Communist
17th March 2010, 06:02
.
The Great Forest Die-Off (http://e360.yale.edu/content/feature.msp?id=2252)
What’s Killing the Great Forests of the
American West? A Frightening Phenomenon
Happening Across the Globe
By Jim Robbins
March 2010
Yale Environment
For many years, Diana Six, an entomologist at the University
of Montana, planned her field season for the same two to
three weeks in July. That's when her quarry - tiny, black,
mountain pine beetles - hatched from the tree they had just
killed and swarmed to a new one to start their life cycle
again.
Now, says Six, the field rules have changed. Instead of just
two weeks, the beetles fly continually from May until
October, attacking trees, burrowing in, and laying their eggs
for half the year. And that's not all. The beetles rarely
attacked immature trees; now they do so all the time. What's
more, colder temperatures once kept the beetles away from
high altitudes, yet now they swarm and kill trees on
mountaintops. And in some high places where the beetles had a
two-year life cycle because of cold temperatures, it's
decreased to one year.
Such shifts make it an exciting - and unsettling - time to be
an entomologist. The growing swath of dead lodgepole and
ponderosa pine forest is a grim omen, leaving Six - and many
other scientists and residents in the West - concerned that
as the climate continues to warm, these destructive changes
will intensify.
"A couple of degrees warmer could create multiple generations
a year," she said, as she chopped off a piece of bark on a
dead lodgepole pine to show the galleries of burrowing
larvae. "If that happens, I expect it would be a disaster for
all of our pine populations."
Across western North America, from Mexico to Alaska, forest
die-off is occurring on an extraordinary scale, unprecedented
in at least the last century-and-a-half - and perhaps much
longer. All told, the Rocky Mountains in Canada and the
United States have seen nearly 70,000 square miles of forest
- an area the size of Washington state - die since 2000. For
the most part, this massive die-off is being caused by
outbreaks of tree-killing insects, from the ips beetle in the
Southwest that has killed pinyon pine, to the spruce beetle,
fir beetle, and the major pest - the mountain pine beetle -
that has hammered forests in the north.
These large-scale forest deaths from beetle infestations are
likely a symptom of a bigger problem, according to
scientists: warming temperatures and increased stress, due to
a changing climate. Although western North America has been
hardest hit by insect infestations, sizeable areas of forest
in Australia, Russia, France, and other countries have
experienced die-offs, most of which appears to have been
caused by drought, high temperatures, or both.
One recent study collected reports of large-scale forest
mortality from around the world. Often, forest death is
patchy, and research is difficult because of the large areas
involved. But the paper, recently published in Forest Ecology
and Management, reported that in a 20,000-square-mile savanna
in Australia, nearly a third of the trees were dead. In
Russia, there was significant die-off within 9,400 square
miles of forest. Much of Siberia has warmed by several
degrees Fahrenheit in the past half-century, and hot, dry
conditions have led to extreme wildfire seasons in eight of
the last 10 years. Russian researchers also are concerned
that warmer, dryer conditions will lead to increased
outbreaks of the Siberian moth, which can destroy large
swaths of Russia's boreal forest.
While people in some places have the luxury to doubt whether
climate change is real, it's harder to be a doubter in the
Rocky Mountains. Glaciers in Glacier National Park and
elsewhere are shrinking, winters are warmer and shorter, and
the intensity of forest fires is increasing. But the most
obvious sign is the red and dead forests that carpet the
hills and mountains. They have transformed life in many parts
of the Rockies.
It has hit home for me on a personal level. Virtually every
one of the hundreds of old-growth ponderosa pines on the 15
acres of land where I live near Helena, Montana is dead, and
we are surrounded by a valley of dead and dying forest. Most
trees have been logged and taken to a pulp mill, where they
were turned into cardboard for boxes.
University of Montana ecologist Steve Running says warmer
temperatures in the Rockies bring spring earlier and fall
later, each by about a week, yet precipitation has remained
about the same. That translates into a drought, and stressed
trees are highly susceptible to beetle infestations.
