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By: Luke deBarathy Advisor: Dr. Liv Haselbach
ABSTRACT:
The mountain pine beetle (MPB) epidemic is one of the most
devastating insect outbreak since the
great locust swarms of the 1870s and is an environmental
disaster comparable to the dust bowl of the
1930s. The typical state of many North American pine forests --
mature, homogeneous, even-aged, and
dense -- combine into volatile environmental conditions primed
for a MPB population explosion. The
unusually warm and dry climate of the past couple decades has
fueled the beetles reproduction. The
resulting outbreaks have engulfed millions of acres of pine
forests from southern California to Alaska.
The aftermath has left billions of dead trees. If the trees are
not harvested, they will eventually
become a carbon source releasing CO2 back into the air either
rapidly through forest fire or slowly through
decay. Canadas Pacific Forestry Center has conducted studies
revealing that the magnitude of the beetle
disturbance is great enough to completely reverse the carbon
cycle of the forest. Furthermore, a study from
the University of Idaho estimates that infested stands will take
a generation to regain their living biomass
and the average stand will take over a century for its carbon
flux to become a net sink again. Carbon
emissions from forest fires are also expected to dramatically
increase in correlation with the beetle-kill.
Limiting the impact of the MPBs carbon footprint will require
proactive forest management that
emphasizes both economic benefit and forest health. Harvesting
beetle-kill trees for lumber, pulp, and other
commercial products permanently sequesters the carbon in the
wood. Furthermore, bio-mass from beetle-
kill can be utilized for energy production as a substitute for
fossil fuels. In a time of high unemployment
and recession, this could be at least a short term boom for many
existing and new businesses. Replanting
landscapes that are more biologically diverse will reduce the
likelihood of future epidemics and
simultaneously accelerate the forests carbon offset
potential.
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INTRODUCTION: QUANTIFYING THE NATURAL DISASTER
Butte Montana was once known as the Richest Hill on Earth
boasting the largest open pit copper
mine in North America. In 1983 the Berkeley Pit, which can be
seen in Figure 1, closed and shortly
thereafter Butte received a more infamous moniker: the largest
Superfund site in the country (Everett,
n.d.). Surprisingly, cleaning up the contamination and pollution
from past copper mining and smelting
activities is not the greatest environmental crisis that
concerns the "Mining City."
Figure 1: Butte Montana. The Berkeley Pit shadowed by the East
Ridge's pine forests
Over the past 15 years, the residents of Butte have watched the
slow motion death of most of the
scenic pine forests that surround the city. For hundreds of
miles in every direction trees have been turning
from a lush green to an ominous red and then to a haunting gray.
The stages of attack are exemplified in
Figure 4. A good comparison of the forests surrounding Butte's
Lady of the Rockies monument between
1991 and 2011 is shown in Figure 2. Butte is at the epicenter of
a natural disaster so vast that it threatens
ecological, social, and economic upheaval for both the United
States and Canada. The culprit for the
unprecedented forest die-off is an insect no larger than a grain
of rice, the mountain pine beetle (MPB)
(Leatherman, Aguayo, & Mehall, 2007).
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Figure 2: The Lady of the Rockies. Left 1992, Right 2011.
Between 1996 and 2011, MPB outbreaks have spread from southern
California to Alaska infecting
millions of acres of forest in the western United States and
Canada (Malhi, 2002). Most pines found in
North America are suitable hosts for the mountain pine beetle
(Logan, 2001), and the mortality rates for
mature pine trees within an infested area often exceed 80%
(Kurz, 2008). The epidemic continues to
proliferate at an alarming rate. It has reached central Alberta
where the lodgepole pine forests of the west
converge with jack pine forests that stretch east all the way to
the Atlantic Ocean. As soon as the mountain
pine beetle infests the jack pine forests, the devastation is
expected to spread rapidly across Canada and
southward through the United States (Gorte, 2009). The jack pine
is more susceptible to infestation because
it has not evolved the defenses to resist and survive beetle
attacks that the lodgepole pine has developed
(Gorte, 2009). The likely consequence of this scenario is a mass
die-off of continental scale. Note from
Figure 3 that once the beetles reach the Great Lakes, they can
infest the white pine forests on the East Coast
and spread through the yellow pine forests that cover the
southern states (Gorte, 2009).
