How animals are adapting to the rise of wildfires
Lizards that can outrun blazes. Birds that lay ash-colored eggs. Wildlife may have a limited ability to evolve in this fiery new era known as the Pyrocene.
As climate change increases global temperatures, wildfires (pictured, a blaze in Botswana’s Okavango Delta) will become more intense, common, and last longer.
PHOTOGRAPH BY BEVERLY JOUBERT, NAT GEO IMAGE COLLECTION
As wildfires burn more frequently and intensely, across larger geographic areas and longer seasons, scientists estimate they now contribute to the extinction risk of at least 1,660 animal species worldwide.
It’s one more consequence of the so-called Pyrocene, a term coined by environmental historian Stephen Pyne, emeritus professor at Arizona State University, to frame our current epoch as one shaped by humans’ exceptional ability to manipulate fire.
“We developed small guts and big heads by cooking food; we climbed the food chain by cooking landscapes; and now we have become a geologic force by cooking the planet,” reads the description of Pyne’s 2021 book The Pyrocene: How We Created an Age of Fire, and What Happens Next.
Might animals be able to adapt to life in the Pyrocene? Ultimately, it’ll depend on two things, says Gavin Jones, an ecologist with the USDA Forest Service who studies fire-driven animal evolution. First, whether some individuals of a species are better than others at surviving fire and its aftermath.
Second—and most importantly, he says— whether those abilities are caused by genetic differences that fire survivors can pass down to their offspring.
Here are some of the fire adaptations scientists have discovered so far.
Waiting it out
Some species have already evolved ways to survive fires. In Australia, for example, the yellow-footed antechinus, a small, mouse-like marsupial, hides in its deep, rocky burrow in a state of torpor until the fire burns out.
Frillneck lizards stay out of flames’ reach by climbing termite hills or trees. As wildfires become more intense or last longer, however, such strategies may backfire. If the flames reach too high or the fire gets too hot or rages on for too long, even these animals will die.
A yellow-footed antechinus peers out from its den in Western Australia.
PHOTOGRAPH BY JIRI LOCHMAN/NATURE PICTURE LIBRARY
Faster runners
Other species that have long lived in fire-prone areas do what humans do: They evacuate—as fast as possible. In the United States, Eastern fence lizards living in recently burned habitats can run faster than their counterparts living elsewhere, a 2018 study found.
It’s unclear, however, whether this is due to natural selection, which might occur if the slowest lizards simply could not outrun the fire and died, or whether there may be another reason why individual animals become faster in recently burned habitats.
For example, since it may be easier for lizards to warm up their cold-blooded bodies in the more open, darkly colored areas recently burned by wildfire, they might over time develop stronger muscles there.
Easier hunting?
And other animals, such as the black-backed woodpecker, rely on forest fires for food and shelter. “They feed on the beetle larvae that live in the dead trees in recently burned forest,” Jones says, and make their nests in the cavities of dead trees.
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It remains to be seen if they can adapt to today’s world of hyper-intense wildfires.
What they really need is pyrodiversity, researchers suggest —a mosaic of intact, burned, and severely burned forest. As fires become bigger and hotter, however, burn zones are becoming more monotonous and therefore less appealing.
Blending in
Surviving a fire is one thing; surviving its aftermath is another. Much as dark-colored peppered moths in England evolved to outnumber white ones as the Industrial Revolution coated tree trunks in soot, some animals today are likely to be darker in places where wildfire is more recent or common.
Pygmy grasshoppers, which can range from black to nearly white in color, were 50 percent more likely to be all black in parts of Sweden affected by a wildfire in the past year, likely because they’re less obvious to predators, researchers found.
In areas of the coastal plain of the southeastern U.S, the landscape mosaics created by frequent wildfires were associated with more coat colors in fox squirrels, which have more color variations than any other mammal in North America, from pitch-black to agouti (grayish brown) to pale gray.
“Since fire creates a range of environmental conditions that can change rapidly, there’s no single color that will always be best in fire-prone areas,” explains Alex Potash, a postdoctoral researcher at the University of Florida.
“So the population maintains wide variation in color between individuals. Cropland, on the other hand, is comparatively stable, which creates a selective force for a single best squirrel coloration for the area, generally a pale silvery gray.”
A Temminck’s courser sits on its eggs on the burnt ground.
PHOTOGRAPH BY JOHN CADDICK
The eggs, with speckles and streaks of blackish brown on gray, blend perfectly into the charred earth, as seen in Zambia.
PHOTOGRAPH BY JOHN CADDICK
While the proportion of animal color variants currently fluctuates with annual variations in fires, the fact that these changes can happen at all suggests there might be a way for these species to adapt to fires’ changes to the landscape—at least, if they survive the blazes first.
This is what appears to have happened with Temminck’s coursers, a ground-nesting bird in sub-Saharan Africa. All females lay ash-black eggs that blend in perfectly with recently burned patches of the fire-prone savanna in which they live.
Strong genes required
For animals to evolve in response to more frequent fire, genetic variation is crucial. Though there have been no genetic studies specific to fire adaptations, Jones says, a study published in Science in 2020 found a surprisingly large amount of genetic variation in 19 well-studied species, suggesting those animals do have the ability to rapidly evolve.
There is some evidence, however, that more frequent or larger fires might compromise genetic variation. In southeastern Australia, for example, populations of the native Mallee emu wren are increasingly small and isolated because of wildfires, which prevents them from mixing and causes them to lose genetic diversity over time.
Cactus wrens in coastal southern California face a similar challenge. In contrast, fires may help other species connect. In Yosemite National Park, lupines often replace other burned vegetation, allowing populations of Boisduval’s blue butterfly populations to expand and mingle.
Spark of hope
Improved fire management could also play an important role in protecting animals in the Pyrocene.
“Preventing accidental fires is important,” Jones says, “but fire is a natural part of many ecosystems. So creating conditions where fire can burn in a safe way, and using controlled burns to remove some of the fuel can prevent larger, more intense fires.” (Does wildfire smoke impact animals? Here’s what we know.)
Not only can controlled burns prevent some of those intense, modern-day infernos that animals can’t possibly survive, but they could help maintain animals’ existing adaptations to fire by rewarding the best-adapted ones and eliminating the ones that wouldn’t stand a chance in an actual wildfire.
Controlled burns also may provide a relatively gentle introduction to fire for animals that aren’t experienced with or adapted to it, giving them a chance to learn what to do when things get worse.
“I definitely don’t want to paint an overly optimistic picture,” says Jones. “Many species may not be able to adapt rapidly enough. But I think there’s a spark of hope that some of them will.”
