort Collins -- with historic fire effects in the region.

"It's true that the Colorado Front Range has experienced a number of large fires recently," said Schoennagel. "While more area has burned recently compared to prior decades -- with more homes coming into the line of fire -- the severity of recent fires is not unprecedented when we look at fire records going back before the 1900s."

In addition, tree-ring evidence from the new study shows there were several years on the Front Range since the 1650s when there were very large, severe fires. The authors looked at more than 1,200 fire-scarred tree samples and nearly 8,000 samples of tree ages at 232 forest sample sites from Teller County to Larimer County.

The study is one of the largest of its kind ever undertaken in the western United States. The team was especially interested in fire records before about 1920, when effective fire suppression in the West began in earnest.

"In relatively dry ponderosa pine forests of the West, a common assumption is that fires were relatively frequent and of low severity, and not lethal to most large trees, prior to fuel build-up in the 20th century," said Veblen. "But our study results showed that about 70 percent of the forest study area experienced a combination of moderate and high-severity fires in which large percentages of the mature trees were killed."

Along the Front Range, especially at higher elevations, homeowners and fire managers should expect a number of high-severity fires unrelated to any kind of fire suppression and fuel build-up, said Schoennagel. "This matters because high-severity fires are dangerous to people, kill more trees and are trickier and more expensive to suppress."

"Severe fires are not new to most forests in this region," said Sherriff. "What is new is the expanded wildland-urban interface hazard to people and property and the high cost of suppressing fires for society."

In addition, a warming Colorado climate -- 2 degrees Fahrenheit since 1977 -- has become a wild card regarding future Front Range fires, according to the team. While fires are dependent on ignition sources and can be dramatically influenced by high winds, the team expects to see a substantial increase in Front Range fire activity in the low and mid-elevations in the coming years as temperatures continue to warm, a result of rising greenhouses gases in Earth's atmosphere.

Source: University of Colorado at Boulder

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Coexist or perish, new wildfire analysis says: Changing wildfire paradigm from fighting to coexistence

The lightning-sparked Castle Rock Fire burned nearly 50,000 acres in 2007 in the Sawtooth National Forest and adjacent state and private lands surrounding Ketchum, Idaho, in the Smoky Mountains region of the Rocky Mountain range. Credit: Kari Geer, courtesy of the National Interagency Fire Center

Many fire scientists have tried to get Smokey the Bear to hang up his "prevention" motto in favor of tools like thinning and prescribed burns, which can manage the severity of wildfires while allowing them to play their natural role in certain ecosystems.

But a new international research review led by the University of California, Berkeley, says the debate over fuel-reduction techniques is only a small part of a much larger fire problem that will make society increasingly vulnerable to catastrophic losses unless it changes its fundamental approach from fighting fire to coexisting with fire as a natural process.

The paper, "Learning to Coexist with Wildfire," to be published in the Nov. 6 issue of the journal Nature, examines research findings from three continents and from both the natural and social sciences. The authors conclude that government-sponsored firefighting and land-use policies actually encourage development on inherently hazardous landscapes, amplifying human losses over time.

"We don't try to 'fight' earthquakes -- we anticipate them in the way we plan communities, build buildings and prepare for emergencies. We don't think that way about fire, but our review indicates that we should," said lead author Max Moritz, Cooperative Extension specialist in fire at UC Berkeley's College of Natural Resources. "Human losses will only be mitigated when land-use planning takes fire hazards into account in the same manner as other natural hazards, like floods, hurricanes and earthquakes."

The analysis looked at different kinds of natural fires, what drives them in various ecosystems, the ways public response to fire can differ, and the critical interface zones between built communities and natural landscapes. The authors found infinite variations on how these factors can come together.

"It quickly became clear that generic one-size-fits-all solutions to wildfire problems do not exist," Moritz said. "Fuel reduction may be a useful strategy for specific places, like California's dry conifer forests, but when we zoomed out and looked at fire-prone regions throughout the Western United States, Australia and the Mediterranean Basin, we realized that over vast parts of the world, a much more nuanced strategy of planning for coexistence with fire is needed."

Planning for co-existence

If humans choose to live in fire-prone regions, fire must be managed on par with other naturally occurring hazards, the authors argue, and research must seek to understand what factors and outcomes we can and cannot affect.

One common tool is applicable to the vast array of ecological and social science interactions at the critical wildfire/urban interface: more effective land-use planning, along with the regulations that guide it.

The authors recommend prioritizing location-specific approaches to improve development and safety in fire-prone areas, including:

Adopting new land-use regulations and zoning guidelines that restrict development in the most fire-prone areas;

Updating building codes, such as requiring fire-resistant construction to match local hazard levels and encouraging retrofits to existing ignition-prone homes;

Implementing locally appropriate vegetation management strategies around structures and neighborhoods;

Evaluating evacuation planning and warning systems, including understanding situations in which mandatory evacuations are or are not effective;

Developing household and community plans for how to survive stay-and-defend situations; and

Developing better maps of fire hazards, ecosystem services and climate change effects to assess trade-offs between development and hazard.

