Beetles Attack Crater Lake Trees, South Oregon
Climate Change and the Destruction of Whitebark Pines
Oct 2, 2008
Mountain pine beetle (Dendroctonus ponderosae) infestations are nothing new to western U.S. forests, including those near Crater Lake in southern Oregon. And there’s nothing new about an infestation wiping out thousands of acres of lodgepole pines (Pinus contorta). In fact, such infestations are often a natural part of the ecology of lodgepole forests.
But something strange is now occurring. In higher elevations such as those surrounding Crater Lake, the beetles are targeting a new host - the whitebark pine (Pinus albicaulis) - and global warming might very well be behind this sudden migration.
Crater Lake Whitebark Pines
According to the article “Beetle Outbreak Threatens Park Trees,” in the Summer/Fall 2008 issue of Reflections, the official newspaper of Crater Lake National Park, the whitebark pine is a "keystone" species, their seeds providing important nutrition to birds, squirrels, and bears. Indeed, many plant and animal species rely heavily on the whitebark pine, which provides a critical anchor to the high-elevation forests surrounding Crater Lake.
The Whitebark Pine Ecosystem Foundation reports that the whitebark pine can be found in most high-elevation national forests and parks in the western U.S. The pine is a foundation species that promotes biodiversity and has a pervasive influence over the forest community. If the pine is removed from the forest, the effects cascade down that community.
Until recently, the primary threats to the whitebark pine have been fire suppression and blister rust, a non-native fungal disease. But now a new risk has been added to the mix - an upsurge in mountain pine beetle attacks.
Mountain Pine Beetle Infestations
The mountain pine beetle, according to the Reflections article, spends most of its life burrowed beneath the bark of pine trees, where the beetle larvae feed on the phloem tissue (the inner bark). This feeding cuts off the flow of water and nutrients to the tree, effectively starving the tree. When this occurs, the tree’s needles turn a reddish, rust color, and the tree finally dies.
The mountain pine beetle has thrived for millennia in lodgepole pine forests such as those surrounding Crater Lake. Periodically, under favorable environmental conditions, beetle populations explode, destroying thousands of acres of lodgepole pine. One such epidemic occurred near Crater Lake between 1923 and 1930. Currently, the Crater Lake area is in the midst of a moderate epidemic, which began in 2003.
Climate Change and the Whitebark Pine
The Reflections article reports that the whitebark pine is well-adapted to high-elevation cold climates, but the mountain pine beetle is not. However, because of global warming, the normal safeguards provided by colder temperatures have gradually eroded, making the whitebark pine more hospitable to the insects. Indeed, the beetles are now infesting whitebark pines from Yellowstone to Crater Lake, and the one trait that these diverse regions have in common is the warmer temperatures.
In a February 7, 2008 report released by the Crater Lake Institute, Michael Murray, a terrestrial ecologist for Crater Lake National Park, states that one of the park’s most popular whitebark pines - a tree estimated to be 400-500 years old - had recently succumbed to disease and infestation. A postmortem exam revealed two blister rust cankers and evidence of a late-2005 mountain pine beetle attack - a scenario becoming increasingly more common in the park.
The future of the Crater Lake whitebark pine is uncertain. Also uncertain is the full impact on the supporting ecosystem. What is certain, however, is that warmer temperatures have helped to fuel the insect’s reach into high-elevation forests. And the whitebark pine might not survive such an onslaught.
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