Wintertime minimum temperatures in the 1950s, meanwhile,
ranged from 40 F to 50 F below zero. That's risen to the 30-
below range, and there are fewer days when minimums are
reached. It's not getting cold enough anymore to kill the
beetles, which over-winter in their larval stage and survive
the milder temperatures because they are filled with glycol,
a natural anti-freeze.
In addition, the past suppression of fire and the fact that
many Western trees are reaching the age at which beetles
target them - 80 to 100 years - are also factors in the
widespread loss of forests.
So the forests across the West are dying, in such large
numbers that U.S. Secretary of the Interior Ken Salazar
called it the West's Hurricane Katrina. In Colorado and
southern Wyoming, the U.S. Forest Service has created an
emergency management team to cut down dead trees around towns
and along roads and power lines. Forest Service campgrounds
and trails have been closed because of the hazard from dead
trees, and communities surrounded by dead forests have drawn
up emergency evacuation plans for residents.
Large-scale die-offs have occurred in the past. Mountain pine
beetles are native to the West and are part of the ecosystem.
Lodgepole forests regenerate through large-scale "stand
replacing events," which include fire and insects. The die-
offs now, though, are on a scale unprecedented since the West
was settled and are so big that they are having unusual
impacts on ecosystems. The whitebark pine, once largely
protected from the beetles because it grew at high altitudes
and was shielded by cold, is functionally extinct and may no
longer be able to feed grizzly bears and other species that
love its high-fat nut. In Mexico, bark beetles are beginning
to kill oyamel fir trees in a rare 139,000-acre biosphere
preserve where the majority of North America's monarch
butterflies travel each fall to spend the winter. So far,
about 100 acres in a core area of 33,000 acres have been
killed by bark beetles.
Tree-killing bugs aren't the only problem. In 2005 Colorado
researchers noticed that aspens were suddenly dying in large
numbers. That year they found 30,000 acres of dead aspen
forest. The next year there were 150,000 acres, and in 2008
it had soared to 553,000. The die-off is called Sudden Aspen
Death, or SAD. "It's growing at an exponential rate," said
Wayne Shepperd, who researches aspen for the Forest Service.
"It's pretty sobering when you see a whole mountainside or
whole drainage of aspen forest dead."
Groves at low elevations and facing south are dying fastest,
and scientists believe the cause is hotter temperatures and
drier weather. It's not only killing mature trees, but the
root mass as well. An aspen grove is the offspring of a large
single underground clonal mass, which sends up shoots. "The
whole organism is disappearing and it has profound
implications," Shepperd said. "When the roots die, groves
that are hundreds or thousands of years old aren't going to
be there anymore."
If the die-offs continue, the loss of the aspen trees would
be a blow to goshawks, songbirds, and a number of other
species that find food and refuge in the groves.
Perhaps more than anyone, Craig Allen is familiar with these
large-scale forest die-offs. A forest ecologist with the U.S.
Geological Survey's Jemez Mountain Field Station in New
Mexico, not only are his office and home surrounded by a
pinyon die-off, he also is the lead author of the paper -
with 19 other authors -published in Forest Ecology and
Management, which sought to document and begin to understand
what is happening to forests in North America and around the
world as the result of climate change.
Coming up with a definitive understanding at this point is
impossible, Allen says. Forests are complex, and
unfortunately, woefully understudied, and there isn't nearly
enough data to draw a conclusion about the reasons behind
forest die-offs globally. "There's huge information gaps and
uncertainties," says Allen.
What contributors were able to do in the paper is collect
anecdotal reports of broad-scale forest mortality from around
the world. "The point of this paper is to connect the dots,
at least the ones we can connect," says Allen. "We can't even
tell you for sure if there's more forest mortality. There's
not consistent monitoring."
In 2005 a strong El Nino caused a dramatic drought in the
Amazon. It killed forest across the region and is extremely
well documented because so many researchers had existing
plots there. "The heart of the biggest rainforest in the
world turned from a carbon sink to a carbon source," said
Allen. "If you have long-term drought you can bleed a lot
carbon into the atmosphere."
