Sometimes, to understand what’s happening in a stream, scientists have to go fishing.
“I’m ready whenever,” says David Leer of CreekWalker Aquatics, who’s leading a field crew of scientists and technicians. “Fire in the hole.”
The “fire” he’s referring to is electricity from an electrofishing rig he’s carrying on his back. Electrical current enters the water by way of a metal probe he waves in the water in front of him.
It’s a hot day in mid-July, and Leer is knee-deep in remote and rocky Cedar Creek in the Willamette National Forest east of Salem. The forested hills around the stream burned in the Beachie Creek Fire — one of Oregon’s 2020 Labor Day fires.
The electrofishing unit’s relentless beeps are jarring interruptions to the serene scene that surrounds him.
“If you can hear the beeping and you put your hand in the water, you’re probably gonna get a little jolt,” he says.
The mild electrical current is designed to temporarily stun fish and other creatures in the water so the crew of researchers can scoop them up.
“The fish are doing their best to hide from us,” says Allison Swartz, a stream ecologist at Oregon State University.
“Yep, yep, yep, yep, yep,” she yells as she spots a stunned fish floating to the surface. She scoops it up with her net. “That was a rainbow trout.”
All the fish, tadpoles and froglets, crayfish and giant salamanders they catch will be counted, weighed and measured before being released back into the stream.
“We’re trying to understand how burned stream systems function differently [from] unburned systems,” Swartz says.
The data the researchers are collecting will help reveal how streams changed following the Labor Day fires — one of the most extreme fire events in the state’s history.
Wildfire is often thought of as being detrimental to stream ecosystems because of higher post-fire water temperatures and additional sediment washing into the waterways from burned landscapes. But Cedar Creek and other streams burned in the fires are proving otherwise.
“Everything we thought we knew about fire, we’ve kind of turned it on its head here on the west side of Oregon,” says fish biologist Brooke Penaluna, with the U.S. Forest Service’s Pacific Northwest Research Station.
Streams after the burn
“I remember it very distinctly,” says Ashley Coble, program manager for Western watersheds for the National Council for Air and Stream Improvement, a national timber industry-funded research organization. “Labor Day 2020. COVID. Everything was closed. We were in the river that day. It was quite hot. … It was a glorious day until it wasn’t.”
That day, a massive windstorm moved across the Pacific Northwest, fueling more than 20 fires from Washington south to California. The fires would eventually burn more than a million acres in Oregon alone.
“How rapidly all of these megafires spread was really unique. We knew immediately that these were massive, huge fires. We had no idea when they’d be put out,” Coble said.
When the fires were finally out, 11 people were dead and thousands of homes and businesses were destroyed.
In addition, there was concern about the extent of damage in in the forests because streams and rivers in the Cascade Range provide drinking water for millions of Oregonians.
“We knew it was bad, and we knew that it needed to be studied,” Coble said.
A team of federal, university and nonprofit biologists and ecologists sprung into action. They wanted to figure out how different styles of forest management interacted with different intensities of wildfire to impact Cascade streams.
To do this, they identified 30 streams that had burned at different severities across tree plantations, older natural forests, areas where the burned trees were salvage logged after the fire, and some in areas that hadn’t burned for comparison.
Every summer since the fires, crews have tested stream water for sedimentation, water temperature, flow rate, nitrogen, oxygen, phosphorus and organic carbon. They’ve also checked to see how the animals in the streams have fared.
Many of the target species depend on clean, cold water to flourish. But much of what’s left around Cedar Creek are trees that look like charred matchsticks. Without a living tree canopy, the hot sun beats down on the water much of the day.
In spite of this, Swartz has started seeing some surprising trends on many burned streams.
“Despite stream temperatures getting really warm in these systems after the fire, the fish populations are remaining ... just as high or higher than the unburned sites,” she said.
The researchers are still unpacking exactly why this is happening. One theory is that more sun means more algae, which feeds the aquatic food web. Also, without trees and vegetation sucking up water on stream banks, there’s more water left for the rivers.
“With the extra rains that are coming straight down and into the stream — with that runoff — you’re getting additional fringe habitats along the streams,” Penaluna said. “So it could either be because of the food webs, it could be because of the increased habitat, and I think the jury is still out on which one is driving the responses that we’re seeing on the west side of Oregon.”
And it’s not just fish. Streams in the west Cascades are home to coastal giant salamanders and tailed frogs.
Preliminary results are showing that the wildfires haven’t caused declines in amphibians either. However, the researchers have seen fewer frogs in places where heavy post-fire salvage logging happened.
Looking ahead
To truly understand the ecological impact of wildfire on the landscape, researchers have to play a really long game.
“This is our fifth year of collecting data across these 30 different streams, and we are going to do it again at year 10,” says Penaluna.
She hopes to continue the study through the 15th and 20th anniversaries of the Labor Day Fires, as well.
Coble says it will take these extra years to understand the full impact of fire severity and different styles of forest management on the streams. And she says it’s important to try to tease out what is actually pushing the changes they’re seeing: Is it how hot a fire burned around the stream? Or how the forest was changed by humans before and after the fires? Or something else?
“I think one of the key questions is, ‘How do we manage our riparian zones in the most efficient ways for recovery for aquatic ecosystems?’” she says.
Answering these questions could inform how heavily burned forests are salvage logged and where and how intensively trees are replanted near streams on private and public lands.
For the longest time, stream ecosystems were thought to suffer because of wildfire. But in the five years since the Labor Day fires, these scientists are seeing signs that the trout and other species that call the Cascades home are thriving.
The research shows that the tragedy of the Labor Day fires offered a research opportunity to figure out the best way to manage our forests after wildfire to protect our streams and all the life they contain.
“The reality is that wildfires are increasing on the landscape in severity and size,” says Swartz. “So in terms of understanding how we manage our forests and these ecosystems, we need to know what’s happening because we’re really just kind of at the start of what we’re going to begin to see in the future.”
This story comes to you from the Northwest News Network, a collaboration between public media organizations in Oregon and Washington.
