October
Big Meadows: Rhythms of Wildfire
I start hiking early in the morning, while the conifers on the slopes above the Green Mountain Trail on the western side of the park remain frosted white from a light snow overnight. Increasing daylight reveals a thicker coat of fresh snow on the highest peaks. Cold breezes hurry me along and there is a look of winter in the gray light smudged beneath the last remaining clouds over the peaks. Soon the sun shines brilliantly on golden aspens running like tongues of fire through the dark green conifers.
October can be a relatively benign month in the park, with clear, warm days between nights when the temperature drops below freezing. Other years, October is the start of winter and quickly moving snowstorms coat the park in white even while the aspens and willows are still dropping their golden leaves. As in the case of September and floods, October is typically not a month prone to wildfires. But human-caused fires have their own seasons and rhythms. Portions of the old-growth forest along the Big Thompson River in Forest Canyon were scorched by a fire started in October 2012 when an illegal campfire near Fern Lake went traveling across the landscape. I think of this as I reach the area known as Big Meadows more than a year after the Big Meadows fire. I vividly remember the start of that fire.
Working in the forest along Glacier Creek the day the fire started, I glanced up at the sky to check whether the summer afternoon thunderheads had begun to coalesce. What looked like a volcanic eruption in progress shocked me to a stop. A thick, dark gray column of smoke rose to the north, apparently just beyond the nearest ridge. The smoke churned like a pot of boiling water, its height and width increasing as I watched. I called to the students I was working with and we speculated about the location of the fire relative to the car and camping gear we had left at the Moraine Park campground that morning. By the time we returned to the campground late in the day, smoke drifting across the continental divide from Big Meadows had settled densely in Forest Canyon and Moraine Park. Our eyes burned and watered and we tried not to breathe too deeply.
Even though the Big Meadows fire has been long extinguished when I hike through the burn area in October, the scent of ash and charred wood lingers in the air. Skeletal trunks remain standing, their blackened surfaces marking my clothes or skin if I carelessly brush against them. Patches of pale, unburned wood glow against the black where foraging woodpeckers have removed the burnt layer. An understory of herbaceous plants sprang up during the past summer, but the ground remains open between the plant stems, with gravel-sized particles still exposed to raindrops and water sheeting down the slopes in the absence of the thick layer of fallen needles that carpets a living forest.
The Big Meadows fire started about 3:30 p.m. on June 6, 2013, with a lightning strike in a grassy area east of Big Meadows. Fires in the national park are not aggressively fought unless they threaten people or infrastructure inside or outside the park, but people in the Colorado Front Range were extremely fire-shy by the summer of 2013, having experienced damaging fires in 2010 and 2012. Firefighters needed more than a week to contain the Big Meadows fire, which burned a little over 650 acres along Tonahutu Creek around Granite Falls.
Even a naturally triggered wildfire typically prompts questions about how long it has been since a fire occurred in the area and how long it will be before the forest recovers. To ask about recovery after a fire is to implicitly regard the fire as an anomaly, a disturbance that ruins a forest and something from which the forest must recover. We could justifiably turn the question on its head and ask how long it will be before fire rejuvenates a forested landscape. The framing of the question reflects our expectations of what is healthy or normal, but the answer to either version of the question is not so easy to determine.
Using annual growth layers in trees to map the age of different patches of forest, ecologists can reconstruct the history of wildfires and the changes in a forest ecosystem following a fire. Before people of European descent settled in the region, ponderosa pine forests between about 6,000 and 7,700 feet in elevation—mostly at the eastern edge of Rocky Mountain National Park and below—burned in low-severity fires at intervals of five to thirty years. These fires mainly burned the ground cover and did not kill mature trees. Started by lightning, these fires were particularly common during dry summers and typically occurred several years after a wetter year that favored the growth of understory plants. Forests of ponderosa pine and Douglas-fir growing between about 8,000 and 9,000 feet in elevation experienced alternating low-severity ground fires and severe, stand-replacing fires at intervals of forty to a hundred years.
At elevations of about 9,300 to 11,000 feet, within the subalpine spruce, fir, and lodgepole pine that form the most common type of forest in the national park, infrequent, high-severity fires started by lightning could kill all of the canopy trees over hundreds to thousands of acres. These fires recurred at intervals greater than a hundred years and commonly at intervals greater than 400 years. As with the fires in lower-elevation forests, these intense fires were triggered by lightning during times of drought.
These return intervals for fires are average values. One of the hallmarks of a natural or unmanaged forest is the diversity of tree ages among different stands of trees. A map of forest stand age for the southeastern portion of the park is like a jigsaw puzzle, with stands of trees less than 100 years old bordering stands more than 400 years in age (see photo 15 in the color insert).