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Figure 3: Mountain Pine Beetle Distribution Map.
CULTIVATING THE CRISES
Although bark beetle infestations are a regular force of natural
change in forested ecosystems, the
current outbreak has burgeoned into the largest and most severe
in recorded history (U.S. Forest Service,
2011). Several conditions have contributed to the extreme scale
of the current epidemic. Foremost, the
current generation of forests that characterizes the western
United States and Canada are ideal hosts for the
beetle because they are mature, homogeneous, and even-aged
largely due to a combination of widespread
severe wildfires (Logan, 2001) and large scale, intense logging
that occurred at the turn of the 19th century
(U.S. Forest Service, 2011).
In the 20th century, the Forest Service focused on suppressing
wildfire leading to unnaturally dense
forest conditions. Moreover, compliance with an ever expanding
bureaucracy and onerous environmental
regulations has made logging and thinning evermore protracted
and cost prohibitive (Willms, 2010). Trees
growing in an overcrowded environment must compete for resources
causing the trees to become stressed
and more vulnerable to infestation (U.S. Forest Service, 2011).
Likewise, drought weakens the ability of
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trees to resist and survive an infestation. Many of the regions
hardest hit by the bark beetle conquest have
correspondingly experienced drought conditions (U.S. Forest
Service, 2011).
Figure 4: Stages of Attack.
THE CLIMATE FOR THE BEETLES PERFECT STORM
In addition to shifts in precipitation patterns and associated
drought, climate conditions over the
past 20 years have been ideal for the beetles reproduction. The
mountain pine beetle is a seasonally adapted
univoltine (has a one year life cycle), and its reproductive
success is very sensitive to temperature (Bentz,
2010). The complete lifecycle of the mountain pine beetle is
illustrated in Figure 6. The life cycle of the
beetle begins in the late summer when their eggs hatch about two
weeks after being laid (called oviposition)
(Logan, 2001). The larvae begin feeding on the innermost bark
layer, called the phloem, of the pine tree
and begin producing glycerol, a natural antifreeze that allows
the larvae to survive extreme winter
temperatures (Leatherman, Aguayo, & Mehall, 2007). The
beetle larvae are particularly vulnerable to late
summer frosts prior to producing ample glycerol. However, once
the larvae are established for winter,
temperatures must drop to -30F for five consecutive days to
significantly reduce the beetles population
(Logan, 2001).
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The larvae continue feeding throughout winter creating tunnels
through the trees phloem.
Eventually these tunnels, shown in Figure 5, cut off the
exchange of nutrients between the trees roots and
its crown killing the tree (Logan, 2001).
Figure 5: Mountain Pine Beetle Galleries.
The larvae pupate in the early summer and the emergence of adult
beetles begins in June and
continues through September with the majority of beetles exiting
their host trees in late July (lodgepole
pine) and mid-August (ponderosa pine) (Leatherman, Aguayo, &
Mehall, 2007). Cold and wet weather
jeopardizes beetles that emerge too early. The female beetles
take flight and typically seek trees with trunk
diameters larger than 4 inches (U.S. Forest Service, 2011)
because mature trees have a thicker phloem that
is better able to provide the larvae with ample sustenance
(Leatherman, Aguayo, & Mehall, 2007).
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Figure 6: The Mountain Pine Beetle Lifecycle (Wyoming Forestry
Division ).
A noteworthy aspect of this cycle is the transmission of
blue-stain fungi between host trees. Spores
affix to the bodies of the adult beetles as they emerge from
their domicile and are introduced to the new
host tree upon attack. The fungus stains the sapwood a distinct
blue-gray color, and clogs the water
transport systems of the tree which weakens the tree and
ultimately assists the beetle in symbiotically killing
the tree (Leatherman, Aguayo, & Mehall, 2007). Once a tree
is infested, there is nothing economically
viable that can be done to save that tree (Gorte, 2009). As
shown in Figure 7, the blue-stain fungus alters
the appearance of the wood, but it does not affect the
structural properties of the wood (Gorte, 2009).
