Yellowstone Rises from the Ashes
by Professor of Biology David Krohne
I watched those TV images with growing fascination. I admit that I did not watch the television footage of the fires with the same horror that many people did. It was clear that we were witnessing a significant and fascinating ecological event--one similar in magnitude and importance to the eruption of Mt. St. Helens in 1980. The fact that it was occurring in the world's first national park added to my interest. Not only did the fires raise basic ecological questions, they had important management implications as well.
In August of 1989, I made the first of several visits to Yellowstone to see firsthand the effects of the fires and the nature of the recovery that was just beginning. It seemed an ideal opportunity to begin a long-term photographic documentation of the recovery of the landscape--one that might be useful in my ecology class and a freshman tutorial on land management and conservation I was planning to offer. And it provided an excuse to spend time in one of my favorite parts of the West!
"Not a Living Thing Remained"
On that first visit I entered the park from the east entrance. I kept waiting to see the miles of blackened forest I expected from the television reports. Instead I drove through miles of unburned forest and meadow. It wasn't until I neared Yellowstone Lake that I encountered the first of the large burns. By then it was clear that although one-third of the park had burned, the rest of it--nearly 1.5 million acres--was green, lush, and extensive.
Yet in a few sites, particularly near the Norris Geyser Basin, the devastation was stunning. One spot on the road between Norris Junction and the Canyon area was especially striking. I arrived at this site the first time at dusk. It sits on a small hill and so the view drops away in all directions. Not a living thing remained on the site--no flowers had germinated, no tree seedlings were evident--nothing. Each step on the blackened ground raised small clouds of dust and ash.
I learned over the next few days that such sites were the exception rather than the rule. I was struck by the variation in fire intensity experienced at different sites. The landscape was a mosaic of unburned, lightly burned, and heavily burned patches. Many hillsides had "bullseye" patterns--hot intense fires in the center of a patch, a ring of burned but surviving trees, and finally another ring of mild, partial burn surrounding it all.
What will be the long-term effects of the fires? And what are the management implications of this event? A brief outline of the fire ecology and history of the Yellowstone region allows us to address these questions.
A Forest Ripe for Fire
The development of a community after a disturbance is a process called succession. Thanks to some detailed studies of Yellowstone by W.H. Romme and D.G. Despain of Montana State University, we know quite a lot about this process in Yellowstone. Much of the Yellowstone area is lodgepole pine forest. After a fire, lodgepole pines germinate in large numbers because heat causes the trees' cones to open and release the seeds. In the years immediately after fire, dense stands of lodgepole pines develop. These stands are relatively non-flammable--there is little fuel on the ground and the trees are green from top to bottom, making it difficult for fire to reach the canopy.
As the forest develops and the trees mature and die, more fuel is available on the forest floor and dead branches can conduct fire into the canopy. Pine bark beetles infest and kill older trees, substantially adding to the accumulated fuel. Two-hundred to 300 years after a fire, the community is ripe for another fire. From cores taken from older trees, one can determine the fire history of the region by looking for fire scars among the growth rings.
Romme and Despain have found evidence of a large-scale fire in the Yellowstone region approximately 300 years ago. So by 1988 much of the area was in the final stage of succession and highly vulnerable to fire.
The summer of 1988 was unusual. A wet spring was followed by one of the driest summers on record. A series of dry storms from the south brought strong, desiccating winds that reduced the moisture content in wood on the ground from a normal 17% to less than 5%. These storms were accompanied by intense lightning--for example, on July 17 more than 2,000 lightning strikes to the ground were recorded. The result was a steady progression of fires culminating in so-called Black Saturday (August 20) when 165,000 acres burned in a single day--more than had burned in any decade since 1872!
Political Firestorm in Washington
As the fires grew in intensity, the National Park Service came under great criticism for its "let-burn policy" in the park. This policy recognized fire as a natural and important factor in conifer forests. According to the policy, any fire caused by lightning was allowed to burn unless it threatened people or property. All fires caused by humans and thus defined as unnatural, were to be put out immediately. In effect, this policy had relatively little to do with the development of the fires that summer. Two of the major fires were started by humans and attempts were made to extinguish them from the outset. Considering the stage of succession in most of the park and the unusual climatic conditions, these efforts were futile. A major fire was nearly inevitable.
It is also unlikely that the previous Park Service policy of total fire suppression earlier in this century, before the "let-burn policy" was adopted, allowed sufficient fuel to build up to the point that a major conflagration resulted. Much of the Yellowstone backcountry is rather inaccessible, so efforts to suppress fires were relatively unsuccessful until aircraft were introduced following World War II. The forty-year period of fire suppression before 1988 was insufficient to allow large amounts of fuel to accumulate.
An Emerging Beauty
I have returned to Yellowstone every two years since 1989. For an ecologist, the opportunity to observe the subtle differences among sites in the pattern and timing of recovery has been fascinating. But equally striking has been the emerging and changing beauty of the burned landscapes. In the first two years after the fire, many of the hottest burns were transformed into a sea of pink fireweed, a beautiful plant especially adapted to colonize burned forests. Other sites developed miniature lodgepole pine forests with phenomenal tree densities. The park service has counted up to one million lodgepole pine seeds per acre in some areas.
The effect on the wildlife has been no less significant. In 1991 I watched moose, normally inhabitants of low, boggy habitats, foraging on fireweed as high as 9,000 feet on the side of Mt. Washburn, far above their normal habitat. Some of the cooler burns support tremendous stands of grass. For the elk, it is like living in a grocery store. Each of these sites is criss-crossed with elk trails. If you want to see elk--go to the burns. Until the fires, I'd never seen so many cows with twin calves--a phenomenon that raises serious questions about future herd management.
For me, one of the most interesting aspects of the fires has been the way they have forced us to think carefully about how we perceive and manage our parks and natural areas. We preserved Yellowstone for two reasons: to safeguard a landscape we find aesthetically appealing, and to maintain a place where natural processes can take place. People found the miles of late succession lodgepole pine forests beautiful. Indeed, the pre-fire Yellowstone landscape was an idyllic, lush forest. But we also wanted a park where nature could take its course, where human impact is minimal. We have learned that these goals may be contradictory. A natural area is not a fixed and permanent entity. The scientific data show us that the Yellowstone landscape is dynamic--perhaps on a long time scale--but dynamic nevertheless. How do we preserve a beautiful but ephemeral moment in succession?
My own bias is to preserve the natural process. In part this is due to my intellectual interest in the succession process. Yellowstone will yield important scientific information about succession in the years to come. But beyond that, I also find the post-1988 landscape more visually appealing as well. The miles of green lodgepole forest, as peaceful and beautiful as they were, have been replaced by a visually rich mosaic--expanses dominated by charred black trunks, meadows pink with a profusion of fireweed, dense young stands of pine, head-high stands of lush grass. It has become a stunningly beautiful and varied place.