can use to adapt to climate change. These strategies
include such steps as conducting vulnerability assessments, developing adaptation plans, and translating
these into a land management plan. “We’re trying to
be the nexus of what they can do” to adapt to climate
change, says Millar.
Unruly Ungulates.
USFS employees erect
an exclosure designed
to keep deer, elk, and
moose away from an
aspen-regeneration
area in Colorado.
Overpopulated deer
herds can impede
forest health by eating
young trees, which
ultimately reduces
forest diversity and
wildlife habitat.
Battling the Beetles
Climate change is largely to blame for the invasion
of beetles—both native and non-native—which are
killing forest trees, and occasionally urban trees,
across North America. Native bark beetle numbers
have risen because of warmer winters, which reduce
winter mortalities, and longer summers, which enable
extra breeding cycles. The beetles in turn exploit trees
stressed by drought, overcrowding, and extensive
wildfires. Bark beetle infestations have left millions of
acres of dead and dying trees across the Rocky Moun-
tain West, a crisis that recently prompted Agriculture
Secretary Vilsack to pledge an additional $40 million
to the USFS to combat the beetle (USDA 2009).
Among other damage:
• In 2008 Colorado officials predicted that the rapid
spread of the mountain pine beetle (Dendroctonus
ponderosae) would most likely destroy all of the
state’s mature lodgepole pine forests within three to
five years (Office of Governor Bill Ritter, Jr. 2008).
• Between 1996 and 2008, spruce beetles (
Dendroctonus rufipennis) destroyed 374,000 acres
of spruce trees in Colorado and 340,000 acres in
Wyoming (Stoddard 2009).
• Since its discovery in Michigan in 2002, the emerald
ash borer (Agrilus planipennis) has killed tens of
millions of ash trees in Michigan alone and tens of
millions more in 12 other states as well as Quebec
and Ontario in Canada (see emeraldashborer.info).
Credit: USFS
“When you put all these things together … it [reflects]
the impact of global climate change,” says Bruce
Hagen, a retired urban forester from the California
Department of Forestry.
In an attempt to control the mass destruction caused
by bark beetles across the West, researchers at Northern Arizona University tested the impact of digitally
altered recordings of the beetles own vocalizations.
They found that the beetles not only stopped burrowing and mating, they also stopped chewing on the pine
tree, suggesting that the acoustics of their calls could
make them uncomfortable enough to leave that environment (Northern Arizona University Press Release).
The hemlock woolly adelgid (Adelges tsugae) illustrates how much damage a non-native insect can do.
Introduced from Asia into the eastern U.S. in 1951,
the creature has caused a rapid decline in eastern
hemlock canopies across 17 states extending from
Maine to Georgia. This not only affects birds and
other species that depend on the tree canopy, but
also brook trout and other aquatic species that rely
on the cool temperatures of shaded streams.
Lacking effective natural enemies in the eastern U.S.,
this pest has been difficult to manage. In the 1990s,
however, USDA researchers began exploring the
biology and host range of five species of predaceous
beetles that might be deployed to suppress populations of the adelgid. For example, extensive research
has shown that Sasajiscymnus tsugae—a predatory
beetle discovered in Asia—may be effective in feeding
on the hemlock woolly adelgid as well as on other
adelgid species.
Another forest pest, the emerald ash borer, is
becoming a particular problem in urban forests,
where ash is a popular species. When the emerald ash borer was discovered in Butler County,
Pennsylvania in 2007, the state’s Department of
Agriculture imposed a quarantine prohibiting
the movement of any ash materials from the area
(Pennsylvania DCNR). Since then the pest has
been found in 10 other counties in the state. In
2008 the Pennsylvania Department of Conservation and Natural Resources (DCNR) signed on
to the National Detection Survey and also began
testing the effectiveness of “Purple Traps”—sticky
traps designed to attract the pest with compounds
that a distressed ash tree would release. “
Unfortunately, for every single pest we have to find
individual management tools,” says Houping Liu,
a forest entomologist with the DCNR. This makes
rapid eradication of new pests difficult.