Because the fungus absorbs and traps moisture, it does
accelerate decomposition of the wood. Beetle-killed
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trees can be harvested for lumber for at least 5 years after
mortality and up to 18 years depending on the
circumstances (Gorte, 2009).
Figure 7: Blue Wood.
The dispersion range of the mountain pine beetle is typically
less than a mile before the female
beetles find a suitable host tree. Although the beetle is a weak
flyer, experiments performed by John
Byers, a professor at the Swedish University of Agricultural
Sciences, estimates that the beetle is capable
of taking advantage of wind currents to travel distances up to
28 miles (Byers, 2000). When the female
finds a suitable tree, she bores through its bark creating an
egg gallery and releases aggregating
pheromones which attract males for mating as well as other
females who attack the area in mass (Logan,
2001). This is the primary reason homogeneous even-aged stands
are particularly vulnerable to bark beetle
outbreaks. After mating, the female typically lays about 75 eggs
(Leatherman, Aguayo, & Mehall, 2007).
If the offspring are not exposed to lethally cold weather
conditions, enough beetles can emerge from an
infested tree to kill multiple trees the following year (Logan,
2001).
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SINKING FORESTS AND CHANGING THE CARBON CYCLE
Global warming alarmists regard the mountain pine beetle
outbreak as a direct consequence of
anthropogenic induced climate change and a harbinger of
impending global ecological disaster correlated
with emissions from the combustion of fossil fuels. Arguments
linking the beetle outbreak and global
warming are routinely made by advocacy groups lobbying for
policies aimed at reducing greenhouse gas
emissions. Perhaps, the most influential of which is the
Alliance for Climate Protection (ACP). ACP was
founded by former Vice President Al Gore in 2006 and boasts over
5 million members and has hundreds
of millions of dollars at its disposal (Climate Reality Project,
2012). In 2008, ACP launched the 34 million
dollar RePower America Campaign with the objective of gaining
support for climate change legislation
(Repower America, 2012).
At an event held at Mount Rushmore, Repower America spokesman,
Matt McGovern, opened his
oration with the following statement, The effects of global
warming can be seen in the growing splotches
of brown trees scattered throughout the otherwise green sheen of
the Black Hills National Forest.
Shadowed by the monuments bust of Teddy Roosevelt, forefather of
American wildlife conservation, Mr.
McGovern announced, The plague of mountain pine beetle
infestations in forests across the American
West is happening on a scale that is symptomatic of a world-wide
climate-change problem. The beetles
thrive in a warmer climate, which doesnt provide the degree of
temperature lows needed to kill the bugs.
An overwhelming majority of scientists agree that those
environmental conditions are tied to warming in
the earths atmosphere caused by increased CO2 emissions from a
variety of man-made sources, including
coal-fired electrical plants. He then went on to rally for
support for the reform package backed by
President Obama and congressional Democratic leaders that would
tax emissions from carbon producers
such as coal plants and promote alternative energy production
such as wind and solar (Woster, 2009).
Dave Thom, a natural resources specialist with the Black Hills
National Forest, was asked to react
to McGoverns speech for a Rapid City Journal news article
covering the event. Mr. Thom emphasized the
dense and mature biogeographics of the forest as the primary
causation fueling the beetle conflagration and
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downplayed linking the outbreak with manmade global warming
saying, [bark beetle outbreaks] can
happen regardless of a few degrees of change in temperature
measured on a global scale. He then
explained the necessity for the U.S. Forest Service to continue
thinning the forests because, The
management work we do year to year has a greater effect reducing
infestation than climate changes that
occur over decades (Woster, 2009). A comprehensive scientific
explanation that answers how a 0.59 C
increase in average global temperatures between 1900 and 2011
(National Aeronautics and Space
Administration Goddard Institute for Space Studies, 2012) is the
critical catalyst responsible for the
outbreaks unprecedented size and scale could not be found for
this literature review. While the beetle
epidemic is the largest in recorded history, the fact remains
that the regular low temperatures needed to
suppress the beetles conquest also have not occurred in recorded
history with the exception of perhaps the
northern most reaches of the outbreak.