How long it takes a forest to recover following a stand-killing fire depends on how you define recovery. Like a person progressively aging and undergoing different stages of maturity, a forest continues to change through time. Forest ecologists commonly differentiate an early stage during the first 100 years after a fire, when pioneer species such as aspen or lodgepole pine can grow quickly to maturity and create shade that allows seedlings of more shade-tolerant species such as spruce and fir to germinate. The early-stage forest typically has many closely spaced, rather spindly trees: a dog-hair forest. As some of these trees die, the survivors and the shade-tolerant species become more widely spaced and larger in diameter. After 200 years, the forest takes on old-growth characteristics of large, old trees, abundant standing dead trees and fallen trees, and a complex vertical structure of the forest canopy. Even an old-growth forest can continue to change over the next 200 to 300 years, with progressively more downed wood accumulating on the forest floor and progressively larger trees forming the overstory. An intense fire can kill old-growth forest, but this is not necessarily a bad thing if the fire burns only a portion of a very extensive forest.
Fire Ecology
The valley bottom remains relatively wide and the gradient gentle as I turn onto the Tonahutu Creek Trail and continue upstream to Granite Falls. Beyond this the trail steepens as it climbs up toward the alpine zone at Bighorn Flats. I have wandered across the flats in July, admiring the tundra flowers as a large herd of cow and calf elk continually emitted high-pitched cheeps and whistles that I am reluctant to call bugling. But today, as the cold wind reminds me of the coming winter, is not the day for high-elevation adventures. I move beyond the 2013 burn zone into green forest. I understand the importance of wildfires, but I cannot help preferring the sight of green needles and the shelter they provide from the steadily increasing wind.
As with floods, wildfires are natural disturbances that are fundamental to maintaining a healthy forest ecosystem. Nutrients in the ash return to the soil after a fire. Some species of plants require fire to complete their life cycle and some animals rely on these plants. In Rocky Mountain National Park, many lodgepole pines have cones that remain sealed by resin until the heat of a fire melts the resin and releases the seeds. Lodgepole pines do not germinate and grow under the shade of a mature forest canopy, but a fire triggers a new generation of lodgepole seedlings. The seeds of plants as diverse as short-lived wildflowers and long-lived woody shrubs are able to survive the heat of a fire and germinate in large numbers after the fire. As time between fires increases, populations of these species decline and the reservoirs of their seeds stored in the forest soil become depleted. Fire resets the ecological clock of the forest, maintaining forest diversity.
Ponderosa and lodgepole pine forests, in particular, are adapted to fire, but in different ways. Fire kills mature lodgepoles, but also opens the forest canopy and allows the germination of new lodgepole seedlings. In the absence of fire, lodgepoles tend to die out and be gradually replaced by trees such as spruce and fir, which have seedlings that need shade to germinate. Mature ponderosa pines typically survive fires except for intense crown fires. The more frequent ground fires keep the forest floor between the widely spaced mature pines open and sunny, allowing the germination of new ponderosa seedlings.
In addition to benefiting some species of plants, fire creates opportunities for insect-eating birds. Some species forage during the fire on insects flushed by the smoke and heat. Woodpeckers feast on the insects in standing dead trees in the years following the fire. Standing dead trees also create habitat for cavity-nesting birds such as flammulated, northern pygmy, and boreal owls and downy and hairy woodpeckers.
For many years, I imagined woodpeckers as having almost supernatural hearing that allowed them to detect beetles burrowing under the bark of trees. Then one day I happened to be sitting next to a dead tree while doing research in an area blackened by fire the year before. Sunlight reflected from the glossy black surface of the trunk as though the tree was sculpted from obsidian. I heard a crunching noise and looked around for a bird scratching or pecking at the tree. Nothing. Puzzled, I walked around the tree and scanned the surroundings. When I sat down again and listened carefully, it occurred to me that perhaps I was hearing a beetle foraging underneath the charred layer of the tree trunk. A little energetic digging with a pocketknife revealed a small beetle burrowing within the charred wood. The outsized noise made by the little insect reminded me of a night in the desert, sleeping without a tent, when I woke abruptly and hurriedly turned on a flashlight, afraid that a desert bighorn sheep was about to step on my head. A very small toad in the act of crossing my ground tarp blinked confusedly in the blinding spotlight.
As I study the patches of green trees within the burned area of the Big Meadows fire, I am reminded that even large fires typically do not kill all of the forest in an area. A much more common scenario is that a fire will burn a portion of a contiguous forest. This creates opportunities for plants and animals that thrive in the newly exposed area, while other species of plants and animals that thrive in the closed canopy and shaded understory of old-growth forests continue to exist in adjacent, unburned stands.
