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Forests destroyed by mountain pine beetles can be made into valuable engineered wood products.

 

The mountain pine beetle has killed millions of acres of forest across the western U.S., including most of the western slope of Rocky Mountain National Park.
Photo Credit: USDA Forest Service

Balancing our need for timber along with the other environmental and financial benefits of forests has always been a challenge, especially in areas where forests and wildlife are integral to local communities.

On the western slopes of Colorado’s Rocky Mountain National Park, the trees are an integral part of the hiking experience, yet the trees along the trails that I used to run are now all dead and brown or gray as far as the eye can see, killed by the mountain pine beetle.

In this month’s EBN feature, Engineering a Wood Revolution, I look at the use of some of this less “desirable” wood to make engineered wood products and explore whether they can provide a renewable, carbon-neutral building material. In the end, I came away with a better understanding of forestry and carbon sequestration and thought, “This just might be crazy enough to work.”

The Fall and Rise of America’s Forests

Human history is rife with examples of forests being clear-cut without any concern for the social or environmental consequences.

Despite progress in convincing people that forests are valuable assets that should be managed, according to the State of the World’s Forest 2012, published by the Food and Agriculture Organization of the United Nations, more than 321 million acres of the world’s forests have disappeared in the past ten years (the equivalent of about 500,000 square miles, or nearly twice the size of Texas). Much of this forest loss is due to demand for land rather than for wood.

Here in North America, we are a little more fortunate. Though we have cut down massive swaths of forestland over the past two hundred years, we now have 15.5% of the world’s forests, with approximately 745 million acres in the U.S. and 995 million acres in Canada. In fact, forest growth in the U.S. has been outpacing demand.

But that does not necessarily mean our forests are “out of the woods.”

Invaders!

Invasive species like the emerald ash borer and fungi like annosum root rot have devastated trees east of the Mississippi, but no pest has caused as much widespread destruction as the mountain pine beetle.

This natural member of the Western North American forest ecosystem normally infects weakened or aging pine trees and is a necessary part of the forest ecosystem, but drought conditions and abnormally warm winters brought on by a warming climate have made unprecedented swaths of forest vulnerable to attack.

As the beetle burrows into a tree, a fungus that hitches along for the ride inhibits the tree’s ability to defend itself from attack. The fungus also stains the wood blue, lowering the value of the wood. The trees die but remain standing until toppled by storms or gravity, and the wood can be difficult and dangerous to salvage and sell as lumber.

Since the beetle outbreak began in the late 1990s, approximately 33 million acres of trees have been killed in Canada, with another 4 million acres lost in the Rocky Mountain region of the U.S. The extent of the die-off places watersheds at risk from contaminants, and the standing dead trees present a significant fire and safety hazard as well as providing another potentially significant source of atmospheric carbon as the trees burn or degrade.

Seizing the moment

Here we have an opportunity to make the best of a bad situation.

Trees damaged by climate change that will add additional CO2 to the atmosphere if we leave them as is are now being harvested and used in engineered wood products. Instead of creating a carbon feedback loop, this lower-value wood can be used in structural products to sequester carbon.

It’s not ideal, but the net benefits are cumulative when this wood is used structurally in place of more energy-intensive, CO2-producing steel or concrete.

In the feature article, you can see images of cross-laminated timbers (CLT) from Structurlam and the engineered wood ceiling of the Richmond Olympic oval: both use beetle-kill wood.

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