Determined to save native species in Toronto's ravines, University of Toronto PhD forestry student Eric Davies has begun a campaign. It involves lobbying the city, enlisting support from other foresters, and drawing public attention to the problem of invasive species, which are the biggest threat facing Toronto's ravines.

With science, money, political will, support from tens of thousands of local residents and a team of foresters leading the effort, Davies says he firmly believes the ecological integrity of Toronto's ravines could be restored. He calls his plan "Rewilding."

On a recent walk through a ravine near downtown Toronto, Davies pointed out the non-native trees. Dead trees were scattered about the forested area. There was garbage, and invasive species had taken root.

"Norway Maple, Norway Maple, Norway Maple," he says. Then, halfway down a steep slope, he spotted a towering Eastern White Pine. "Here, look at this. This looks to be a survivor."

Species such as the White Pine, Ontario's provincial tree, are in decline in Toronto's ravines. This survivor, near Sherbourne Street and Bloor Street East stood tall, its canopy extending high above the forest floor. Davies says he thinks the tree is about 100 years old. He calls it a "treasure" and a "really high-value tree." Clearing out the invasive species near its base could help it regenerate naturally, he says.

"The thing about these trees, you don't realize, is our descendants will not see these trees this big," he says. "We're losing these."

A Red Oak tree provides shade in a ravine near downtown Toronto. Eric Davies says: 'The thing about these trees, you don't realize, is our descendants will not see these trees this big.' (Muriel Draaisma/CBC)

Ravines make up nearly 17 per cent of Toronto's land mass, or about 11,000 hectares and Torontonians love them. Sixty per cent of Toronto's ravines are on public land, with a full 40 per cent on private lands. The city's ravine strategy, passed in October 2017, is based on five guiding principles: protect, invest, connect, partner and celebrate. There is as yet no money attached to the strategy.

Public-private partnership could begin to fix problem

A public-private partnership, a co-operative arrangement involving the public and private sectors, is the answer to the problem, Davies says. It could be styled after the Natural Areas Conservancy in New York City, a non-profit group. It could also draw upon the resources of the Toronto and Region Conservation Authority (TRCA).

Natural Areas Conservancy scientists researched, collected data, interviewed park users and analyzed New York City's green spaces. With the help of New York City's parks and recreation department, the group developed a 25-year "Forest Management Framework." That long-term plan includes planting trees. Toronto could follow suit, Davies says. New York City's forests, he notes, are in better shape than those in Toronto.

"The problem is so big that the only thing that can fix it now is to utilize private funding to help buoy up the capacity of the city, the TRCA, and all of these people that want to help out," he says.

Davies says some "excitement" around the ravines is needed as well.

A White Ash tree displays a D-shaped exit hole from an Emerald Ash Borer, a beetle. (Muriel Draaisma/CBC)

Invasive species can either be removed manually, applying herbicides, or using bio-control. Large groups of volunteers can weed out the unwanted plants, he said, while herbicide application carries possible health risks. Bio-control involves using non-native insects to eat invasive plants, but extensive research is required beforehand, Davies says. Goats can also be used to graze invasive species.

If nothing is done, the ravines that weave through Toronto will continue to be overrun with such invasive species as Norway Maple trees, Japanese Knotweed, Dog Strangling Vine and Garlic Mustard. The ravines will become silent, green deserts that do not support native insects, birds and mammals.

Eventually, the invasive species will reach a critical mass where they will stabilize and it will be extremely difficult to dislodge them, he says.

Eric Davies, a University of Toronto PhD forestry student, spoke to alumni at a lecture in May about his plan to save the city's ravines. (Muriel Draaisma/CBC)

"Once you let an invasive species get to a threshold, it can be very, very difficult to get rid of them. We want to try to prevent it from getting to that critical mass," Davies says. "If you get on this stuff now, it's possible to get a handle on it. You still have the power of nature here to go with you. If you just get rid of the weeds, like a garden, they will come back. The difficult thing is once all local species get to a low level. Even getting the genetic material is challenging."

Walk through ravine reveals extent of decline

In the walk through a ravine alongside Rosedale Valley Road, between Sherbourne Street and Bayview Avenue, Davies spotted Sugar Maple, Black Walnut, Red Oak and White Ash trees, all native species in decline. He also pointed out a Basswood tree and a diseased Butternut tree. The latter is one of two endangered tree species in Ontario.

