Last fall, in the midst of burned and charred trees left in the wake of Yosemite National Park’s Rim Fire, I participated in, of all things, a wedding.
It was the most beautiful wedding I have ever attended. The contrast of the light colors of the bride’s dress and our group’s heady happiness set against the backdrop of black trunks and gray ash brought an intensity of meaning to the affair; new lives beginning while somewhat older lives were washed clean to sprout and start again. After all, fires have always been essential to the health and ecology of Western forests.
However, recent blazes—sprawling, raging infernos such as last year’s Rim Fire in California—may be a lot different from those of the past. And so, biologists fear, will be the ecosystems that grow in their wakes.
A different kind of fire
Historically in the Sierra Nevada, low-intensity, natural fires would burn intermittently through the understory, allowing the mature trees to survive and leaving behind only scattered patches of severely burned forest—usually between a quarter acre and a half acre. Rarely did such parcels exceed 10 acres.
The giant Rim Fire of 2013—the biggest wildfire on record in the Sierra Nevada—however, had a high-severity burn area of more than 63,000 acres, where trees were left blackened and dead. Such extreme fires can vaporize foliage and leave little in the way of seeds, nutrients, shade or moisture to enable a forest to rebuild itself. If a place experiences such a fire, you may not see trees growing in it for a long time.
What’s causing this metamorphosis of fire behavior that’s turning our Western forests into “bombs” that go off every summer? While most agree that there’s no single factor that’s responsible—theories from historical fire patterns to the effects of bark beetles on fuel loads have been postulated—there are two factors where broad consensus exists: Smokey Bear and climate change.
Blaming the bear
From 1911 through the early 1970s, Smokey Bear’s message made it clear that the goal of state and federal land management was to extinguish, as quickly as possible, all fire from the woods. The result: a timbered landscape that tends to be both mat-dense and homogeneous, with surface fuels piling up in some forests for a century or more. In once open forests, such as the central and southern Rockies’ stands of ponderosa pine, this abundance of fuel is highly combustible, feeding white-hot crown fires in ecosystems better adapted to low-intensity ground blazes. While ponderosas in open forests can withstand the latter, high-intensity events can reduce groves of even robust pines to patches of bare dirt. Because of Smokey’s fire suppression message, forests from Alaska to Arizona grew dense with fuel, leaving them prone to burning at high intensities.
Denser forests are also less resilient to disease, drought and warmer temperatures, all hallmarks of the West’s changing climate.
A changing climate as the cause
Scientists have long predicted that climate change would lead to more extreme wildfires. The combination of higher temperatures and lower moisture tends to produce larger and more frequent fires. Even a small temperature increase can have an outsize impact on water evaporation. (Average summer temperatures in the U.S. have risen from 70.5 degrees from 1901 to 1910, to 71.7 degrees from 1981 to 1990, and to 73.7 degrees in 2012.) In fact, according to the United States Environmental Protection Agency, with even a one- or two-degree increase of global average temperatures, it’s predicted that there will be a 200 percent to 400 percent increase in the area burned by wildfire in parts of the Western United States. In addition, earlier snowmelt extends the fire season, which in parts of the West is already 10 weeks longer than it was 15 years ago.
In the West, the annual burn area is already more than six times larger than it was 30 to 40 years ago. Today’s blazes, instead of being healthy, rejuvenating parts of a natural cycle, cause forests to go through a process known as “type conversion.” Areas severely burned by the Rim Fire, for example, may see only grasses, shrubs and a few shade-tolerant but fire-sensitive trees, such as white fir and incense cedar, where once ponderosa pines and sequoias grew. Rather than the exception, fires such as the Rim Fire are probably going to become the norm. That could mean a very different future for the grand forests of the West.
I often go to the same places I’ve visited before, to see how they’ve changed through the seasons, time and temperatures and to discover how we both have grown. When I revisited the Yosemite area last fall, I did find the charred forest beautiful. Perhaps that was because I assumed new life would spring from the ashes.
I may have been wrong.
Do you think the forests we know today are an endangered landscape? Will the “forests” of the future be treeless?
Here’s to finding your true places and natural habitats,