A lot of beetles can also turn vast tracks of forest from
carbon sinks to carbon sources. Take British Columbia, which
is ground zero for the mountain pine beetle infestation in
North America. Some 53,000 square miles of mature pine forest
is dead and the province is projected to lose 80 percent of
its mature trees by 2013. The second largest known die-off
there occurred in the 1980s and claimed just 2,300 square
miles. Bill Wilson - the province's director of Industry,
Trade and Economics Research - said he has flown in a plane
for hours over the province and seen nothing but dead forest
the entire time.
In 2008, so much of British Columbia's forests had died they
also went from being a net carbon sink to carbon source.
Diana Six works in Africa where she has seen other die-offs
first-hand. "In Africa where I work, suddenly whole hillsides
are dropping dead," she said. "It's happening so fast people
are in shock. It's a tragedy." Species include the quiver
tree, camel-thorn, and the giant euphorbia, a 30-foot-tall
succulent. The causes are not known, but the suspects are
hotter and drier weather, or shifting rainfall patterns.
All told, the paper that Allen co-authored describes 88 well-
documented forest die-offs around the world, going back as
far as the 1960s and 1970s, although most are in the 1990s
and 2000s.
If there was a way to predict die-offs, Allen said, land
managers could take preemptive action, such as mechanical
thinning or prescribed burning to increase the vigor of
forests.
What gives researchers pause is that many of these large die-
offs have occurred with minimal warming, in just a few years.
In the West, for example, the average temperature has warmed
on average 1.8 F over the past century. "This is before we
put two to four degrees centigrade (3.6 F to 7.2 F) into the
system," said Allen, referring to forecasts for warming by
the end of this century. Trees across the world are stressed
already from fragmentation, air pollution, and other
problems, he said. "I don't know how much stress the forests
of the world can take," said Allen.
© 2010 Yale Environment
.
The Great Forest Die-Off (http://e360.yale.edu/content/feature.msp?id=2252)
What’s Killing the Great Forests of the
American West? A Frightening Phenomenon
Happening Across the Globe
By Jim Robbins
March 2010
Yale Environment
For many years, Diana Six, an entomologist at the University
of Montana, planned her field season for the same two to
three weeks in July. That's when her quarry - tiny, black,
mountain pine beetles - hatched from the tree they had just
killed and swarmed to a new one to start their life cycle
again.
Now, says Six, the field rules have changed. Instead of just
two weeks, the beetles fly continually from May until
October, attacking trees, burrowing in, and laying their eggs
for half the year. And that's not all. The beetles rarely
attacked immature trees; now they do so all the time. What's
more, colder temperatures once kept the beetles away from
high altitudes, yet now they swarm and kill trees on
mountaintops. And in some high places where the beetles had a
two-year life cycle because of cold temperatures, it's
decreased to one year.
Such shifts make it an exciting - and unsettling - time to be
an entomologist. The growing swath of dead lodgepole and
ponderosa pine forest is a grim omen, leaving Six - and many
other scientists and residents in the West - concerned that
as the climate continues to warm, these destructive changes
will intensify.
"A couple of degrees warmer could create multiple generations
a year," she said, as she chopped off a piece of bark on a
dead lodgepole pine to show the galleries of burrowing
larvae. "If that happens, I expect it would be a disaster for
all of our pine populations."
Across western North America, from Mexico to Alaska, forest
die-off is occurring on an extraordinary scale, unprecedented
in at least the last century-and-a-half - and perhaps much
longer. All told, the Rocky Mountains in Canada and the
United States have seen nearly 70,000 square miles of forest
- an area the size of Washington state - die since 2000. For
the most part, this massive die-off is being caused by
outbreaks of tree-killing insects, from the ips beetle in the
Southwest that has killed pinyon pine, to the spruce beetle,
fir beetle, and the major pest - the mountain pine beetle -
that has hammered forests in the north.
