Forest fires are raging across the Pacific Northwest of the United States, destroying human lives and forcing evacuations of homes. But for some natural species that have evolved to live with fire, the scenario is not so terrible.
Many animals and other organisms have evolved to treat – and even thrive after the flames.
Summer heat, dry air, strong winds and thousands of lightning bolts ignited and spread at least 21 separate fires in about a week, burning nearly a million acres. Oregon and Washington declared a state of emergency last week. (See “Forest Fires Intensify in Pacific Northwest as Winds Rise.”)
But “wildlife has a long-standing relationship with fire” in these regions, says environmentalist Mazeika Sullivan of Ohio State University, Columbus. “Fire is a natural part of these landscapes.”
For example, some predators see the fleeing species as an opportunity to eat. For example, bears, raccoons and birds of prey were seen hunting animals trying to escape the flames. (Read “Under Fire” in National Geographic magazine.)
Also, when the flames start, animals don’t just sit there and wait to be defeated. Birds will fly away. Mammals will run. Amphibians and other small creatures will dig into the ground, hide in logs or cover themselves under rocks. And other animals, including large ones such as elk, will take refuge in streams and lakes.
Gabriel d’Eustachio, a bush firefighter in Australia, says he usually doesn’t see many animals in fires, although a flaming bunny once surprised him. But he saw many invertebrates in front of the flames. “You’re overwhelmed by this wave of creepy walks marching in front of the fire,” he says. (See video: “Fighting Forest Fires.”)
“In those short-term situations,” says Sullivan, “there are always winners and losers.”
Danger and Death
Some animals die in the smoke and fire – those who can’t run fast enough or find enough shelter. Not all those dreadful creeps that d’Eustachio sees, for example, can escape.
Young and small animals are especially at risk in a forest fire. And some of their strategies for escape may not work – a koala’s natural instinct to crawl up into a tree, for example, might leave it trapped. (See “Koala Saved from Australian Fires.”)
Heat can kill too – even organisms buried deep in the ground, like fungi. Jane Smith, a mycologist at the U.S. Forest Service in Corvallis, Oregon, measured temperatures as high as 1,292 Fahrenheit (700 degrees Celsius) under logs burning in a forest fire, and 212 Fahrenheit (100 degrees Celsius) full two inches (five centimeters) below the surface. .
Scientists do not have good estimates of the number of animals that die each year in forest fires. But there are no documented cases of fires – even the really severe ones – exterminating entire populations or species.
As anyone who has ever experienced a house fire knows, the effects do not end when the flames are extinguished. The same goes for landscapes burned in a forest fire.
“People look at burned areas and think they’re dead. They’re not dead. They just changed,” says Patricia Kennedy, a natural biologist at Oregon State University in Union. “It’s a whole new habitat.”
Which can also mean new opportunities. In some places, for example, woodpeckers will fly and feast on bark beetles on dead and withering trees. “They love these invertebrates,” Kennedy says, then leaves when the beetles disappear.
Wild areas such as forests and prairies naturally grow and change in composition over time. An annual forest will have a different set of plants and animals living in it than a forest with 40 years. A commotion like a forest fire can serve as some sort of reset button, leaving an old forest to be reborn, Kennedy says. And “many species require that readjustment.” (See National Geographic’s forest images.)
Exactly what happens after a fire depends on the landscape, the severity of the fire and the species involved. But the event always causes a succession of changes, as plants, microbes, fungi and other organisms recolonize the burned earth. As trees and plants age, light and other properties change – and the composition of creatures in the area changes accordingly.
Streams and other water bodies flowing through a burned area can also change. Water flow, turbidity, chemistry and structure can be altered. Fish can leave temporarily. And there can be short-term killings between aquatic invertebrates that can affect animals on land.
“The water and the land,” says Sullivan, “are very connected.”
Let it burn?
Many species actually require fire as part of their life history. Heat from the flames can stimulate some fungi, such as morel mushrooms, to release spores. Some plants are sown only after a flame. Without fire, these organisms cannot reproduce – and everything that depends on them will be affected.
Over the past century in the United States, the natural progress of forest fires has often been suppressed. Fire prevention was promoted, and those fires ignited quickly extinguished before they could spread.
This has caused fewer species of trees and other plants to grow only in the years after a fire. It has also caused declines in some animal species that depend on this young post-fire habitat. “We’ve thrown the ecosystem so far away from a blow with a hundred years of fire removal,” Smith says. (See “Opinion: Don’t Log Burned Forests – Let Nature Cure Them.”)
Fire removal has even contributed to the decline of species now listed as endangered, Kennedy notes. The Kirtland philosopher is one example. These small songbirds of Michigan nest only in young pine forests. But the pine cones release their seeds only in fire. So without fire, much of the birds ’nesting habitat was removed.
As Kennedy says, fire is a bad thing when it happens in your backyard. But it can be a healthy event for a forest – and for at least some of the animals that live there.