As an example of positive steps, the report cites new fire danger mapping efforts, including an existing fire hazard severity zone map that guides building codes in California. Produced by the state's Department of Forestry and Fire Protection, the current map does not explicitly incorporate locally varying wind patterns, which influence the worst fire-related losses of homes and lives, but future iterations will include these data.

Fire ecology and climate

The authors underscore that wildfires are a natural part of many ecosystems and can have a positive long-term influence on the landscape, despite people labeling them as "disasters." They can stimulate vegetation regeneration, promote a diversity of vegetation types, provide habitat for many species and sustain other ecosystem services, such as nutrient cycling.

Around the world, the numbers, sizes, and intensities of fires vary greatly. In some ecosystems, big, severe wildfires are natural events and more climate-driven -- by drought or high winds -- so fuel reduction is not a very effective tool in these locations. By contrast, many ecosystems that would naturally experience frequent lower-severity fires may respond to vegetation management aimed at both reducing fire hazard to humans and restoring crucial ecosystem processes. But, the authors agree, where fuel reduction is an appropriate goal, it would ideally be achieved by letting wildfires do their job.

A changing climate will complicate management strategies.

"How should future fire patterns compare to this historical variability? That's the big question," Moritz said.

Describing wildfire as "one of the most basic and ongoing natural processes on Earth," the authors call for a paradigm shift in the way society interacts with it, changing to an approach that achieves long-term, sustainable coexistence that benefits the planet's ecosystems on the landscape scale, while minimizing catastrophic losses on the human scale.

"A different view of wildfire is urgently needed," said Moritz. "We must accept wildfire as a crucial and inevitable natural process on many landscapes. There is no alternative. The path we are on will lead to a deepening of our fire-related problems worldwide, which will only become worse as the climate changes."

Source: University of California - Berkeley

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Even in restored forests, extreme weather strongly influences wildfire's impacts

Fire Sweeps Up, South Flank, Rim Fire. Credit: Mike McMillan - USFS

The 2013 Rim Fire, the largest wildland fire ever recorded in the Sierra Nevada region, is still fresh in the minds of Californians, as is the urgent need to bring forests back to a more resilient condition. Land managers are using fire as a tool to mimic past fire conditions, restore fire-dependent forests, and reduce fuels in an effort to lessen the potential for large, high-intensity fires, like the Rim Fire. A study led by the U.S. Forest Service's Pacific Southwest Research Station (PSW) and recently published in the journal Forest Ecology and Management examined how the Rim Fire burned through forests with restored fire regimes in Yosemite National Park to determine whether they were as resistant to high-severity fire as many scientists and land managers expected.

Since the late 1960s, land managers in Yosemite National Park have used prescribed fire and let lower intensity wildland fires burn in an attempt to bring back historical fire regimes after decades of fire suppression. For this study, researchers seized a unique opportunity to study data on forest structure and fuels collected in 2009 and 2010 in Yosemite's old-growth, mixed-conifer forests that had previously burned at low to moderate severity. Using post-Rim Fire data and imagery, researchers found that areas burned on days the Rim Fire was dominated by a large pyro-convective plume -- a powerful column of smoke, gases, ash, and other debris -- burned at moderate to high severity regardless of the number of prior fires, topography, or forest conditions.

"The specific conditions leading to large plume formation are unknown, but what is clear from many observations is that these plumes are associated with extreme burning conditions," says Jamie Lydersen, PSW biological science technician and the study's lead author. "Plumes often form when atmospheric conditions are unstable, and result in erratic fire behavior driven by its own local effect on surface wind and temperatures that override the influence of more generalized climate factors measured at nearby weather stations."

When the extreme conditions caused by these plumes subsided during the Rim Fire, other factors influenced burn severity. "There was a strong influence of elapsed time since the last burn, where forests that experienced fire within the last 14 years burned mainly at low severity in the Rim Fire. Lower elevation areas and those with greater shrub cover tended to burn at higher severity," says Lydersen.

When driven by extreme weather, which often coincides with wildfires that escape initial containment efforts, fires can severely burn large swaths of forest regardless of ownership and fire history. These fires may only be controlled if more forests across the landscape have been managed for fuel reduction to allow early stage suppression before weather- and fuels-driven fire intensity makes containment impossible. Coordination of fire management activities by land management agencies across jurisdictions could favor burning under more moderate weather conditions when wildfires start and reduce the occurrences of harmful, high-intensity fires.

Source: USDA Forest Service - Pacific Southwest Research Station

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