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This article is one of a series exploring the devastating issues surround mountain pine beetle infestation, in particular, in the Colorado Rocky Mountains.
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Colorado Mountain Pine Beetle Infestation: Causes, Consequences, and Cures
Article Two - August 2011, written for an Environmental Management course through Harvard University
© Allison Frederick, All Rights Reserved, for comments & questions, email info at greenideaprotection.com
Introduction (as previously presented)
The Mountain Pine Beetle infestation in Colorado’s mountains has killed more than 1.5 million trees in the past decade adversely impacting Colorado’s ecology, economy, and aesthetic. The consequences of the infestation shall be extensive, long-term, and costly in many respects. This review explores the etiology of the infestation, responses to the infestation, environmental and economic impacts, and offers a multi-pronged approach for present and future management. continue reading first article...
Article 2 - How did the pine bettle infestation in the Rocky Mountains begin?
The infestation is commonly referred to in both scientific literature and the media as being caused by the mountain pine beetle. However, the damage to the pine forests is not actually caused by the MPBs themselves, but by the fungi spores living on the beetle’s body. The complex interaction between the mountain pine beetle and the fungi spore is an example of a small microcosmic relationship exerting large scale impact on a larger ecosystem. This example hints at the difficulties of not only identifying all the contributing factors of the pine beetle epidemic, but trying to sustainably manage the situation.
How did the current infestation progress from a relatively benign level to a devastating epidemic? The cause of the current MPB epidemic, like any epidemic, is multi-faceted (Figure 2). This epidemic appears to be the result of a combination of both natural weather phenomena creating unfavorable conditions for Colorado forests and the result of well-intentioned, but perhaps short-sighted, human intervention with unanticipated consequences.
Etiology of the Infestation
The first contributing factor cause appears to be natural. A four-year Colorado drought, beginning in 1998, is partially responsible for the waning health of the lodgepole pine stands making them increasingly susceptible to MPB infestation. The drought has been attributed to La Niña, a period of oceanic cooling in the Pacific Ocean which began in 1998. The oceanic cooling effect of La Niña reduced the amount of tropical rain precipitation, leading to drought conditions in states like Colorado. Less water to Colorado forests dried out the older, more susceptible lodgepole pines decreasing their overall health and making them a prime food source for the MPB. This had the effect of exponentially increasing the rate of infestation by MPB. For example, in 2002, only four million acres of forests were inflicted with pine beetle. That figure jumped to over ten million acres (representing a 250% increase) in just 12 months.
The second major factor contributing to the MPB epidemic appears to be related to a cascade of human decisions spanning over nearly two centuries. Human activities and intervention, collectively contributed to something called “increased canopy density” of Colorado’s pine forests. In turn, increased canopy density adversely affected the health of the lodgepole pines and made them greatly susceptible to MPB. These human activities and interventions include forest fire suppression, proliferation of the livestock grazing and logging industries, and, rather ironically, the banning of logging activities in certain areas of government-owned forests.
A 1985 study from Oregon State University, demonstrated that the factor most effecting lodgepole pine forest health was the density of the pine forest canopy. The study found that dense forests cannot obtain ideal amounts of photosynthesis needed to maintain health and produce enough carbohydrates to meet growth needs and defensive needs through production of allelochemics. Proper levels of photosynthesis keep lodgepole pines relatively immune from MPB and the fungi spores they carry. Their experiments showed that a thinner canopy was even more valuable than nitrogen fertilization.
Historically, naturally-occurring fires (usually caused by lightning) helped keep the forests in an overall healthy state by thinning the forests canopy, which meant that the understory (the low-laying layer of vegetation beneath a forest’s tree tops) and the canopy had sufficient exposure to collect light for photosynthesis. Non-indigenous people such as European settlers, however, focused efforts on fire suppression. Rather than being nomadic as many native people were, Euro-settlers inhabited the land on a relatively permanent basis. Fire was now considered a danger because it could destroy man-made structures and threaten crops and livestock; whereas native peoples simply migrated away from fires.
As a result of the behavior of European settlers, the composite of Colorado forests today differs significantly than the pre-European settlement forests. Pre-European-settlers in the American western forests (prior to the 1600s) hosted only 40 to 50 trees per acre. By 2002, many forest slopes in the ponderosa-lodgepole pine strata hosted 200 to 400 trees per acre – a 500%-1,000% increase in forest density.
Livestock and livestock grazing of Euro-settlers also significantly contributed to the increased density of American western forest land. Livestock grazing minimizes grasses and leaves on shrubs which normally provide a fuel source for forest fires triggered by lightning strikes, thus again reducing the incidence of naturally-occurring forest fires; the net effect being increased density to forests and decreased photosynthesis among the pine. Livestock grazing did plateau during the late 1800s and early 1900s due to a massive drought in the area, making it difficult for ranchers to maintain large populations of herd. However, this livestock grazing setback failed to relieve the forests’ increasing canopy density because a new threat quickly emerged: logging.
Logging was reaching new heights of productivity at this time and newly cleared lands gave young trees an opportunity to take root and grow. At first glance, this may seem like a good thing, however, an ecosystem is incredibly complex and human intervention often has unforeseen consequences. In Colorado’s case, and indeed in the American western forest lands in general, poorly managed, large-scale logging efforts over the course of a century collectively produced a new, single generation of young trees. The net effect was large forest acreage, all of the same relative age. A forest stand lacking diversity in age is more susceptible to insect infestation than an integrated, multi-generational forest. This is, yet another, major contributor to Colorado’s pine beetle epidemic.
To be continued...
- -- Do you have ideas about how to address this issue? If so, please leave a comment below or contact us at GRIPS - GReen Idea Protection Strategies
References
Kaufmann M.R. et al. Good Fire, Bad Fire: How to Think About Forest Land Management and Ecological Processes. Report (Rocky Mountain Research Station, n.d.).
Sowers, R. & Daoust, D. Western Bark Beetle Assessment: A Framework for Cooperative Forest Stewardship. Report (Western Forestry Leadership Coalition, Lakewood, Colorado, 2009 updated).
Waring, R.H. & Pitman, G.B. 1985. Modifying lodgepole pine stands to change susceptibility to mountain pine beetle attack. Ecology 66(3), 889-897.
Ibid.
Kaufmann M.R. et al. Good Fire, Bad Fire: How to Think About Forest Land Management and Ecological Processes. Report (Rocky Mountain Research Station, n.d.).
Ibid.
As a Rocky Mountain regional example, by 1907, an 881,841 acre region (1,378 square miles) in southern New Mexico was home to 17,000 cows and horses, 10,000 sheep, and 40,000 goats. Colorado, no doubt experienced similar industry trends.
Kaufmann M.R. et al. Good Fire, Bad Fire: How to Think About Forest Land Management and Ecological Processes. Report (Rocky Mountain Research Station, n.d.).
Kaufmann M.R. et al. Good Fire, Bad Fire: How to Think About Forest Land Management and Ecological Processes. Report (Rocky Mountain Research Station, n.d.).
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