The mountain pine beetle epidemic in North America has killed 42 million acres of trees, which is an immense number of dead trees! I had heard rumours of this outbreak but it wasn’t until I read about some research at the University of Washington to recycle the dead trees that I stopped to consider what happens in the beetle’s aftermath.
I wrote about the research in a short news story for Dusk Magazine (if you a joining me here from Dusk- Welcome) and this seemed like a good place to further explore the mountain pine beetle epidemic.
A plague on all these trees-ees
Native to North America, the black mountain pine beetle, also known as the bark beetle, is smaller than a grain of rice and has a real skill at getting underneath a tree’s skin. Quite literally it burrows underneath the bark (creating structures known as pitch tubes) and lays its larvae, while also infecting the tree with a fungus it carries. This fungus stops the tree from acquiring food and water, which also prevents the tree from flushing out the beetles. The two pronged attack of the feeding larvae and growing fungus kills the tree.
The current epidemic has been going on since 1997. The beetles are more successful in burrowing into older, less resilient pine trees, so it’s mainly the old forest that is affected with newer healthier, saplings better able to deflect a beetle infestation.
Yelling timber
Estimates from the U.S. Forest Service say that up to 100,000 trees killed by beetles fall to the ground every day in southern Wyoming and northern Colorado. That’s a lot of falling trees! Where close to public trails falling timber poses a real danger to hikers, and near towns and villages the dead trees also put electrical lines and property at risk of damage.
But even if they stay upright the trees are still a concern. By preventing the water supply from the roots the fungus dries out the trees, leaving a dry forest with needles stocked in the canopy that can ignite quickly given the right conditions. The forestry service is concerned by the fire hazard posed by the dead trees.
In addition to these safety concerns, the epidemic has had a large impact on the pine tree population that has corresponding affects on the forest ecosystem. Shade and shelter for animals is removed and other impacts such as water run-off have to be considered.
But what caused the epidemic?
There are a couple of causal factors that are thought to have led to the increased number of beetle infestations. The first fits into the well-established trends seen with climate change. An increase in seasonal temperature shifts the balance of ecological systems, and in this case in favour of the mountain pine beetles. Warmer winters fail to suppress pine beetle populations, which along with prolonged summer droughts have enabled the beetles to increase in number at higher latitudes and elevations.
The other key factor in the epidemic is overly dense forestry. This seemed a little counter-intuitive to my ears as I assumed dense forestry would be an indication of healthy trees, but it actually seems to reduce the resiliency of the trees and cause a population build-up of well-fed beetles that boost epidemics.
Dense forestry leads us very nicely onto the next question…
How are the forestry services dealing with the epidemic?
- Thinning forests to increase resiliency and diversity. Prioritizing areas for thinning that are at the interface with human property and activity.
- Planting new forests to hasten land recovery.
- Removing dead beetle-riddled trees to eliminate the hazard of falling trees, again prioritizing critical areas such as campgrounds.
Dealing with the fallout of the epidemic is expensive and while removing the falling/fire hazard the forestry services also want to promote utilization of the dead trees. The grey-blue staining left behind by the fungus makes wood from the trees less desirable for lumber, the obvious use for the trees. However, the distinctive blue stain is admired by some wood workers.
But with 9-million acres of trees prioritized for felling, there are a lot of trees to be used.
Which brings us to the fast pyrolysis method the researchers at the University of Washington are developing. Fast pyrolysis is the burning of wood, super-fast, to produce a vapour that on cooling forms a type of liquid fuel- a useful product to extract from the dead trees. Head over to my Dusk article to read more about this technique to make a cost effective carbon neutral energy resource from the beetle-infested trees.
Science FYI 