The hemlock looper moth caused havoc in Stanley Park, volunteers with the Stanley Park Ecology Society are helping in its recovery
The Vancouver park board’s removal of thousands of Stanley Park’s hemlock trees, killed by an infestation of hemlock looper moths, has set off a race for the Stanley Park Ecology Society on a second front of their restoration project.
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While park board crews are replanting tree seedlings in the new open patches, the society’s staff has enlisted a corps of volunteers to step in and plant native flora shrubs alongside them, trying to recreate a healthy forest understory before invasive species can take hold.
“When we have these large canopy gaps, we kind of go back to Square 1,” Dacyn Holinda, conservation projects manager for the Stanley Park Ecology Society, said, while standing in one of those openings on the park’s South Creek Trail, at the edge of the park causeway.
“The important thing is to plant a nice diversity of that understory layer, which will prevent those invasive species from coming to take over,” he added.
In this 2,000-square-metre opening, a platoon of volunteers, with the help of the non-profit Tree Canada, laid down a carpet of almost 500 native plants: salmonberry and salal, huckleberry and Oregon grape, red columbine and ferns of several varieties, including bracken and lady deer.
“We also do our best to work with local (Indigenous) knowledge holders and knowledge keepers to ensure that we’re planting culturally significant plant species,” Holinda said. “So some of the things we’ve been able to reintroduce to the park are things like wild ginger, which we haven’t seen many patches of.
“I think it was just over 30 species that we’ve planted this year.”
Here, that is important because it is also close to a patch of invasive Himalayan blackberry, an aggressive invasive with thick-stemmed vines that Holinda said would thrive in the open sunlight.
“Himalayan blackberry, English Ivy, (are) two really common invasives we have that if they come into the area kind of just dwarf over everything,” Holinda said. “And they create these monocultures where nothing else can grow.”
Paring back those invasive species is another part of the battle. The Stanley Park Ecology Society has a legion of volunteers who dedicate time to hacking them out, particularly Himalayan blackberries, though Holinda reckons, “We’re never going to eradicate it from the park.”
For the Vancouver park board, the ecology society’s work has been “hugely important” as a complement to what has become a controversial plan to remove some 20,000 to 30,000 dead hemlock trees in broad swaths of the park.
Amit Gandha, the director of parks at the Vancouver parks board, said that staff will work with the society to keep track of the health of replanted areas to make sure they aren’t overtaken by invasive plants.
He said the park board is still working on an invasive species management plan for all city parks. Stanley Park has the advantage of the ecology society and its volunteers to keep things in check.
“If we don’t monitor the success of this (replanting) and support it, then I think it’s a disservice to this whole project,” Gandha said.
The hemlock looper moth is an endemic insect to coastal forests, The larvae feast on the needles of hemlocks, killing them off.
Their populations rise and fall in cycles and the latest massive looper moth infestation covered Stanley Park and the North Shore with nightly clouds of insects during the late summer of 2020. Through 2022, the abundance of moths killed some 160,000 trees in Stanley Park.
The park board’s plan is to cull some 20,000 to 30,000 of those trees, trying to limit removals to the biggest trees that pose a danger if they were to fall in the most heavily used areas of the park.
Some 8,000 trees were removed in large areas along the Causeway and around Prospect Point in the first of three phases of the project last winter.
Around 4,000 dead trees near Brockton Point and on the steep slopes west of Prospect Point were to be removed in the second phase this winter, but park board staff found that heavy rain and wind storms during the fall have caused havoc in the dead patches, prompting them to speed up the pace of removals, which has proved controversial with some park users.
The park board approved the acceleration of removals at its Dec. 9 meeting, over the objections of a new group calling itself the Stanley Park Preservation Society, which has argued the removals are doing more damage to the park.
In October, society representative Michael Caditz argued that only individual trees that are assessed to be dangerous should be removed and large-scale removals are only increasing the risk for invasive species to establish.
On Dec. 13, the Stanley Park Preservation Society sent out a news release arguing that the reports park staff submitted to back up the acceleration plan weren’t conclusive enough to justify the speed-up.
Allan Carroll, a University of B.C. forest ecologist, said the risk of trees falling in places frequented by people forces the parks board to remove dead trees. Restoration, he said, is about making sure all of the elements of what would be a healthy forest are allowed to grow.
“It’s hard to decide when, where and how to do these sorts of things and the extent to which you have your interventions,” said Carroll, director of forest science in the faculty of forestry.
Carroll said replanting is often necessary as part of restoration. However, Stanley Park is a highly productive ecosystem, so sometimes just paring back the invasive plants is enough for native plants to return.
Next to the South Creek trail, Holinda is pleased to see vines of trailing blackberry, a gentler variety, creeping in around the edges of the cleared area.
“Stanley Park is difficult because some people like to think of it as this untapped wilderness, but really it is a very actively managed park.”
“On the other hand, we’re quite lucky in that it’s still healthy enough, relative to a lot of other urban parks, that it can regenerate itself.”