[audio:http://wamcradio.org/EarthWise/wp-content/uploads/2012/04/EW-06-01-12-Pine-Beetles.mp3|titles=EW 06-01-12 Pine Beetles]
Mountain pine beetles are decimating pines in Canada and the Western United States. And unlike many of the forest pests that ecologists lament, the insects are native to North America.
Historically, mountain pine beetles helped forests regenerate by attacking old, weak trees and making way for new growth. The recent epidemic has been sparked by a combination of warm, dry weather and forests filled with mature pines.
The beetles kill trees by boring into their bark and laying eggs. They introduce a fungus that blocks water and nutrient transport. The combined stress of feeding larvae and fungal attack can kill infested trees within a year. Signs that a tree has succumbed include reddish needles and popcorn-like masses of resin on the tree’s bark.
In the western U.S. it has been getting warmer earlier, and recent summers have been hot and dry. A new University of Colorado study found that beetles are now reproducing twice a year instead of once—and their range is moving northward.
Millions of pine trees are dying at a time when the U.S. is counting on forests to help store carbon dioxide that would otherwise drive climate change.
Sadly, attacked forests become a source, not a sink for carbon dioxide. A study in a single area of British Columbia found that impacted forests released carbon dioxide equivalent to 75% of the annual emissions of carbon dioxide from forest fires across all of Canada.
Climate change is likely driving the severity of beetle outbreaks, and these outbreaks are poised to further exacerbate the threat of global warming.
Web Link
http://www.nytimes.com/2012/04/17/science/beetles-birth-explosion-puts-pine-trees-under-stress.html
Photo, taken on November 15, 2011, courtesy U.S. Department of Agriculture via Flickr.