The degree to which global warming has influenced the current
beetle epidemic is controversial
and uncertain; however, the outbreak certainly reduces the
effectiveness of the infected forest to act as a
carbon sink because the billions of trees killed by beetles
cease consuming CO2 from the atmosphere.
Moreover, these trees eventually become a carbon source
releasing carbon back into the air either rapidly
through forest fire or slowly through decay (Ryan, 2008).
W.A. Kurz, a senior research scientist with Canadas Pacific
Forestry Center as well as Coordinator
of the Carbon Task Force of the International Union of Forest
Research Organizations, is the formost expert
on insect disturbances in forest ecosystems and on the effects
such disturbances have on the carbon cycle.
W.A. Kurz published a startling study in Nature modeling the
carbon cycle of a sample area located in the
south-central region of British Columbia that has been
overwhelmed by the beetle outbreak. A map and
photo of the sample area is shown in Figure 8. The model
accounts for annual tree growth, litter-fall,
turnover and decay, and explicitly simulates beetle caused
mortality over the sample area. The studys data
reveals the outbreak turned the forestland from a net carbon
sink to a large carbon source both during and
immediately after the outbreak. The net carbon dioxide
equivalent sink loss caused by the beetle epidemic
over 21 years is estimated at 990 Mt CO2e (Kurz W. A., 2008).
For comparison, the anthropogenic
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emissions of greenhouse gases from all of Canadian sources in
2005 was about 747 Mt CO2e (Government
of Canada, 2007), and average emissions from forest fires in all
of Canada are approximately 162 Mt CO2e
per year (Amiro, 2001).
Figure 8: Sample Area of Kurz's Research [8].
E.M. Pfeifer and Jeffrey Hicke, forestry professors at the
University of Idaho, headed a study
measuring aboveground tree stocks and modeling carbon fluxes
following a bark beetle outbreak. Their
findings corroborate and augment the conclusions from the Nature
article. The study estimates that stands
attacked by beetles take 7 to 25 years to regain their original
living biomass. As expected, stands with the
highest mortality rates take the longest to regenerate. However,
even after the stand has ostensibly
recovered from the infestation, it continues to suffer a long
term drop in the rate that it metabolizes and
sequesters carbon dioxide. Affected stands on average would take
over a century for their carbon flux to
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become a net sink again (Byers, 2000). If left to natural
cycles, the millions of acres of forestland affected
by the beetle will remain carbon sources until the 22nd
century.
FIRE IMPACTS
Forest fires conflate and compound the carbon footprint of the
bark beetle. Net carbon emissions
from forest fires are expected to escalate dramatically over the
next several years due to additional fire
hazard correlated with the 30 billion dead and dying trees that
have been girdled and killed by the mountain
pine beetle. The basic ecologic cycle of the lodgepole pine
forest is dependent on the inter-relationship
between beetle-caused mortality and subsequent fire (Logan,
2001). The mountain pine beetle acts as
natures forest manager by attacking stands of mature pines and
leaving stands of saplings. A fire replacing
stand usually occurs within 15 years following an outbreak
(Gorte, 2009). If forest fires do not occur, more
shade tolerant species such as spruce and fir eventually replace
the pine stand because the serotinous cones
of the pine require heat from a fire to release its seeds
(Gorte, 2009).
Dead needles provide a highly combustible source of fine fuels
and the dry and decaying trees
provide a source of ignition maintenance for lightning strikes.
Once ignited, decaying logs are capable of
smoldering for weeks until hot, windy, and dry weather
conditions incite a firestorm (Logan, 2001). Years
of strategic fire suppression has exacerbated the volatile
situation on the ground. The forest floor contains
nearly double the biomass compared to the natural conditions
prior to European settlement (USDA Forest
Service, 2011). This increases the risk of a large-scale fire
that could sterilize the soil and delay the
regeneration of the forest for decades. This in turn increases
erosion and pollution of our water sources
(Logan, 2001). Figure 9 is a photo of a forest where the soil
has been sterilized by a recent wildfire.
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Figure 9: Sterilized Soil by Wildfire.
