Beetles pose climate threat
2008-04-24 12:44
Washington - Mountain pine
beetles that are destroying forests along much of the Rocky
Mountain range are doing so much damage that they may affect
climate change, Canadian researchers reported on Wednesday.
The damage is nearly equivalent to the polluting effects of
forest fires, they report in the journal Nature.
"In the worst year, the impacts resulting from the beetle
outbreak in British Columbia were equivalent to 75% of
the average annual direct forest fire emissions from all of
Canada during 1959-1999," Werner Kurz of the Canadian Forest
Service in Victoria, British Columbia and colleagues wrote.
Usually, a forest is a carbon "sink", soaking up carbon
dioxide that would otherwise affect the atmosphere and help
hold in heat.
The beetle, Dendroctonus ponderosae, changed that. Dead
trees release carbon as they rot, and of course fail to use
carbon dioxide as they would if alive.
"This impact converted the forest from a small net carbon
sink to a large net carbon source both during and immediately
after the outbreak," the researchers wrote.
"The predicted emissions are larger than the total average
sink of all of Canada's managed forest over the last decade."
The beetles lay eggs under the bark of mature lodge-pole
pine and jack-pine trees, eventually killing them. Once beetles
infest a tree, it cannot be saved.
They have ravaged 130 000 square
kilometres of forest in western Canada alone. Hundreds of
thousands of square miles (km) have also been damaged in the
United States.
"Insect outbreaks such as this represent an important
mechanism by which climate change may undermine the ability of
northern forests to take up and store atmospheric carbon, and
such impacts should be accounted for in large-scale modelling
analyses," the researchers wrote.
Ironically, climate warming has allowed the Dendroctonus
ponderosae pine beetle to venture further north.
Woodpeckers and insects such as clerid beetles that feed on
the pine beetles can control them, and early fall freezes can
kill the larvae.
It takes five days of temperatures of at least -30 degrees
F (-34 C) to kill the beetles, according to Colorado State
University researchers.
They used computer models to estimate that the beetles
could undo energy-saving efforts made by Canada to reduce its
carbon emissions as agreed under the United Nations Kyoto
protocol, which took effect in 2005.