Pine Beetle Feedback

Pine beetle infestations in vulnerable boreal forests not only benefit from warming trends. They also exacerbate them, according to new research published in Nature Geoscience, via Canadian Press.

The effects of climate change cascade,” said Holly Maness, whose paper was published Sunday in the journal Nature Geoscience.

“Previous studies have shown that climate change allowed the beetle to flourish. But our work shows that beetle infestations in turn feed back into climate.”

Scientists have concluded that the gradually warming climate has allowed the tree-killing beetle to spread into forests it used to be frozen out of. The report quotes figures suggesting that over the last decade, the bugs have spread over about 20 per cent of the total area of British Columbia, making it one of the largest ecological disturbances ever recorded.

Maness, an earth scientist working at the University of Toronto, decided to study how turning about 170,000 square kilometres of green forest into grey, leafless stands of dead trees would affect the regional climate.

Using temperature data from satellites, she and her team concluded that beetle-ravaged forests were, on average, one degree warmer during the summer than healthy forests.

The reason? Tree sweat, or rather, the lack thereof.

“Trees sweat to help cool themselves in the same way that humans do,” said Maness.

“When you kill a tree, it’s going to stop sweating. That means that solar radiation that was previously spent evaporating water from these trees is now going into heating the surface.”

The original paper is “Summertime climate response to mountain pine beetle disturbance in British Columbia“, Nature Geoscience (2012) doi:10.1038/ngeo1642




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