A study on fire behavior in beetle-killed lodgepole pine forests
found that both the fireline intensity
and the rate of fire spread are higher in beetle-killed stands
in comparison to endemic stands (Page &
Jenkins, 2007). Dr. Brian Amiro, professor at the University of
Manitoba and Research Scientist with the
Canadian Forest Service, led an investigation on Canadas
ever-growing forest fire hazard. The studys
report forecasts that emissions due to forest fire will likely
double from the current levels to 313 Mt CO2e
per year as result of disturbances from insects, exceedingly
dense forest conditions, and drought related to
climate change (Amiro, Cantin, Flannigan, & Groot, 2009). If
this prediction is accurate, annual carbon
dioxide equivalent emissions from forest fires will be grow to
about 1.5 times that produced by the entire
Canadian transportation sector in 2005 (200 Mt CO2e) (Government
of Canada, 2007).
Those who have lived in areas prone to forest fires are not
surprised by this statistic. The worst
Los Angeles smog is marginal in comparison to the air pollution
during fire season in Butte Montana, where
smoke and particulate matter is often so thick ones vision is
limited to less than a mile and average people
are advised to where protective masks and respirators while
outdoors (Duganz, 2006). Those with asthma,
emphysema, and heart conditions experience aggravated symptoms
and are at advanced risk for
complications and often spend the late summer months in agony
(Fowler, 2003). People, usually the elderly,
with severe respiratory or pulmonary conditions must be
quarantined into hospice facilities with particle
filtration systems (Missoula City-County Health Department,
2010).
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CONCLUSION
The mountain pine beetle has caused dramatic changes to the
ecosystem. From the looks of the
Forest Services internal review regarding its response to the
outbreak, it appears the beetle is also
responsible for dramatic changes in the Forest Services
allocation of resources, evaluation of priorities,
and management philosophy (USDA Forest Service, 2011). In the
past, the majority of the Forest Services
resources were dedicated to aggressively fighting forest fires
to protect living forests. Now, the Forest
Services top priority is focusing on reestablishment of the
millions of acres of dead forests (USDA Forest
Service, 2011). Forest managers are determined to learn from
past mistakes by employing forestry practices
to create more biologically diverse forest landscapes that will
reduce the likelihood of future epidemics and
the severity of the consequences when epidemics occur (U.S.
Forest Service, 2011). This was not merely
a mountain pine beetle epidemic, but also an epidemic of
pine.
The studies conducted by Dr. Kurz, Dr. Pfeifer, Dr. Hicke, and
others on the mountain pine beetle
epidemic confirm that disturbances are principle drivers of the
forest carbon budget. Their work also serves
as a microcosm highlighting the vital role forests play in the
global carbon cycle, and the potential benefits
that good forest management practices can have in offsetting
emissions from anthropogenic fossil fuel
combustion. Harvesting beetle-kill trees for lumber, pulp, and
other commercial products permanently
sequesters the carbon in the wood. In addition, material
substitutes to wood such as steel, plastic, and
concrete require more energy to produce because they are the
products of mining, possessing, and
manufacturing (Ryan, 2008). This translates to more energy being
used and greenhouse gases being
emitted. Furthermore, bio-mass from beetle-kill can be utilized
for energy production as a substitute for
fossil fuels. Burning biomass, a renewable resource, generally
means that fossil fuel will not be burned
(Ryan, 2008).
Given the vast amount of carbon sequestered within the
beetle-kill trees, one would expect that
environmental and political organizations concerned about global
warming, such as the aforementioned
Alliance for Climate Protection, are boisterously advocating for
harvesting and utilizing these trees. While
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the ACP found it useful to point out the beetle-kill trees in
order to advance its carbon tax agenda, it is silent
on using the beetle-kill to prevent the advance of the carbon
positive feedback loop created if the trees are
left to rot or burn (Climate Reality Project, 2012). Seems when
the carbon problem is disassociated from
a tax solution, the carbon loses its value and is no longer a
worthwhile issue for most environmentalists
concerned about global warming. One is probably wasting his
carbon-laden breath trying to convince self-
described tree huggers to embrace logging in any capacity.
