Mountain pine beetle

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The mountain pine beetle, Dendroctonus ponderosae, is a species of bark beetle native to the forests of western North America from Mexico to central British Columbia.

Mountain pine beetles killed these pine trees in Prince George, British Columbia.

Mountain pine beetles inhabit pines, particularly the Ponderosa Pine, Lodgepole Pine, Scots Pine and Limber Pine. The bristlecone pines and pinyon pines are less commonly attacked. During early stages of an outbreak, attacks are limited largely to trees under stress from injury, poor site conditions, fire damage, overcrowding, root disease or old age. However, as beetle populations increase, the beetles attack most large trees in the outbreak area.

The beetles kill the trees by boring through the bark into the interior of the tree and eating away at the soft woody tissue inside. The trees respond by increasing their resin output in order to discourage the beetles, but the beetles send out pheromones for reinforcments. Over time, the trees are overwhelmed as their interiors are eaten away, cutting off the supply of water and nutrients. In the end, the trees starve to death, and the damage can be easily seen even from the air in the form of reddened needles. Entire groves of trees after an outbreak will appear reddish for this reason.

The beetle is responsible for massive damage to lodgepole pine forests in Canada, where a reduction in the severity of winters has allowed their population to explode. Canadian forestry officials have allowed increased logging to remove beetle-damaged trees, but remain worried that without a return of cold snaps to reduce beetle populations, the beetles will make their way across the Canadian Rockies and decimate the forests in the tourist region of Banff, Alberta, and the boreal forest regions, which accounts for nearly one third of the world's total forest area. Logging in the beetle-infested areas reduces the risk of forest fires by removing dead wood, and also allow surviving stands to recover and regrow faster.

Mountain pine beetle infestations have already been reported as far north as northern British Columbia, Jasper National Park and northwestern Alberta. Unlike the forests in British Columbia, Alberta's forests have evolved without widespread beetle outbreaks because the winters on the eastern slopes of the Rockies are generally colder and more prone to periods of very cold weather, where temperatures down to -30°C to -40°C (-22°F to -40°F) for at least several days kills most mountain pine beetles. The recently mild winters have Alberta forestry officials worried because the beetles will have a devastating impact on an ecosystem which may be ill-equipped naturally to deal with it.

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