Drought and moths push the trees of Vancouver’s Stanley Park to the brink

People in Vancouver’s Stanley Park, on Oct. 12.JONATHAN HAYWARD/The Canadian Press

First got here the moths. Then got here the drought.

The trees of Stanley Park, typically the green jewel of Vancouver’s downtown core, just can’t catch a break.

Experts say large numbers of browning trees appear dead or dying, due to a one-two combination of foliage-munching grubs and an exceptionally dry weather spell, with the last appreciable rain falling in Vancouver on Sept. 4.

City of Vancouver arborist Joe McLeod said trees already stressed by infestations of western hemlock looper moth larva have been further pushed toward breaking point by the prolonged summerlike conditions.

“Very like humans, the more stressed we’re, the more susceptible we’re to getting colds and other conditions,” said McLeod.

“Unfortunately, I feel the proven fact that there’s an insect outbreak that is occurring and the proven fact that now we have very extreme heat after which extreme cold – it’s definitely lending itself to a worse situation than previous years.”

Such “multiple layers of stress” added as much as the next likelihood of tree mortality, said McLeod.

Dead trees may very well be seen within the park’s Prospect Point area, in addition to facing Coal Harbour, English Bay and the northern fringe of the park, said McLeod.

Richard Hamelin, the department head of forest conservation sciences on the University of British Columbia, agreed that it’s not only the continuing problem of the looper moths that’s killing trees.

“The warmth and the drought are like additional stress that affects those trees,” said Hamelin.

“If it were only for the insect, possibly the trees would get well,” said Hamelin, who has been monitoring the health of trees throughout the park during the last 4 years.

McLeod, acting manager of urban forestry, fleet and strategic planning on the Vancouver Board of Parks and Recreation, said the moth outbreak is in its fourth 12 months.

The moth’s larval grubs mostly goal western hemlocks, but will jump to Douglas fir and other species when the hemlocks are consumed.

The moth outbreaks are cyclic, and typically last one to a few years.

The impact of the grubs has made trees particularly prone to the drought conditions, Hamelin said, because the shortage of foliage and buds is making it difficult for trees to store water and get well next 12 months.

McLeod said that spraying Stanley Park’s trees with pesticide could have negative consequences on helpful insects.

He said his team put out a request for proposals last week, asking experts to give you suggestions about tips on how to manage the moth outbreak.

“So our hope is that with the input of skilled foresters and other professionals, we will get a report that guides the response, not only when it comes to risk management but in addition when it comes to tips on how to improve the ecological health of the forest inside Stanley Park,” said McLeod.

He added that the report will even concentrate on tips on how to restore the forest within the face of climate change, in addition to moth outbreaks.

Within the meantime, McLeod said his team would address hazards posed by the dead and dying trees.

That included working with the Coastal Fire Centre, a wildfire risk-assessing body in B.C.

But McLeod said recent cooler nights, bringing dew, could have reduced the chance of a hearth within the park.

“We’re actively pursuing solutions to mitigate risks and move the Stanley Park forest in a greater ecological direction. But that being said, there are various challenges that we’ll encounter and it’s a posh ecosystem,” McLeod said.

“We appreciate the community’s patience as we navigate this and we just need to get it right since it’s such a jewel to the community.”

This story was produced with the financial assistance of the Meta and Canadian Press News Fellowship.


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