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Nature’s Path Back

Wildfire and wildlife—what’s the first image that comes to your mind?  I’m 7 years old, sitting in a darkened movie theater, watching the fire scene in the Disney animated classic Bambi.  Birds, squirrels, rabbits, raccoons, our protagonist deer all flee through scorching embers, swirling smoke, and crashing, flaming branches.  That scene seemed to last for hours, although it actually wrapped up in about 3 minutes.  But more than 60 years later, I remember how scared that little girl felt as clearly as if I had just left the theater.

But if you watch that scene again (or remember it better than I did), you’ll note that it ends well.  Many animals make their way to a place of safety.  And, in fact, such an ending is likely for much of the non-cartoon wildlife that find themselves in wildfires, too.  Animals that can run, run.  Those that can fly, fly.  Those that can burrow, burrow.  By and large, they got this.

As fire rages, the temperature above ground may reach 1,600o F; yet two inches below the surface, the air may register still bearable temperatures.  Many species—lizards, ground squirrels, mice—survive fires by hunkering down in underground burrows.  Mortality among adult birds typically is low although, if a fire strikes during nesting season, the young likely perish.  But the adults can move to a safer spot and start what is called a “replacement” clutch.  Some species—e.g., Hairy and Black-backed Woodpeckers—seek out burn areas because of the abundance of insects eating dead wood in charred trees.  Observers have reported that large mammals can appear amazingly calm in close proximity to flames.  For example, during the massive fires in Yellowstone National Park in 1988, bison, elk, and deer rested and grazed within 100 yards of torching trees.  Large mammals can also take refuge in streams and lakes. 

Of course, wildfires do kill some animals.  Small mammals that construct surface-level nests, such as woodrats, are more vulnerable because their nests are made of dry, flammable grasses and twigs.  Even large mammals can have difficulty escaping wide, racing flames or fires that surge across the tops of trees.  Fast-moving, wind-driven fires such as Northern California’s Camp Fire in November 2018 moved too quickly for some animals to outrun as it created its own firestorm. Most of the large mammals that died in the Yellowstone fires succumbed to smoke inhalation due to thick ground smoke.

But populations of most species as a whole exhibit, at worst, only temporary impacts of wildfires, primarily through changes in food and shelter options.  Research has shown that numbers of individuals and species of birds as well as both large and small mammals tended to drop for the first year or so following a major fire.  Even in very extensive fires, though, pockets of habitat often remain untouched throughout the charred landscape, offering nearby refugia and relocation sites.  Areas that do burn usually produce stronger, nutrient-rich grasses and forbs soon after a fire; grazing mammals move back quickly to enjoy the nutritious new forage.  Many times, post-fire forests are clear-cut.  But if they aren’t, small mammals and other animals begin making use of them just a few seasons after wildfire. By about seven years post-fire, if no other fires occur, levels of wildlife density and diversity tend to be indistinguishable from those in similar habitats that experienced no fire.  Moderate fire can also result in a wider variety of micro-habitats, from open meadows to re-growing forests, providing a diversity of biomes supporting multiple species.  As trees and other plants age, light and other features change; the composition of creatures in the area shifts in response.

Wildfire can still negatively impact wildlife in the short term. Chipmunks, which rely on live trees more than many other rodents do, generally leave a burned area and don’t return until new-growth trees reach sufficient size to provide appropriate food and shelter.  Displaced animals must compete with residents for limited food, shelter, and water.  For birds, migration paths consist of a series of “rest stops:”  areas providing shelter and food to rest and replace some of the energy lost during the long trek.  If these areas burn, birds have to either search for other spots or continue on without resting and refueling.  Either way, migration becomes even more of a challenge than it typically is.

Long-term problems can occur as well.  Fish especially can suffer long-lasting impacts.  Air drops of fire-retardant slurry generally avoid waterways. But sometimes slurry inadvertently finds its way into streams and creeks, fouling the water.  Debris and ash can end up in creeks and rivers, clogging the gills of the fish and generally polluting the waters.  Rains may send debris, ash, soot, and mud cascading into streams and rivers months—even years—afterward, in the absence of the anchoring cover of grasses and shrubs.  As a result, the impacts of fire on fish habitat can endure.  (Note, though, that in some instances, streams and rivers may quickly replenish with nutrient inputs and increased habitat complexity—both beneficial for fish.)  Moreover, fires that return after five or fewer years can permanently change the habitat type—e.g., from shrubland to non-native annual grasslands, which may provide a less productive habitat for wildlife. 

Regardless of the final outcome, a fire event always sparks a succession of changes as plants, microbes, fungi, and other organisms recolonize the burned land and survivors adapt. For humans, fire can be catastrophic, especially as we build combustible houses reaching deeper and deeper into traditionally fire-prone areas.  Furthermore, as much as 85% of our more recent fires have been ignited by human-related activities (e.g., faulty power lines, careless use of fire).  But wildlife have co-existed with wildfire for centuries.  Some will move away permanently. Others will return surprisingly quickly.  Still others will return slowly over time.  Yet even as the humans reel from the shock, disruption, devastation, and heartbreak, most wildlife have already started to adjust to their new post-wildfire surroundings.  Yes, indeed.  They got this. 

Image Copyright ” California Wildfires View From Escondido ” by Leia Parker under CCA 3.0

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