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Climate change a boon to destructive beetles in Alaska

11/Sep/2006: The population of the Spruce Bark beetles in the forests of Alaska has been exploding with the climate change, as warmer climates provide a favorable environment for the beetles to reproduce at a much faster rate.

More and more beetles are surviving the Alaskan winter more successfully, as the winters are lot warmer now. Warmer summers are assisting these beetles to mature fast and start reproduction within a year’s time instead of two.

Warmer winters are also harming the spruce trees by making them more prone to the bark beetle attack, as the wet and heavy snow formed during warm winters break the top of the spruce trees making it easy for the beetles to bore in to their trunks and feed on the cambium layer, killing the trees in the due course. Spruce trees resist beetle attacks with pitch made up to 17 forms of terpene, a class of hydrocarbons produced commonly by coniferous trees like spruce.

The ratio of terpene in the tree’s outer surface signals the health of the tree. When the spruce tree tops are broken by heavy snow, this ratio gets disturbed and the spruce bark beetles senses this vulnerability by using complex chemical receptors and starts attacking the injured tree. When an entire forest of spruce trees is injured or stressed their terpene ratios goes haywire and the beetles overcome the tree’s defenses easily and kill the trees. Aerial surveys shows that spruce bark beetles have destroyed spruce trees spread over 4.4 million acres in the last three decades.

With Alaska experiencing hot summers over the last two years the number of spruce bark beetles have exploded and with spruce trees stressed by two consecutive warm winters another invasion of spruce bark beetles on the forests in this region, seems inevitable.

Kesavan Siva

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