The
world’s forests are
simultaneously climate
powerhouses and victims,
sucking carbon from the air
while facing myriad global
warming impacts—from
wildfires to pest
outbreaks.
Recent
research found that climate
change is already driving
widespread disturbances in
European forests and, by the
end of the century, will
likely transform the
landscapes that communities
depend on.
My
colleague Bob Berwyn has
been covering climate
science and forests for
decades, and recently wrote
a story about this
unsettling forest forecast.
I asked Bob to tell me more
about how he first got
started reporting on
forests—which are much more
diverse than people may
realize—and explain what
this research could mean for
the future of these critical
ecosystems.
When
did you first become
interested in forests?
I’ve
been interested in forests
since I was very young and
wanted to know where they
came from and why they grew
in some places and not
others, so I started
learning about the
geological history of Earth,
and how forests grew after
big glaciers and ice sheets
retreated from North America
and Europe.
And
for me, growing up in a
part-European culture,
forests were also places
that held mysterious and
powerful life forces,
manifesting in stories about
fairies and druids.
Have
there been any moments
that really struck you
while reporting on climate
change’s impact on
forests?
In
the early 2000s, my
11-year-old son asked why
all the huge pine forests
around our Colorado
neighborhood were turning
brown and red. I was
reporting on a destructive
epidemic of pine beetles
that was causing the
die-off, but it was still
hard to describe to Dylan
how climate change had
tipped the balance against
trees that had stood for a
century or more, and were
part of his outdoor
playground growing up.
The
overwhelming outbreak killed
about 90 percent of mature
lodgepole pines growing
across millions of acres in
less than a decade. All the
scientists studying the
event pointed at a warming
climate and more severe
droughts as the trigger,
stressing trees and
promoting beetle
reproduction, a double
whammy.
A
few days after my son’s
question, I took him along
to an interview with a U.S.
Forest Service scientist in
an area where the bugs were
spreading, along Swan
Mountain Road, near a
favorite patch of edible
mushrooms scattered through
thin tufts of grass and pine
needles on the forest floor.
About half the trees were
already marked as dead by
their rust-colored needles,
and the rest were doomed.
It
was hot and windless. At one
point, the scientist asked
us to stop talking and
listen. After a few seconds,
we heard and felt a faint,
pulsing vibration—the sound,
she said, of millions of
beetles chewing through the
nutrient-carrying phloem
layer just beneath the bark.
The
damage was mostly invisible,
but it was happening
everywhere at once. The
researcher explained that
spring had come so early and
summer lasted so long that
the insects were breeding an
entire second generation
within the seasonal cycle,
something that had never
been recorded before the
1980s. That all but
guaranteed that the
remaining trees would be
overwhelmed, and soon after,
the mushroom patch would
disappear.
Our
sadness mirrored the
collective shock of
communities around the West
mourning the loss of forests
and landscapes that had
seemed timeless, with a huge
death toll of billions of
long-revered trees—piñon
pines, ponderosa, high
elevation spruce and fir
trees and even adaptable
aspens all succumbing to
climate-related
disturbances.
How
do changes in forests
affect the broader
landscape?
One
good example is a
beetle-caused die-off of
piñon pines in the
Southwest, also in the early
2000s. The pine nuts of the
piñon were an important food
source for Native American
tribes in the region for
thousands of years, and are
still culturally important
and have spiritual value.
But so many of the mature
seed-carrying trees died
that it became nearly
impossible for some people
to find them.
Major
changes in forests also
affect the land and how
water moves across it. When
trees die or burn, rain
falls on bare soil instead
of leaves and needles,
running off more quickly and
carrying sediment downhill.
Slopes once held together by
roots can loosen. In
mountain headwaters, those
changes can ripple into
rivers that supply farms,
towns and hydropower plants
far from forests.
Can
you tell me about the
recent study you covered
on European forests?
Forest
disturbance across Europe
could more than double by
the end of the century with
continued global warming,
according to the research,
which published in March.
The study showed how
different types of climate
impacts intensify each
other. It focused on
European forests, but there
are similar processes
happening everywhere around
the world.
It’s
a warning sign, along with a
lot of other recent
research, that forests and
trees, in general, are
struggling in a climate
that’s already 2.5 degrees
Fahrenheit warmer than the
average climate in which
these forests first started
growing.
The
study was interesting
because it used artificial
intelligence to analyze
forest landscapes at a very
detailed scale, down to
plots the size of a couple
of football fields. That
level of detail helped
researchers show in a
spatially realistic way how
the disturbances can
spread.
And
the conclusions are that, if
warming keeps up at the
current rate, there will be
widespread changes, with
more patchy forests, more
stands of younger trees,
some areas where trees will
be lost for the foreseeable
future, or where new types
of trees move in.
Is
there any way to prevent
this?
If
we stop burning fossil fuels
and heating the planet, we
can perhaps avoid some of
the worst-case endings of
massive, permanent forest
loss, or the loss of iconic
species like redwoods and
giant sequoias or Joshua
trees. And also, we should
stop cutting down older,
naturally growing forests
and try to protect the
forests that are left.
The
good news is that forests
have existed on Earth for
much, much longer than
humans, which means they’ve
survived some pretty extreme
climate cycles of warm and
cold. That means they will
most likely persist through
the human-caused warming
era. But exactly what kind
of trees will grow where,
and for how long, is
uncertain.
Postcard
From … Colorado
For
this week’s “Postcards
From,” Bob shared a photo
with his son from one of
their forest adventures in
Colorado.
“Trees
that my son climbed in the
early 2000s have since
succumbed to beetles,
drought and extreme heat,
like this centuries-old
Douglas fir. In the
background are stands of
lodgepole pines turning
brownish-orange after being
killed by mountain pine
beetles,” Bob said.
“This
is part of a group of
Douglas firs that have had
core samples taken to show
climate records going back a
few centuries.”