There was an Alternate Leaf Dogwood, a shrub native to Ontario, with many seed pods, in the middle of one slope. All native trees and shrubs, however, were dwarfed by the masses of invasive species, particularly Norway Maples.

One area of the ravine was clearly used as a dumping ground. There was a full white garbage bag, a discarded laundry basket, a blue recycling partway down the slope, lots of dirty clothing, a used needle, and lots of empty pill containers made of amber plastic.

Eric Davies stands in the middle of green wall of Japanese Knotweed, an invasive species, by the side of Rosedale Valley Road. (Muriel Draaisma/CBC)

Councillor, dean support plan to restore ravine ecology

Davies has support for his plan to restore the ravines from Coun. Mike Colle, who represents Ward 8 Eglinton-Lawrence, and Robert Wright, dean of the University of Toronto forestry faculty.

Colle says the plan is the only way that the city will save its ravines for future generations.

"Right now, we're just treading water. We're just getting by. But if we don't create a new, invigorated model to protect and conserve our ravines in a very proactive way, we are going to lose the battle. We'll either be choked by garbage or choked by invasive species," Colle says.

"It's going to take a much bigger, wider public effort to turn the corner here. We are really at a crossroads. The public is sort of lulled into a false sense of security because they see all of this green. But they don't realize most of that green is invasive species that are choking out all of the other native plants and it's going to continue to do that."

Colle says council has been beset by one financial crisis after another because of provincial government cuts and has not had time to focus on other problems. He himself set up a "Save our Ravines" organization to rally people across the city to adopt local ravines. He is still planning to lead walks through ravines.

Wright, for his part, said Toronto has taken its ravines for granted. "We definitely are supportive of any strategy to preserve our ravines," he says. "Restoration of the ravines is an urban forestry objective."

Dog Strangling Vine, an invasive species, can be found all along the edges of Don Valley Parkway. (Muriel Draaisma/CBC)

Not everyone supports the idea of a public-private partnership, however.

Council passed a motion in February calling on the city manager to report back on the feasibility of establishing a ravine conservancy. Council said the conservancy could engage the public, solicit public and private donations and raise the money needed to deal with "ecological threats" facing the city's ravines. A report is expected this fall.

Coun. Shelley Carroll, who represents Ward 17 Don Valley North, voted against the motion. She wants the city to fund its ravine strategy and take ownership.

"We made a plan. We should fund it," Carroll says. "I firmly believe the reason we have held onto our ravines is through keeping the ownership and management public. I really don't want to let the public sector off the hook."

As for Toronto Mayor John Tory, his spokesperson Don Peat says the mayor is committed to protecting and improving the ravines. He says city staff are working on a ravine strategy implementation plan that envisions different partnership models. These include partnerships with foundations, "friends of" groups and communities that want to care for ravines in their neighbourhoods.

An Alternate Leaf Dogwood, a native shrub, looks healthy in the midst of invasive species. (Eric Davies)

"Partnerships in our ravines will work to increase engagement and contribute to our ravines in sustainable fashions," Tory says. "Staff are currently reviewing the merits of public-private conservancies in our ravines and any benefits compared to other partnership models. The mayor looks forward to the results."

The city, meanwhile, already works in partnership with the TRCA, property owners and utility providers to protect and maintain the ravines, according to Jane Arbour, spokesperson for the city's parks, forestry and recreation division. The city spends about $10 million on ecological management. Much of that goes toward forest management in natural areas, mostly the ravines.

Forest management includes tree planting, control of invasive plant species and introduced pests, volunteer stewardship, monitoring, general maintenance, ravine bylaw permit review and enforcement.

"Staff monitor the growth of invasive species in the city's ravines and forested areas and limit the spread of invasive species through traditional methods and a robust program of engaged volunteers," she says.

Arbour says the ravine strategy is supported by what the city calls a "stewardship model." That means "volunteers participate in planting, maintenance and monitoring activities through events hosted by the city in partnership with local community groups, and through the city's stewardship program," she said.

But Davies says if Toronto's "deep, narrow, forested valleys" are to remain healthy, the city needs to do more and soon.