Ore. September 8, 2010. The potential for outbreaks of spruce and
mountain pine beetles in western North America’s
forests is likely to increase significantly in the coming decades,
according to a study conducted by USDA Forest Service researchers
and their colleagues. Their findings, published in the September
issue of the journal BioScience, represent the first comprehensive
synthesis of the effects of climate change on bark beetles.
Native bark beetles are responsible for the death of billions of
coniferous trees across millions of acres of forests ranging from
Mexico to Alaska,” said Barbara Bentz, research entomologist
with the Forest Service’s Rocky
Mountain Research Station and lead author of the study. “Our study begins to explain
how their populations respond to the climatic changes being projected
by the Intergovernmental Panel on Climate Change.”
study, Bentz and her colleagues synthesized what is currently known
about the effects of climate change on several species of
bark beetles that cause extensive, landscape-scale tree mortality
in North America. They then used a combination of models to analyze
the likely response of and generate case studies for two specific
species—the spruce beetle and mountain pine beetle.
“Our models suggest that climatic changes on the order of what is
expected would increase the population success of both spruce beetle
and mountain pine beetle throughout much of their range, although
there is considerable variability,” said Chris Fettig, a
research entomologist with the Pacific Southwest Research Station
and a coauthor of the study. “Bark beetles are influenced
directly by shifts in temperature, which affect developmental timing
and temperature-induced mortality, and indirectly, through climatic
effects on the species associated with beetles and their host trees.”
effect the study detected is the likelihood, in a warming climate,
of a substantial increase in areas of spruce forest dominated by
spruce beetles that reproduce annually rather than every two years,
as is common today. Annual reproduction of the beetle can contribute
significantly to population growth and the occurrence of outbreaks.
In addition, the study’s models also helped to address
concerns about the potential for mountain pine beetles to expand
across forests of central Canada into the central and Eastern United
States. The researchers found that, without adaptation to warming
temperatures, the likelihood of this occurring is low to moderate
throughout this century.
Understanding how bark beetle populations will be affected under
different climate scenarios in different regions is key to developing
appropriate management strategies in North American forests,” Bentz
To read the study’s abstract online, visit http://caliber.ucpress.net/doi/abs/10.1525/bio.2010.60.8.6.
The study was a partnership among the Forest Service’s three
western research stations; the Western
Wildland Environmental Threat Assessment Center; the Canadian
Forest Service; and the University
of Idaho, Moscow.
The PNW Research Station is headquartered in Portland, Oregon.
It has 11 laboratories and centers located in Alaska, Oregon, and
Washington and about 425 employees.