Some ecological tradeoffs part of post-burn process
Animals and birds flee when a wildfire engulfs their home, but some species soon return to take advantage of food and nest sites created by the blaze.
Escape can be difficult for animals that don’t move fast, and some individuals do perish, said biologist Kent Woodruff. But some animals and birds actually depend on fire for food and habitat, he said.
Many chipmunks, mice, crickets and snakes — which move pretty slowly — probably perished in this summer’s fires. But three to four years after a burn, biologists see a huge resurgence in these creatures, said Woodruff, who retired recently after a long career with the Methow Valley Ranger District.
Small rodents thrive after a fire because the low-growing vegetation, berries and seeds they rely on proliferate after taller trees burn. A live tree takes up hundreds of gallons of water a day so, after it dies, that water becomes available to plants and animals on the forest floor, said Woodruff.
Larger mammals and most birds can generally move fast enough to flee a fire, although scientists occasionally find deer, bears and cougars that got trapped by flames and died, said Woodruff.
Smoke stresses animals and can make them more vulnerable to predation. Although some animals suffocate, healthy individuals typically rebound when the smoke lifts, said Woodruff.
“For most animals, in the long-term, their populations — their great-great grandkids — will be fine,” said Woodruff.
“Fire is a natural part of the landscape, and for 10,000 years the West has been burning and smoky,” said Woodruff, noting that many species are adapted to this cycle.
Still, although animals evolved to thrive in a fire regime, climate change is significantly altering that natural cycle by making fires and smoke more intense, said Woodruff. “We can’t just think that we’ll get through this and all will be fine,” he said.
Although birds will fly away from an area that’s actively burning, there is significant evidence that birds are affected by air pollution including smoke, said Olivia Sanderfoot, a quantitative ecologist who is studying the ramifications of air pollution on birds.
Sanderfoot cited consistent evidence that smoke and other pollutants suppress birds’ immune systems, affect their behavior, and impair their reproductive success. Even in species that benefit overall from wildfire, the toxic components of smoke will have a negative impact, she said.
Julie Hovis, a biologist who studies and tracks migrating birds, has seen fewer birds than expected for this time of year. Because these birds have finished breeding, some may be starting their fall migration early, she said.
Heavy smoke can create problems for birds such as swallows that catch insects as they fly, said Hovis. But after a fire, these birds flourish, drawn by new openings in the forest that attract insects, according to the National Audubon Society.
Smoke also creates other adversities. Hawks depend on sight to find prey as they soar, so they are most likely affected by the thick smoke that hung in the valley for most of August, said Art Campbell, president of the North Central Washington Audubon Society. Some studies suggest that birds can be so overwhelmed by smoke that they can’t escape, said Sanderfoot.
The smoke is less of an impediment for migrating birds, which rely on many cues in addition to sight — including the intensity of light, reading the landscape, electromagnetic signals, and stars, said Sanderfoot. Migrating birds may also fly high enough that they are above the smoke, said Campbell.
Fires often mean ecological trade-offs. Pileated woodpeckers, which need living forests with mature trees, have lost hundreds of thousands of acres of habitat in the Methow Valley to wildfires in recent years, said Woodruff. But black-backed woodpeckers, which eat the larvae of beetles that invade charred trees, need burned forests for food and nesting areas.
Northern hawk owls also prefer post-fire forests. In fact, the first evidence of hawk owls nesting in the Methow was found after the Needles Fire, which burned near Lost River 15 years ago, said Woodruff. The owls, which prey on chipmunks and other small rodents, found an abundant food supply a few years after the fire.
“There are certainly winners and losers when the habitat shifts from dense forests to more open forests,” said Woodruff.
After the Carlton Complex Fire in 2014, Northern pygmy owls, which nest at higher elevations in coniferous forests, flooded into the valley in the late summer and fall as they left burned areas in search of prey, said Campbell. The following year, the owls, which eat small mammals, rodents and small birds, were back in the forest along with their food sources, he said.
Although biologists and citizen scientists record wildlife observations during and after a fire, there has been relatively little in-depth research. Conducting a comprehensive study to track species before and after a fire would be costly, and funding hasn’t been available, said Woodruff.
Sanderfoot points to a potential upside of the choking smoke that has persisted over Washington and Oregon this summer. “The smoke is a reminder about what we stand to lose and what wildlife stands to lose,” said Sanderfoot. “We can take steps to change that.”