British Columbia

Beware of falling trees: Drought affects root stability, say Vancouver Island forest experts

Local tree experts say unusual island drought and blustery weather should remind us to be aware of our surroundings while outdoors. Long periods of dry soil will kill the fine mesh of roots that prevent the trees from falling.

Long periods of dry soil will kill the fine mesh of roots that keep trees from falling

Big trees like old-growth cedars on Vancouver Island are particularly susceptible to drought. ((Chris Corday/CBC))

You may be questioning your safety in the wilderness after a teenager was killed Wednesday by a toppling tree near Sooke, B.C., while on a hike with his classmates.

Local tree experts say unusual island drought and blustery weather should remind us to be aware of our surroundings while outdoors, as long periods of dry soil will kill the fine mesh of roots that keep the trees from falling.

'Unusually dry'

"The last couple summers have been unusually dry," said Barbara Hawkins, a tree physiologist at the University of Victoria, echoing widespread concern over increasingly parched conditions on Vancouver Island. 

Earlier this month, the B.C. government moved the drought rating for Vancouver Island and the Gulf Islands to Level 3, which calls for voluntary water conservation measures.

Hawkins said drought would first attack the stability of trees that are already stressed, like grand firs that may be dealing with root rot.

"Then you have a dry spell on top of that and [it] puts them over the edge," she explained.

Keep an eye out for dying branches that may have discoloured leaves or needles — like this western red cedar — and steer clear of leaning trees. (Nick Page)

Cedars in danger

Many western red cedars, an abundant species on Vancouver Island, have been particularly susceptible as they've reached their tolerance limit to the lack of moisture and are dying, she said.

Many of these cedars cannot withstand eight to 12 weeks of drought.

"You have the big central woody roots which are many years old," said Hawkins. "And they get finer and finer out to the edge of the root system ... That's where the active nutrient and water uptake is happening."

As the soil dries, those finer roots begin to die, and trees "lose that tight connection" in the soil, she said. This is when they're most likely to fall.

Logging or clearing for development can also impact tree stability, said Brian Starzomski, a forest ecologist at the University of Victoria. 

Big trees in Sooke

Starzomski said he visits Sooke on the south end of Vancouver Island every fall, where "big old trees" abound. While beautiful, they can be dangerous, he added. "This is one of those things that ... you can't necessarily predict."

Hawkins noted that falling trees are a natural process within forests, and while drought may exacerbate conditions, so too might an increase in the island's population in recent years. "More people are out recreating in the forest," she explained.

Starzomski said the best thing to do to be safe is to avoid hiking during windy days in areas with large trees, as semi-broken branches might pose serious hazards. Keep an eye out for dying branches that may have orange needles or yellow leaves, and be sure to steer clear of trees that are leaning or have already partly fallen.

If they fall, "it's a lot of weight for some of our really big trees."

About the Author

Adam van der Zwan is a journalist based in Victoria, British Columbia. You can send him a news tip at adam.van.der.zwan@cbc.ca.

With files from Megan Thomas and Yvette Brend

Comments

To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.