Drought conditions increasing risk of hazardous 'zombie' trees in B.C.
They live among us and they could strike at any time.
This is the alarm bell being sounded by arborists about so-called zombie trees. They appear undamaged immediately after severe weather conditions, such as storms and drought, but are in fact damaged internally and can fall at any time.
Severe drought conditions across British Columbia could mean an increased number of hazardous zombie trees this year. Recognizing, and removing them is the only way to protect infrastructure and individuals in harm's way, experts say.
"What ends up happening is the trees are forced to use their stored energy to combat the drought, and they're unable to produce excessive stored energy to fight back against pests, against storms," said Scott Gardner, district manager at Davey Tree Expert Company.
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"We'll see one of two things happen … either catastrophic failure when it does start to rain, or we'll see an abrupt death," he said.
Gardner deals with zombie trees almost daily in Metro Vancouver, but identifying them can be challenging for a non-expert.
He said he looks for signs of rot or mushrooms growing at a tree's root section and abnormal growth patterns, damage or decay in the upper canopy. But some zombie trees can still have a full canopy of foliage, making it hard for people to notice an issue immediately.
"Just today, we had two trees that fell on people's houses and both of them had a full canopy of foliage," Gardner said. "There was root, rot or decay in the root and the tree failed at the base. These are perfect examples of trees that are zombie trees and to the untrained eye would look completely fine."
On the night of Oct. 24, a big zombie tree fell into a residential property in North Vancouver.
"I heard a big snap and a crash and then a thunderous boom and found the top of a tree some 25 feet away from my sliding door," said Karen Tregillas, who lives in the Indian River area in North Vancouver.
The tree in question was a Western Hemlock. It had white fungus in its heartwood, which according to Gardner, makes it a zombie tree.
The same night, windstorms whipped across B.C.'s south coast leading to thousands of residents losing power. According to B.C. Hydro, some outages were due to trees falling on transmission lines.
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"It had crashed right through the chain-link fence," Tregillas said. "I had been worried about that tree before. From my bedroom, I would see the tops and go: 'Oh my gosh, that's a dead tree.'"
Tregillas said she avoids walking her dog in the woods when it's windy outside and tries to be extra cautious even when it's not.
"I've been out there when it's been still as night and you hear a huge tree go down," she said.
Arborist Gardner said the general public should also be on the lookout for zombie trees. People should pay attention to trees on their property and be mindful of any decay, cracks in the bark or discoloured foliage.
This article was originally published for CBC News.