The healthiest forests are those with the greatest diversity of conditions. These forests support a greater variety of plants and animals and appear to be more resilient to disturbances. An even-aged forest can be highly susceptible to any particular form of die-off, from a beetle outbreak to a blowdown or a wildfire. Just as human societies with people of all ages survived the flu epidemic of 1918 that preferentially killed people in their twenties and thirties, trees of varying ages and varying species differ in their ability to withstand fire, flood, drought, pestilence, and intense winds. A diverse forest is more likely to be only locally affected by whatever challenges are thrown at it.
To Burn or Not to Burn?
Flow in Tonahutu Creek is at its lowest ebb for the year. Patches of bulbous ice edge the water where the creek remains shaded throughout the day. The flowing water creates swiftly flickering patches of light and shadow beneath the ice. Tonahutu is named from an Arapaho word meaning meadow. Bands of Utes lived in what is now the national park, but in 1915 the Colorado Mountain Club convinced the US Geological Survey (which has long been the arbiter of names for natural features because of its role in making topographic maps for the country) to change many of the place names in the park to Arapaho words.
Native Americans in many parts of North America used fire extensively to manage vegetation, drive game animals during hunting, and signal other tribes. The forest cover in much of the continental United States reflected this human-dominated fire regime when Europeans first reached the continent. The Ute and Arapaho tribes using the lands in and around Rocky Mountain National Park at the time of European contact were the latest in a long succession of occupants dating back at least 12,000 years. Low stone walls above timberline in the park appear to have been used by prehistoric Native Americans during game drives. Ancient projectile points have also been found within the park. The projectile points are composed of rock quarried in Middle Park, a broad basin of slightly lower elevation to the west of the national park. Archeologists interpret this to mean that prehistoric occupants of the national park region moved into the area during warmer seasons and spent winters in slightly more hospitable areas. These prehistoric occupants and their historic Native American successors were nomadic hunter-gatherers. There is no evidence that they deliberately set fires within the subalpine or montane forests of the national park region.
The frequency and severity of fires initially increased with European settlement. After trappers removed most of the beavers during the first decades of the nineteenth century, settlement in the Colorado Front Range lagged until the discovery of gold near Denver in 1859. That discovery triggered a series of rushes for gold, silver, and other metals. The sites of mineral discoveries moved back and forth across the mountain range for the next five decades. When a mining strike occurred, several thousand people could rush to what had previously been a largely unoccupied site. These communities had an enormous appetite for wood, which was used in every facet of life—houses, heating, roads, mine construction, railroads, and fuel to power the stamp mills that processed the metals being mined. Deforestation was intense and widespread, assisted by fires started from sparks thrown by railroads, stamp mills, and campfires.
All this removal of trees caused hillslopes to unravel in debris flows, creating so much sedimentation downstream that the farming communities springing up simultaneously at the base of the mountains petitioned Congress to do something. Congress responded with the 1878 Free Timber Act, which made it illegal to harvest live, standing trees on the public domain for commercial purposes. Miners and loggers responded by deliberately setting fires that killed the trees, which could then be legally cut.
Although the region of the national park was largely spared from mining, timber harvest did occur in the park. A sawmill at Hidden Valley supplied lumber for the Stanley Hotel. There was a sawmill along Mill Creek, the Griffith sawmill near Bierstadt Lake, a sawmill at Glen Haven along the North Fork of the Big Thompson River, and two sawmills at Lulu City.
A narrow band of aspens growing up the north-facing slope above Mill Creek forms one of the most visible legacies of these activities. I first noticed the aspens one October, when their golden leaves glowed among the surrounding conifers. A stand of what appear to be individual aspen trees can actually be an enormous single organism connected belowground by roots. Aspens are among the first woody plants to colonize a site newly bared by an avalanche or a flood, yet large aspen colonies can be up to 80,000 years old. I particularly noticed the aspens above Mill Creek because they did not appear to be following the common pattern by growing along the line of a creek. An interpretive sign at the Mill Creek trailhead enlightened me: the aspens mark the location of a tie slide, where cut timbers were trundled down the slope to be collected for transport to a sawmill. Forest succession will eventually replace the aspens with conifers that blend into the surroundings, but for now the aspens form a visual legacy of timber harvest at Mill Creek.
