morning of November 8, 2018, Allen Harthorn, a farmer who lives about two miles
from the town of Paradise, watched a dark cloud of smoke forming in the east
and began to worry about the safety of his and his neighbors’ homes. He also
began to worry about some other residents of the Butte Creek watershed—the
largest run of naturally spawned spring Chinook in California.
missed Harthorn’s home, but grew into the deadliest wildfire in California
history, blazing through 153,000 acres, killing at least 86 people, wiping out
over 18,000 structures, and devastating the foothill town of Paradise. Because
this fire was such a new breed—one that burned forests and wildlands as well as
cars, appliances, homes, and even septic tanks—scientists, fish advocates, and
resource managers are unsure of exactly what the impacts on the salmon will be
or how well they will recover.
who also heads up the Friends of Butte Creek and has worked for 20 years to
support recovery of the fish, was thrilled to see plenty of adult salmon in the
creek this summer. But he wonders about the fate of the juveniles that had just
emerged from the stream’s gravel to make their way downstream (and ultimately
to the Sacramento River, estuary, and ocean) when the fire struck. “They would
have had an 80- or 90-mile journey through various degrees of toxicity,” says
Harthorn. “[Plus] they were eating invertebrates and other microorganisms; they
very well could have been picking up toxic compounds.”
compounds were a result of the unusual nature of the wildfire, says Jackson
Webster, assistant professor of civil engineering at California State
University Chico. Jackson, along with several state agencies, began sampling
water quality in the creek as soon as the first rains began in late November,
shortly after the fire was contained. “This was an urban firestorm with
building after building igniting, but it wasn’t burning the tops of the trees.
It was driven by rolling embers pushed by wind on the ground,” says Webster.
appeared as if many of the burned homes’ concrete foundations captured a lot of
potentially contaminated sediment, he says, but the mobile home park that
burned was a different story, with runoff from those homes, which just sit on
slabs, heading directly for storm drains and the creek. Webster says as many as
30,000 cars burned as well—and their tires. “Many of those cars were sitting on
asphalt and draining into the storm drain,” says Webster, who saw the creek’s
waters running black, smelling of smoke.
Department of Water Resources and the Central Valley Regional Water Quality
Control Board also monitored water quality in Butte Creek, which is not a
source of drinking water for humans, during peak storms from December of last
year through May 2019. Those results show elevated concentrations of heavy
metals and PAHs (polyaromatic hydrocarbons), a byproduct of combustion that can
be toxic. Webster says levels of aluminum in particular were initially high
enough to affect the health of fish and aquatic life. But Clint Snyder, assistant
executive officer with the Central Valley Water Board, says the system is
continuing to flush itself out. “By May of this year those concentrations had
decreased quite a bit,” says Snyder.
state agencies and Chico State researchers will monitor water quality again
this fall and into next spring. “We’re still trying to figure out how to
measure any contaminants in the stream bed material that could be released into
the food web,” says Webster. In addition to collecting soil samples, he and
colleague Sandrine Matiasek, assistant professor of geological and environmental
sciences, collected some of the straw wattles that were placed to control
erosion, and will be analyzing any toxins they contain.
also be examining char, or burned wood, says Matiasek. “This char can act as a
sponge for contaminants that are not very soluble in water, so we’re interested
in understanding the role it plays and how it might filter contaminants, [as
well as] what happens if salmon are spawning in an environment rich in char.”
after the fire was tricky. The California Department of Fish and Wildlife was
unable to monitor benthic invertebrates, which sustain young salmon, or stream
gravels after the fire because so many staff members lost their homes during
the event and were scrambling to cope.
Gresswell, an emeritus research biologist with the United States Geological
Survey in Bozeman, Montana, who has studied the impact of wildfire on streams
for many years—albeit not this new kind of wildfire with a town burning in the
midst of a forest—says wildfires undoubtedly have an effect on invertebrates,
at least in the short term. “You might lose mayflies and caddisflies for a while
but different species come in and overall biomass remains the same.”
potential challenge for fish after wildfires is the loss of riparian
vegetation, which can lead to a lack of shade and elevated water temperatures.
But Clint Garman, an environmental scientist with Cal Fish and Wildlife, says
much of the riparian vegetation on Butte Creek did not burn or is starting to
rejuvenate. “Some of the trees that burned are contributing to large woody
debris that the juvenile fish will use as habitat,” he adds. The Friends of Butte
Creek have applied for a grant to prepare a restoration guide for landowners
that will include native and non-native plant identification and management,
and funds for tree planting, primarily in the riparian areas.
and fish advocates won’t know exactly how well the juvenile salmon survived the
fire’s impacts on the stream for a few years. The juveniles that out-migrated
last fall will come back as two-, three-, and four-year-old fish, Garman
explains. “Butte Creek adult fish are predominately three years old, so 2021
will be the year to look at adult returns.”
that last winter’s heavy rains after the fire helped the juveniles that
survived make their way to the estuary and ocean. He acted conservatively in
monitoring the juvenile fish this year—by not trapping them—to give them the
best chance to survive. “Especially under last fall’s circumstances, I felt it
best to leave them alone and let nature do what it does, without us adding
additional stress on them. I’m sure [the fire] didn’t help matters, but other
than the heavy metals, [these fish] have co-evolved with wildfire and turbid
water conditions throughout their life history,” says Garman.
adult salmon, which are resting in the stream right now, getting ready to
spawn, are probably helping the stream recover, Gresswell says. “Those salmon
will be working the substrate as they rebuild their redds, which helps mobilize
fine sediment and flush it downstream.” These adult fish do not eat for months
and rely on stored body fat to survive, from the time they migrate upstream
from the estuary and ocean until spawning, Garman explains. That means their
risk of consuming contaminated invertebrates is much lower than that of
the effort to clean up fire debris continues, activities that could have their
own impacts on the Butte Creek watershed. “There’s a massive amount of
construction, truck traffic, dust, erosion, that could have a secondary
effect,” says Webster. He and his colleagues continue to collect sediment
samples and are seeking funding to focus more on the sediments and potential
effects of contaminants on juvenile salmon.
continue to monitor the watershed this winter. Webster says he wants to better
understand not only how the stream environment is changing but also how long it
takes to recover. While recovery from the devastation continues, he sums up the
concerns of many: “What are the sources of contaminants? Is it the cars, is it
the trailer parks, houses, and how should we respond in the future? What should
our priorities be?”
Lisa Owens Viani is a freelance writer and editor specializing in environmental, science, land use, and design topics. She writes for several national magazines including Landscape Architecture Magazine, ICON and Architecture, and has written for Estuary for many years. She is the co-founder of the nonprofit Raptors Are The Solution, www.raptorsarethesolution.org, which educates people about the role of birds of prey in the ecosystem and how rodenticides in the food web are affecting them.