Tiny Beetle, Big Impact (broadcast Friday, April 25th, 2008)

Trees killed by mountain pine beetle turn red in the year following mortality, revealing the extent of damage in affected forests. This valley is located in south western British Columbia, Canada. Natural Resources Canada

Forests are usually seen as a positive force when it comes to greenhouse gas calculations. On average, an acre of forest can absorb around 2.5 tons of carbon dioxide per year. But what happens if all those trees suddenly were to die?

In parts of Canada, forests are being hard-hit by an outbreak of the mountain pine beetle (Dendroctonus ponderosae). Though the beetles are small -- under a third of an inch long -- they are very hungry, boring through the wood of a variety of pine tree species, especially ponderosa, lodgepole, Scotch and limber pine. The severe outbreak of the beetles in Canada is killing enough trees that ecologists are worried that forests in British Columbia could change from being a 'carbon sink,' absorbing carbon dioxide emissions and sequestering them, to a 'carbon source,' releasing stored up carbon dioxide as the trees die and decompose or burn in forest fires. Warming temperatures are allowing the beetles to spread into new territory, threatening more forests.

"The current outbreak in British Columbia, Canada, is an order of magnitude larger in area and severity than all previous recorded outbreaks," researchers wrote this week in the journal Nature. One outbreak of the beetle alone released enough carbon dioxide to equal five years worth of emissions from transportation sources in Canada, the researchers found. We'll talk with one of the researchers involved with the study about the work, and how a tiny beetle could have a significant impact on the carbon balance in North America. Teachers, find more information about using Science Friday as a classroom resource in the Kids' Connection.