Perhaps the best way to increase demand of beetle-kill products
is to encourage wood certification
organizations to give preferential treatment to forest lands
that have suffered catastrophic forest loss due to
extraordinary disturbances from not just insects but also fire
and disease. After all, prioritizing dead and
diseased trees not only decreases demand for healthy trees on
virgin lands, but also encourages active forest
stewardship in areas that need it most. The Forest Stewardship
Council (FSC), the Sustainable Forest
Initiative (SFI), and the Program for the Endorsement of Forest
Certification (PEFC) all aim to ensure
forests are managed in a sustainable and ecologically sound
manner and thus limit the quantity of wood
that can be harvested for a given area. Dead trees in areas
impacted by large disturbances simply should
not be counted in the same manner as healthy trees with respect
to harvesting restrictions. If beetle-kill
could receive an addendum for certification, blue wood would in
turn be considered a preferable material
in the U.S. Green Building Council's green rating system, LEED,
as well as in the International Code
Council's 2012 Green Construction Code thereby gaining market
share as a material among green conscious
consumers and builders.
While the beetle tsunami has been devastating, the tragedy will
be compounded if the wood of the
dead trees left in its wake are wasted. The commercial lifespan
of beetle-kill pine trees is finite and the
wood begins losing its marketability after 5 years (Gorte,
2009). This gives only a small window of time
through which salvaging the near endless supply of beetle-kill
trees remains feasible. In a time of high
unemployment and recession, this could be at least a short term
boom for many existing and new businesses.
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REFERENCES
1. Bentz, Barbara. 2008. Western U.S. Bark Beetles and Climate
Change. (May 20, 2008). U.S.
Department of Agriculture, Forest Service, Climate Change
Resource
Center. http://www.fs.fed.us/ccrc/topics/bark-beetles.shtml
2. Ryan, Michael G. 2008. Forests and Carbon Storage. (June 04,
2008). U.S. Department of
Agriculture, Forest Service, Climate Change Resource
Center. http://www.fs.fed.us/ccrc/topics/carbon.shtml
3. GISS Surface Temperature Analysis (GISTEMP) National
Aeronautics and Space Administration
Goddard Institute for Space Studies. 2/14/2012,
http://data.giss.nasa.gov/gistemp/
4. U.S. Forest Service. Western Bark Beetle Strategy. (July 11,
2011).
http://www.fs.usda.gov/main/barkbeetle/home
5. Ross W. Gorte, Cong. Research Serv., R40203, Mountain Pine
Beetles and Forest Destruction:
Effects, Responses, and Relationship to Climate Change 1
(2009).
6. Willms, J. David; The Mountain Pine Beetle: How Forest
Mismanagement And A Flawed Regulatory
Structure Contributed To An Uncontrollable Epidemic
7. Wesley Page & Michael J. Jenkins, Predicted Fire behavior
in Selected Mountain Pine beetle-Infested
lodgepole Pine, 53 foreSt ScI. 662, 673 (2007), available at
http://www.wy.blm.gov/
fireuse/pubs/FireBehavior-PineBeetle.pdf.
8. Kurz, W. A., Dymond, C. C., Stinson, G., Rampley, G. J.,
Neilson, E. T., Carroll, A. L., Safranyik,
L., ... Ebata, T. (April 24, 2008). Mountain pine beetle and
forest carbon feedback to climate
change. Nature, 452, 7190, 987-990
9. Jesse A. Logan and James A. Powell, Ecological Consequences
of Climate Change Altered Forest
Insect Disturbance Regimes, Climate Change in Western North
America: Evidence and
Environmental Effects , Univ. of Utah Press, Salt Lake City, UT,
in press.Bottom of Form
10. Everett, George. Only In Butte. 2003. 1/16/2012
http://www.butteamerica.com/oib.htm
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11. Pfeifer, E. M., Hicke, J. A., & Meddens, A. J. H.
(January 01, 2011). Observations and modeling of
aboveground tree carbon stocks and fluxes following a bark
beetle outbreak in the western United
States.Global Change Biology, 17, 1, 339-350.
12. D.A. Leatherman, I. Aguayo & T.M. Mehall, Mountain Pine
Beetle, Trees & Shrubs no.5.528 (Colo.
