|Sitka spruce on the beach showing evidence of bark beetles|
These tiny insects survive by boring through the bark of host trees, and excavating tunnels through the phloem - the layer between the bark and wood of a tree. This layer consists of living cells that transport sap which is rich in sugars made by the needles of the tree. Eventually the flow of food and water between the roots and needles is disrupted, and the tree dies.
Bark beetles have been big news in British Columbia over the past few years, as pine beetle attacks in the interior of the province have completely devastated forests. Over 5.7 million hectares have been affected, involving 108 million cubic meters of timber. Resulting clear cuts exceed 250,000 acres in size, representing a second environmental catastrophe, this time human-caused.
South-central Alaskan Sitka spruce forests have been under attack by spruce beetles since a major infestation started there several decades ago. In the current outbreak, spruce beetle activity in Alaska was mapped on over 1.3 million acres in 1997. Cumulative beetle activity now totals over 3 million acres statewide since 1989.
|Tracks show where bark beetles have eaten |
the phloem layer under bark
BC's coastal forest is also affected by the activities of bark beetles, and although they leave beautiful patterns on the wood they feed off of, their activities are decidedly deadly.
Warming temperatures due to climate change are making it easier for bark beetles to overwinter and mature, which is causing numbers to explode.
Bark Beetles in British ColumbiaThe main species in B.C. are the mountain pine beetle, spruce beetle and the Douglas-fir beetle.
- Spruce beetles attack Englemann spruce, White spruce and Sitka spruce trees from late April to early May. These insects have a two-year life cycle.
- Douglas-fir beetles attack trees from late April through May and have a one-year life cycle.
- Mountain pine beetles attack Lodgepole pine, Ponderosa pine and White pine trees from mid July to mid August. Mountain pine beetles have a one-year life cycle.
|Amazing patterns under the bark of this Sitka spruce|
10 Facts about Bark Beetles and North America’s Infestation
1. Other than human beings, no creature on the planet can change a landscape as fast as the bark beetle.
2. Bark beetles are not pests. They collapse and renew forests on time frames inconvenient for humans. For tens of millions of years they have been pruning or collapsing ailing, aging or drought stricken forests. A bark beetle can probably hear the distressed song of a drought stricken tree.
3. Climate change triggered the epidemics and allowed the mountain pine beetle, in particular, to expand its empire into a larger geography: mountains, northern latitudes and the boreal forest.
4. The beetles also took advantage of human engineered landscapes where decades of fire suppression has created a seemingly stable base of scenery that is really volatile.
5. Bark beetles prey on large trees in packs and behave much like wolves and killer whales attack when hunting. These highly social creatures also communicate by sound and chemical perfumes.
6. The great bark beetle epidemics of the last decade killed more than 30 billion conifers from Alaska to New Mexico.
7. Beetle epidemics are like hurricanes. Spending billions of dollars to control them is like putting up fans along the coast of Louisiana to stop another Katrina.
8. Novel sound experiments with bark beetles in Arizona have turned the creature in cannibals and may revolutionize insect control.
9. Canada used to have one of the world’s best insect monitoring programs on the planet. The federal government killed the program in 1996 to save money just as the pine beetle emerged in British Columbia and did $50-billion worth of damage.
10. The bark beetle, says Canada’s greatest living ecologist Buzz Holling, are really harbingers of things to come: collapse and renewal. He reckons that the extreme, the small and the improbable will decide our future.
- from: Empire of the Beetle