Now there is great reluctance to cut trees in this region, unless the trees are first killed by a natural process such as insect infestation. The change in attitudes toward forests in the Colorado Front Range during the first part of the twentieth century reflects similar changes around the world: once the forests largely disappeared, people realized they had value beyond that of board feet of lumber. Protection started with fire suppression in 1920. By that time, rangers in the national park wanted to protect the scenery that was a key part of visitor experience. National forests outside the park boundaries also experienced rigid fire suppression as part of the new attitude toward protecting forests. Throughout the Front Range and other parts of the western United States, land managers followed the so-called 10 a.m. policy: all fires should be put out by 10 a.m. the morning after they were first spotted. This policy persisted into the late 1970s, long after ecological research had begun to demonstrate the critical importance of periodic fires in maintaining a healthy, diverse forest ecosystem.
Natural resource policy typically lags scientific understanding because policy also reflects societal perceptions. Viewing a charred, smoking, and apparently lifeless landscape after a fire does not readily lead to the understanding that fire is beneficial. And people who build houses in fire-prone areas want nothing to do with wildfires, whether they keep the forest healthy or not.
I turn back at the junction with the trail up to Haynach Lakes. The snow grizzling the conifers earlier in the morning has melted and the air is warm enough for me to start shedding layers of clothing, but these autumn days are short and I want to be back well before dusk. As I descend through the 2013 burn area, I think about how the park service and the public have become more accepting of wildfires.
The 1988 Yellowstone fires were a turning point in societal perception of wildfires in national parks. A series of fires that summer burned 1.2 million acres. The fires were initially portrayed in the news media as a disaster in one of the crown jewels of the national park system. The National Park Service and forest ecologists played a vital role in changing this perception by making the broader public aware of the beneficial aspects of fire. Visiting Yellowstone to watch ecological succession in action became popular in the years following the fire.
Natural resource managers gradually began to practice controlled burns during the 1980s. This involves deliberately setting fires that burn smaller areas with less intensity. These fires are intended to maintain forest health and diversity and to prevent the accumulation of dead plants that can fuel severe fires. Controlled burns remain controversial, however, not least because they can escape control.
Controlled burns, as well as mechanical thinning to reduce potential fuels for wildfire, are now part of the management policy for fires in Rocky Mountain National Park. Because 95 percent of the park is wilderness, however, fires are allowed to burn whenever practical. This can require active public relations as well as fire monitoring and containment, because people accustomed to the dry, windy summers of Colorado are justifiably concerned about the possibility of a fire abruptly “blowing up” beyond the ability of firefighters to contain it. Visitors to the park and residents in the region also dislike the reduced visibility and asthma-inducing smoke associated with fires.
The 1978 fire along Ouzel Creek illustrates one scenario of fires in the park. Triggered by lightning not long after the park service adopted a “let-burn” policy, the fire was monitored but largely left alone, burning over 1,050 acres, until it suddenly sped up and threatened houses outside the park boundaries. At that point, firefighters had to work aggressively to keep the fire within the park boundaries. The 2012 Fern Lake fire, in contrast, spread into the remote, steep terrain of Forest and Spruce Canyons. Partly because the fire did not threaten infrastructure and partly because the area was so difficult to work in, the park conducted a relatively low-level campaign against the fire for about two months until winter snows largely extinguished the flames.
Regrowth in the fire zone near Ouzel Creek, thirty years after the fire.
The Future of Fire in Rocky Mountain National Park
Greater acceptance of wildfires in national parks notwithstanding, people in Colorado remain on edge at the possibility of fire, not least because of the unusually large number of standing dead trees left in the wake of the mountain pine beetle. These beetles feed on ponderosa, lodgepole, and limber pine. The perception is that dead trees equal greater fire hazard, but the reality is not so simple. Trees harboring beetles take some time to die. During the first few weeks of beetle colonization, a fungus carried by the beetle blocks the transport of water and nutrients within the tree, resulting in death. During this phase the needles remain on the tree, but within a year the needles turn orange. This is when the forest is most vulnerable to crown fires, because each dead tree still contains dry, fine fuel in the form of small branches and needles within the canopy. Once the tree has completely died and the needles have fallen off, the dead trees create gaps in the canopy, which limits the intense crown fires that kill living trees and spread rapidly. Scientists have written for several years of how standing dead trees dampen fires, but it is a message that society as a whole is extremely reluctant to accept.
Having gone decades without much timber harvest, Colorado entered a frenzy of tree cutting as beetle-killed forests spread during the first decade of the twenty-first century. Tree cutting in the national park has largely been restricted to corridors of human use—roads, trails, and campgrounds where a falling tree might kill someone. These areas are sometimes known as “sacrifice zones” in which environmentally sound management is set aside in favor of recreation and human safety.
