How a beetle outbreak may have caused two sawmill explosions in B.C.

WATCH ABOVE: A preview for 16×9’s investigation, “Deadly Mills”

It’s a bug the size of a grain of rice, but it has an appetite as big as British Columbia.

With a little help from climate change, the mountain pine beetle has killed or infected 8.7 million hectares of the province’s lodgepole pine forest since 2005. That’s an area almost three times the size of Vancouver Island.

If you’re looking for the cause of the sawmill explosions that killed four workers and injured dozens more in 2012, the beetle is a good place to start.

READ MORE: 16×9 investigation: What was behind the deadly B.C. sawmills explosions?

The insects nest in trees 80 years or older. The female beetles lay their eggs under the bark. A year later, the tree becomes sick as the bug activity cuts off the flow of water and nutrients inside the tree. A year after that, the needles fall off, and the tree turns grey. It’s now effectively dead.

Cold arctic-like temperatures kill the beetle, but after a succession of warmer-than-normal winters in B.C. after 2005, due mostly to climate change, the insect flourished.

The lodgepole pine is the most common tree harvested in the B.C. Interior.

But even after it becomes “bugwood” it has commercial value. Affected areas in the province have seen intense logging activity, even after the bug crisis hit.

The shelf life of a “dead” pine is about five years, meaning that logging companies had to move quickly.

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A lot of sawmills, like Babine and Lakeland, became very busy. And very dusty. And very profitable.

As WorksSafeBC said in its Babine explosion investigation: “The more lumber processed, the greater the profit.”

As the mill ramped up production, “a similar effort was not put into controlling the potentially explosive levels of dust created… It was a formula for trouble that would return to haunt the owners, and their employees.”

READ MORE: How sawmill dust explosions happen

The trees also generate a resin in their fight against the beetle. This resin makes the wood even drier.

Sawmills built 30 or 40 years ago aren’t designed for the fine dry dust that settles everywhere. The dust can overwhelm the mills’ ventilation systems.

After a fire and small explosion in February 2011 in the Babine mill, even the mill’s American owners, Hampton Affiliates, could see something was wrong. WorkSafeBC quotes a Hampton report that found that Babine “has a tremendous amount of dry wood dust fire, resulting in a very large fuel load.”

A year later, that “very large fuel load” was likely to blame when the plant was destroyed in a catastrophic explosion. And the bug’s destructive work was done.

16×9’s “Deadly Mills” airs this Saturday at 7pm.