To Save the Redwoods, Scientists Debate Burning and
Logging
December 16, 2019 by Becki
Robins
Millions of people travel to
California’s redwood forests every year to marvel at the few remaining stands
of old-growth trees. Sequoia
sempervirens, or the coast redwood, thrives in the damp
climate along the Pacific Ocean. Some are more than 2,000 years old, and the
tallest can reach 380 feet. The state is also home to a second type of giant
redwood, Sequoiadendron giganteum, or giant sequoia. The
world’s most massive tree, it grows in the inland Sierra Nevada mountains,
sustained by melting snowpack. The oldest sequoias are 3,000 years old, and
although not as tall as coast redwoods, they are wider, sometimes reaching an
impressive 30 feet in diameter.
Redwoods draw crowds, but they are also ecologically
important. They act as natural water filters, processing trillions of gallons
of clean, drinkable water every year. Redwood forests store at least three
times as much carbon as any other kind of forest, and because the individual
trees live for thousands of years, the carbon storage is long-term. That makes
them important actors in the story of California’s changing climate.
But today, the redwoods are in danger. Climate change,
pathogens, and years of misguided forest management practices have helped make
wildfire California’s signature menace, and even these ancient trees are not
immune. In 2008, for example, the Basin Complex Fire swept through the coast
redwood groves of the Los Padres National Forest, burning for more than a
month, destroying 58 structures, and forcing the evacuation of the entire town
of Big Sur. The blaze consumed more than 160,000 acres on its way to becoming
one of
the largest fires in California’s history.
The circumstances that enabled the Basin Complex Fire
haven’t improved much in the last decade. That’s why groups tasked with
protecting the old-growth trees — including the state and national parks
systems and the nonprofit Save the Redwoods League — practice active, hands-on
management. This includes controlled
burns and “restoration
thinning,” the harvesting of smaller, younger trees to make way for
older, larger ones.
Echoing many of the world’s forest agencies and
preservation groups, Save the Redwoods League, which celebrated
its centennial last year, says active management is the best way to
guarantee the regrowth and preservation of forests in the aftermath of
clear-cutting and in the modern era of climate change.
And yet, a century of forest management still hasn’t
made clear if this is true for redwoods. Some environmentalists say forest
thinning is simply logging by another name — a charge that goes back to the
early 1900s, when logging was at its peak. Since Europeans began to settle permanently
in California, 95
percent of the state’s old-growth coast redwoods and 33 percent of the
old-growth sequoias have been lost. Today, some activist groups and
scientists say these majestic trees would do best if left alone.
“As with everything in the natural world, it’s
complicated,” says Jodi Frediani, a former environmental consultant and
resident of the Santa Cruz Mountains who has been advocating for the redwood
forests since the 1970s. “We only ever seem to know a part of the picture. And
when we attempt to manage, we very often do damage.”
Prior
to the 20th century, the periodic wildfires that swept through the
giant sequoia forest system helped create a nutrient-rich soil and kept the
understory free from the brushy undergrowth that would otherwise out-compete
young sequoia trees. But then, in
1910, a series of devastating fires spread across the western U.S. By
1926, the United States Forest Service had adopted a policy of fire suppression
for all fires covering 10 acres or more. The objective was total fire exclusion
— keeping all fire out of wildland areas — in order to reduce the loss of
resources and minimize firefighting costs.
But fire exclusion brought unintended consequences.
When excess vegetation is allowed to grow, it creates the perfect conditions
for devastating megafires, which burn faster and hotter and can potentially
kill the old-growth trees that would have easily survived smaller fires.
California’s recent drought has exacerbated the problem, spurring tree deaths.
“There’s like 100 and something million dead trees in the Sierras right now,”
says Richard Campbell, director of restoration at Save the Redwoods
League.
Prescribed
burning is one way to undo the damage caused by fire exclusion,
Campbell says. A prescribed burn is a fire that’s planned and executed by
people, and in modern forestry it’s one of the most important tools for
managing forests. Forest managers set these fires under tightly controlled
conditions that take into account things like public safety, weather, and
specific objectives for the trajectory and end goals of the fire.
Prescribed burning has been practiced in the giant
sequoia forests since the 1960s, when the
ecologist Harold H. Biswell began studying fuel reduction in redwood
stands near Sequoia National Park, earning himself the nickname “Harry the
Torch.” Two decades later, when the Pierce Fire moved through Sequoia National
Forest, it burned old-growth trees. But when the blaze entered the Redwood
Mountain giant sequoia grove — a part of the park that
had been subject to a controlled burn a few years prior — it became less
intense and crews were able to contain it.
The coast redwoods face a different set of
circumstances, though, says Kristen Shive, director of science for Save the
Redwoods League. Fire exclusion has not been as harmful for these forests, she
says, because the climate is wetter. In a damp forest, the vegetation doesn’t
dry out as quickly and the microorganisms that live in the damp soil help the
woody debris on the forest floor break down a little faster.