Systematic studies of fire trends across the western United States indicate that fires are becoming more common and widespread. One study found that increases in the number of large fires during 1984 to 2011 were particularly significant in southern and mountainous portions of the West. Another found that large fires became markedly more common in the mid-1980s, particularly in mid-elevation forests of the Northern Rockies, where increasing spring and summer temperatures and an earlier spring snowmelt are efficiently drying the forests. A comparison of temperature, precipitation, and total area burned in the western United States between 1916 and 2003 demonstrated that years with large fires correspond to times of low precipitation, high temperature, and severe drought.
These relationships seem like common sense, but it is sometimes important to rigorously and objectively test common sense, because perceptions can be in error. In this case, statistics support common sense. Climate models suggest that continuing changes in climate and increasing drought severity will facilitate larger and more frequent fires in future. Changes in fire and drought will in turn drive changes in tree ages and the species composition of the forest. My colleague Jason Sibold speculates that the higher-elevation forests of Rocky Mountain National Park will in future resemble the open ponderosa forests of southern Colorado and northern New Mexico.
The future of fire in Rocky Mountain National Park remains an open question. Winters are likely to continue to warm. Combined with decreasing snowpack, this will lead to drier soils and vegetation and increased potential for severe fires. As humans encroach on the park boundaries from all sides, there will be more pressure on the park service to suppress and contain fires both because of their potential to spread outside the park boundaries and because of the air pollution widespread fires produce.
Long Live Wet Meadows
As I come back into Big Meadows I inadvertently flush a herd of elk out of the trees and into the meadow. I feel the damp ground shake with the force of their hooves. The sounds of their movement among the grasses resemble a strong wind approaching through a forest. I think of the Utes and Arapahos who depended on elk such as these for meat and how the name of Tonahutu reflects the importance of the extensive meadows. A meadow represents a place where trees cannot grow, either because the soil is too wet or because fire has at least temporarily removed the trees. Despite the absence of contemporary beavers, Big Meadows remains a beaver meadow and marsh area that is too wet for trees. Although such areas can burn, they are less likely to do so than the adjacent upland forest.
Past generations of beavers in Big Meadows built dams that blocked flow and caused channels to branch across the broad valley bottom before rejoining downstream. From the air, the active and abandoned channels resemble the tracks left by skiers slaloming down a slope. The low-angle autumn sunlight highlights subtle differences in vegetation and topography along the complicated turns and loops left by Tonahutu Creek, as well as the straighter lines of elk and moose trails that cross the meadows.
River scientists sometimes use a “string of beads” approach to restoring and managing rivers. Beads are the portions of the river where restoration is more feasible—national wildlife refuges along the Mississippi River, for example, that preserve broader floodplains and provide an opportunity to manage floodplain wetlands. The string is the narrow, simpler portion of river between each bead, where dredging, levee construction, and agriculture or urbanization limit the ability to re-create natural river processes such as periodic flooding. Restoring the entire length of a river may be neither feasible nor necessary to restore river processes that maintain diverse plant and animal communities: some ecological form and function can be restored by focusing mostly on the beads.
Mountain streams are also beaded as a result of natural processes. The rivers of Rocky Mountain National Park are mostly composed of strings—the steep, narrow portions in which water, sediment, and nutrients move along at a brisk pace and the valley bottom is barely wider than the creek. Between these strings are the beads of wider, gentler valley segments in which logjams and beaver dams help to create and maintain a broader floodplain and secondary channels.
Beads, whether enamel, glass, or gems, are the main attraction on a beaded piece of jewelry or clothing. Beads are also the main attraction in a river network, creating abundant habitat that supports diverse species of plants and animals, and storing nutrients and water to create a productive environment that fosters greater numbers of individual organisms. To completely mix metaphors in a chapter focused on wildfire, river beads are the biogeochemical and biodiversity hot spots within the greater landscape.
Moose graze in Big Meadows before the 2013 fire.
I grew up near Cleveland, Ohio, where the parks ringing the metropolitan area are known as the emerald necklace. The name aptly describes beaver meadows, which appear as brighter, lighter green beads on the river-strings of the Southern Rockies. Restoring or maintaining these beads affects the greater landscape. The riverine beads buffer the uplands and other portions of the river network against the extremes and create environments where unique communities of water-loving plants and animals thrive in the dry climate of the Southern Rockies. In particular, the wet meadows maintained by beavers help to buffer the larger landscape from the effects of fires, creating natural fire breaks that also help to maintain forest diversity. Beaver meadows also buffer rivers against floods, and the meadows can buffer rivers against droughts, as water stored in the subsurface helps to maintain surface flow when winter snows and summer rains fail. As I hike back down through Big Meadows, I think about how we will need these meadows—and the beavers that maintain them—more than ever in a warmer, drier future.