The New York Times has an outstanding video, “America’s Disappearing Forests” documenting the devastating impact of the mountain pine beetle (Dendroctonus ponderosae) on lodgepole pine (Pinus contorta) in the Rocky Mountain states. The insect has destroyed about 2 million acres of lodgepole pine forests. Since lodgepole pine typically occurs in pure stands (coming in after fire), the insects are in effect wiping out entire forests.
It is becoming clearer that the main cause of the outbreak is the prolonged drought of more than 8 years, and mild winters. The prolonged drought weakens the ability of the trees to fight off beetle attacks. The mild winters allow higher survival rates in the beetles. Since the western states will only become warmer and growing seasons longer, there is no end in sight to the outbreak except the death of lodgepole pines. This does not mean the end of forests in the region, since other species can occupy the space. However, the loss of a dominant species in an arid environment means that it will take a long time, centuries at least, for the forests to recover.
Picture: lodgepole pine mortality due to mountain pine beetle. Photo courtesy of Jerald E. Dewey, USDA Forest Service, bugwood.org.
America’s Disappearing Forests – The New York Times – Video Library
