A beetle about the length of a well-trimmed fingernail may be
challenging scientists' projections for global warming.
Forests store large amounts of carbon drawn from the atmosphere,
helping Earth keep cool. But an infestation of mountain pine beetles
is turning more than 144,000 square miles of woods in British
Columbia from a slight carbon absorber - or sink - to a net CO2
emitter. Canadian scientists unveiled projections Wednesday that
between 2000 and 2020, the forest will have lost 270 million tons of
carbon into the atmosphere.
The process has the potential to become a vicious cycle: As the
climate warms, it favors more severe outbreaks, and if severe
outbreaks increase, that leaves fewer trees to absorb carbon and
more emissions as dead trees decompose. Researchers say British
Columbia's problem highlights a growing threat that North American
forests, too, face from climate change.
"This is very important," acknowledges Tom Veblen, a geographer
at the University of Colorado at Boulder who is looking at the
interplay of climate change, insect infestations, and wildfires in
forests in the western United States. He notes that climate models
do not take this type of feedback into account when they gauge
temperature trajectories as human-related greenhouse-gas emissions
"It's been known for some time that insects are an important part
of the boreal-forest carbon cycle," says Werner Kruz, a scientist at
the National Resources Canada's Pacific Forestry Centre in Victoria,
British Columbia, who headed the modeling effort. But, he adds, the
failure to include bugs' cumulative effect in climate models could
be leading researchers to overestimate the amount of human-
generated CO2 forests can absorb.
British Columbia is deep into its worst infestation of mountain
pine beetles on record. Annual emissions from the worst year of
infestation come close to matching the average annual emissions from
all the forest fires the country experienced between 1959 and 1999,
researchers say. Over the 21-year period the projections cover,
emissions from the affected forests appear comparable to five years'
worth of emissions from Canada's entire transportation sector.
Canada's beetle problem highlights a threat North American
forests face from climate change, in addition to wildfires, logging,
mining, and other development activities, say researchers. By some
estimates, mountain pine beetles and their bark-burrowing cousins
infest some 50 million acres of forest, stretching from Alaska to
the southwestern US.
And the outbreak highlights the challenges resource managers face
as they try to preserve forest resilience in the face of a changing
climate and pressure to exploit timber and mineral resources.
Because the beetles stay burrowed underneath the bark, the only
known method to control infestations before they get out of hand is
to cut down the trees they've killed or the live trees they've
infected. It's an approach that raises the hackles of some
environmentalists and ecologists alike. …