State Univ. Extension, Fort Collins, Colo.), Apr. 2007,
available at
http://www.ext.colostate.edu/pubs/insect/05528.pdf.
13. Byers, J. A. (January 01, 2000). Wind-aided dispersal of
simulated bark beetles flying through
forests. Ecological Modelling, 125, 2, 231 Byers, John A, 1999,
Swedish University of Agricultural
Sciences, Plant Protection, S-230 53, accepted 9 August 1999,
Wind-aided dispersal of simulated
bark beetles flying through forests
14. Logan, J. A., & Powell, J. A. (January 01, 2001).
Articles - Features - Ghost Forest, Global Warming,
and the Mountain Pine Beetle (Coleoptera: Scolytidae) -
Outbreaks of the mountain pine beetle are an
important part of ecological cycles in western pine forests and
have provided researchers with
insights into both the beetle's and the forest's evolutionary
adaptability. American Entomologist, 47, 3,
160.
15. Kurz, W. A., Stinson, G., & Rampley, G. (January 01,
2008). Could increased boreal forest
ecosystem productivity offset carbon losses from increased
disturbances?. Philosophical Transactions
of the Royal Society of London. Series B, Biological Sciences,
363, 1501, 2261.
16. Review of the Forest Service response--the bark beetle
outbreak in northern Colorado and southern
Wyoming. (2011). S.l.: USDA Forest Service, Rocky Mountain
Region and Rocky Mountain
Research Station
17. Amiro, B.D., A. Cantin, M.D. Flannigan, and W.J. de Groot,
NRC Research Press, Future emissions
from Canadian boreal forest fires
18. Amiro, B. D., Todd, J. B., Wotton, B. M., Logan, K. A.,
Flannigan, M. D., Stocks, B. J., Mason, J. A.,
... Hirsch, K. G. (January 01, 2001). Direct carbon emissions
from Canadian forest fires, 1959-
1999. Canadian Journal of Forest Research. Journal Canadien De
La Recherche Forestiere, 31, 3,
512
19. Environment Canada. 2007. Canadas 2005 greenhouse gas
inventory: a summary of trends.
Available from
http://www.ec.gc.ca/pdb/ghg/inventory_report/2005/2005summary_e.cfm.
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20. Podur, J., Martell, D.L., and Knight, K. 2002. Statistical
quality control analysis of forest fire activity
in Canada. Can. J. For. Res. 32: 195205.
doi:10.1139/x01-183.
21. Stocks, B.J., Mason, J.A., Todd, J.B., Bosch, E.M., Wotton,
B.M., Amiro, B.D., Flannigan, M.D.,
Hirsch, K.G., Logan, K.A., Martell, D.L., and Skinner, W.R.
2002. Large forest fires in
Canada,19591997. J. Geophys. Res. 108.
doi:10.1029/2001JD000484.
22. U.S. Environmental Protection Agency. 2007. Inventory of
U.S. Greenhouse Gas Emissions and
Sinks: 19902005. Washington, DC: U.S. Environmental Protection
Agency.
23. Woster, Kevin, Rapid City Journal, Pine beetle, global
warming connection debated 9/19/2009
24. Climate Reality Project, 1/24/2012,
http://climaterealityproject.org/
25. Repower America, 1/24/2012,
http://www.repoweramerica.org/
26. Malhi, Y., Meir, P., & Brown, S. (August 15, 2002).
Forests, carbon and global
climate. Philosophical Transactions: Mathematical, Physical
& Engineering Sciences, 360, 1797,
1567-1591
27. Duganz, Pat, The Montana Standard, Smoke Can Be Harmful,
8/16/2006
http://mtstandard.com/news/local/smoke-can-be-harmful/article_d8fefd04-361c-58ed-8a48-
b298793a9d65.html
28. Fowler, Cynthia T. , Journal of Ecological Anthropology
Volume 7 2003, p39 to p. 63, Human
Health Impacts of Forest Fires in the Southern United States: A
Literature Review
29. Wildfire smoke: A guide for public health officials.
Missoula: Missoula City-County Health
Department. 2001
30. Illustration taken from Wyoming Forestry Division Website:
http://slf-
web.state.wy.us/oldsite/forestry/healthassist2.aspx