In a 2014
paper published in the Open Journal of Forestry, environmental
studies professor Will Russell and his colleagues at San Jose State University
wrote that active forest management of the coast redwoods might not be necessary.
“In many forest types,” they wrote, “especially coast redwood forests, natural
regenerative properties allow the development of old-growth characteristics
over time without the need for additional active management.”
“Redwood trees are very fire-resistant,” adds Frediani,
who has observed the effects of several smaller fires that swept through the
redwood forests near her home. “Even 4-inch diameter saplings, their bark was
[merely] scorched,” she says. “They didn’t go up in flames.”
Recent research doesn’t necessarily agree with
Russell’s and Frediani’s assessment, though. A 2017
paper published in the journal Forests argued against interpreting
the coast redwoods’ “ease of regeneration” and “rapid growth rates” as an
indication that these giants can recover without human assistance. The authors
noted that Russell’s research was conducted in unnaturally structured,
second-growth forests, which are the forests that grow after a clear-cut harvest
or other disturbance. Because old-growth forests are complex systems full of
trees of varying ages, the authors argued that Russell and his coauthors had
overestimated how quickly a second-growth forest, where most of the trees are
of similar age, could achieve an old forest structure. (Russell says that he
and his students have since collected additional data that further bolsters his
earlier findings.)
Other studies have concluded that there may be some
drawbacks to active management, specifically thinning. An influential 1983
study published in the Journal of Forestry found that redwood sprouts grew more
slowly after thinning than they did if they remained unthinned. That and
similar evidence are enough for some scientists to argue that the true impact
of active management is still an unknown. Meanwhile, others say that the slower
growth is simply a variable to be considered during active forest
management.
Save the Redwoods League believes that active
management will increase the forests’ resilience in the face of increasing
wildfire threats, including the pathogen Phytophthora
ramorum, which causes sudden oak death. This fungus-like organism
has gained a foothold in parts of the coast redwood forests, and while it does
not infect the redwoods themselves, it was implicated in
the Basin Complex Fire.
Old-growth coast redwoods are ecologically different
from California’s other forests. A diverse community of animals and plants —
including tanoak trees — live in the understory. When the sudden oak death
infects a tanoak, says Campbell, it kills the tree standing. The tanoak then
begins to decay and break apart, creating a pile of highly-flammable material
on the forest floor, under a dry but still-standing trunk. Fires in forests
impacted by sudden oak death, Campbell says, burn hotter and climb higher,
which puts the otherwise fire-resistant old-growth trees at risk.
Ultimately, the debate over forest
management encompasses more than the interpretation of data. In fact, much of
the outcry against thinning has its roots in the fraught history of logging in
the state of California, and in a deep mistrust of the true motives for cutting
down redwood trees. Russell thinks some of the forest management work Save the
Redwoods League is doing is counterproductive, especially when it involves
removing trees.
“They are doing thinning,” says Russell, “and that’s a
funny word because it used to mean, at least in terms of restoration, thinning
smaller, unmarketable trees.” Today, Russell says, Save the Redwoods League
uses the word “thinning” to describe commercial logging, which is now being
done in Redwood National Park under the banner of forest management. “They’re
selling logs for income and then saying that this is also improving the forest
recovery and reducing fire hazard.”
Campbell downplays the economic significance of
thinning. “Most of the wood that is cut and felled is not merchantable,” he
says. “It’s generally too small to be sold.” When economic opportunities do
arise in the second-growth forests where logging is currently taking place,
Campbell says that Save the Redwoods League doesn’t necessarily refuse them.
But the organization is transparent about it, and Campbell says money is never
the motive: “Every action that we take does have the stated explicit goal of forest
restoration.”
Without active forest management, Save the Redwoods
League says the forests might recover, but they won’t be the same as they were
prior to the destructive timber management practices of the 20th century. “An
entire giant sequoia grove will burn down and of course, something will grow
there,” says Shive. “It’s not that if we don’t do something there will never be
a forest again.” But, she says, the forest that grows there naturally may not
feature sequoias, and it may no longer meet the habitat needs of the species
that are native to the original forest system — the sword fern, redwood sorrel,
huckleberry of the coast redwood forest, the sweet cicely, white hawkweed, and
wood violet of the giant sequoias, and the hundreds of other plants, animals,
and microorganisms that grow in the shadows of these ancient trees. That’s why
people need to step in and guide the recovery in the right direction, she
says.
“You could throw up your hands and say, we messed it up
too much, let’s just walk away,” says Shive. “And I understand why people
sometimes feel like doing that because ‘Oh, are we going to mess up again?’ But
I think the best we can do is take all the best available science and spend
some time in the woods, to better understand the forest, and then make the best
decisions that we can.”
Becki Robins lives in California’s gold
country and writes about science and nature, history, and travel. Her work has
appeared in Earth Island Journal, Lonely Planet, and on the YouTube series
SciShow.
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