These large-scale forest deaths from beetle infestations are
likely a symptom of a bigger problem, according to
scientists: warming temperatures and increased stress, due to
a changing climate. Although western North America has been
hardest hit by insect infestations, sizeable areas of forest
in Australia, Russia, France, and other countries have
experienced die-offs, most of which appears to have been
caused by drought, high temperatures, or both.
One recent study collected reports of large-scale forest
mortality from around the world. Often, forest death is
patchy, and research is difficult because of the large areas
involved. But the paper, recently published in Forest Ecology
and Management, reported that in a 20,000-square-mile savanna
in Australia, nearly a third of the trees were dead. In
Russia, there was significant die-off within 9,400 square
miles of forest. Much of Siberia has warmed by several
degrees Fahrenheit in the past half-century, and hot, dry
conditions have led to extreme wildfire seasons in eight of
the last 10 years. Russian researchers also are concerned
that warmer, dryer conditions will lead to increased
outbreaks of the Siberian moth, which can destroy large
swaths of Russia's boreal forest.
While people in some places have the luxury to doubt whether
climate change is real, it's harder to be a doubter in the
Rocky Mountains. Glaciers in Glacier National Park and
elsewhere are shrinking, winters are warmer and shorter, and
the intensity of forest fires is increasing. But the most
obvious sign is the red and dead forests that carpet the
hills and mountains. They have transformed life in many parts
of the Rockies.
It has hit home for me on a personal level. Virtually every
one of the hundreds of old-growth ponderosa pines on the 15
acres of land where I live near Helena, Montana is dead, and
we are surrounded by a valley of dead and dying forest. Most
trees have been logged and taken to a pulp mill, where they
were turned into cardboard for boxes.
University of Montana ecologist Steve Running says warmer
temperatures in the Rockies bring spring earlier and fall
later, each by about a week, yet precipitation has remained
about the same. That translates into a drought, and stressed
trees are highly susceptible to beetle infestations.
Wintertime minimum temperatures in the 1950s, meanwhile,
ranged from 40 F to 50 F below zero. That's risen to the 30-
below range, and there are fewer days when minimums are
reached. It's not getting cold enough anymore to kill the
beetles, which over-winter in their larval stage and survive
the milder temperatures because they are filled with glycol,
a natural anti-freeze.
In addition, the past suppression of fire and the fact that
many Western trees are reaching the age at which beetles
target them - 80 to 100 years - are also factors in the
widespread loss of forests.
So the forests across the West are dying, in such large
numbers that U.S. Secretary of the Interior Ken Salazar
called it the West's Hurricane Katrina. In Colorado and
southern Wyoming, the U.S. Forest Service has created an
emergency management team to cut down dead trees around towns
and along roads and power lines. Forest Service campgrounds
and trails have been closed because of the hazard from dead
trees, and communities surrounded by dead forests have drawn
up emergency evacuation plans for residents.
Large-scale die-offs have occurred in the past. Mountain pine
beetles are native to the West and are part of the ecosystem.
Lodgepole forests regenerate through large-scale "stand
replacing events," which include fire and insects. The die-
offs now, though, are on a scale unprecedented since the West
was settled and are so big that they are having unusual
impacts on ecosystems. The whitebark pine, once largely
protected from the beetles because it grew at high altitudes
and was shielded by cold, is functionally extinct and may no
longer be able to feed grizzly bears and other species that
love its high-fat nut. In Mexico, bark beetles are beginning
to kill oyamel fir trees in a rare 139,000-acre biosphere
preserve where the majority of North America's monarch
butterflies travel each fall to spend the winter. So far,
about 100 acres in a core area of 33,000 acres have been
killed by bark beetles.
Tree-killing bugs aren't the only problem. In 2005 Colorado
researchers noticed that aspens were suddenly dying in large
numbers. That year they found 30,000 acres of dead aspen
forest. The next year there were 150,000 acres, and in 2008
it had soared to 553,000. The die-off is called Sudden Aspen
Death, or SAD. "It's growing at an exponential rate," said
Wayne Shepperd, who researches aspen for the Forest Service.
"It's pretty sobering when you see a whole mountainside or
whole drainage of aspen forest dead."
Groves at low elevations and facing south are dying fastest,
and scientists believe the cause is hotter temperatures and
drier weather. It's not only killing mature trees, but the
root mass as well. An aspen grove is the offspring of a large
single underground clonal mass, which sends up shoots. "The
whole organism is disappearing and it has profound
implications," Shepperd said. "When the roots die, groves
that are hundreds or thousands of years old aren't going to
be there anymore."
If the die-offs continue, the loss of the aspen trees would
be a blow to goshawks, songbirds, and a number of other
species that find food and refuge in the groves.
Perhaps more than anyone, Craig Allen is familiar with these
large-scale forest die-offs. A forest ecologist with the U.S.
Geological Survey's Jemez Mountain Field Station in New
Mexico, not only are his office and home surrounded by a
pinyon die-off, he also is the lead author of the paper -
with 19 other authors -published in Forest Ecology and
Management, which sought to document and begin to understand
what is happening to forests in North America and around the
world as the result of climate change.
Coming up with a definitive understanding at this point is
impossible, Allen says. Forests are complex, and
unfortunately, woefully understudied, and there isn't nearly
enough data to draw a conclusion about the reasons behind
forest die-offs globally. "There's huge information gaps and
uncertainties," says Allen.
What contributors were able to do in the paper is collect
anecdotal reports of broad-scale forest mortality from around
the world. "The point of this paper is to connect the dots,
at least the ones we can connect," says Allen. "We can't even
tell you for sure if there's more forest mortality. There's
not consistent monitoring."
In 2005 a strong El Nino caused a dramatic drought in the
Amazon. It killed forest across the region and is extremely
well documented because so many researchers had existing
plots there. "The heart of the biggest rainforest in the
world turned from a carbon sink to a carbon source," said
Allen. "If you have long-term drought you can bleed a lot
carbon into the atmosphere."
A lot of beetles can also turn vast tracks of forest from
carbon sinks to carbon sources. Take British Columbia, which
is ground zero for the mountain pine beetle infestation in
North America. Some 53,000 square miles of mature pine forest
is dead and the province is projected to lose 80 percent of
its mature trees by 2013. The second largest known die-off
there occurred in the 1980s and claimed just 2,300 square
miles. Bill Wilson - the province's director of Industry,
Trade and Economics Research - said he has flown in a plane
for hours over the province and seen nothing but dead forest
the entire time.
In 2008, so much of British Columbia's forests had died they
also went from being a net carbon sink to carbon source.
Diana Six works in Africa where she has seen other die-offs
first-hand. "In Africa where I work, suddenly whole hillsides
are dropping dead," she said. "It's happening so fast people
are in shock. It's a tragedy." Species include the quiver
tree, camel-thorn, and the giant euphorbia, a 30-foot-tall
succulent. The causes are not known, but the suspects are
hotter and drier weather, or shifting rainfall patterns.
All told, the paper that Allen co-authored describes 88 well-
documented forest die-offs around the world, going back as
far as the 1960s and 1970s, although most are in the 1990s
and 2000s.
If there was a way to predict die-offs, Allen said, land
managers could take preemptive action, such as mechanical
thinning or prescribed burning to increase the vigor of
forests.
What gives researchers pause is that many of these large die-
offs have occurred with minimal warming, in just a few years.
In the West, for example, the average temperature has warmed
on average 1.8 F over the past century. "This is before we
put two to four degrees centigrade (3.6 F to 7.2 F) into the
system," said Allen, referring to forecasts for warming by
the end of this century. Trees across the world are stressed
already from fragmentation, air pollution, and other
problems, he said. "I don't know how much stress the forests
of the world can take," said Allen.
© 2010 Yale Environment
.