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Invasive species and poor water management are threatening the web of rivers, creeks and valleys that define Toronto’s landscape, and hard work is required to undo the damage. Other cities will face similar challenges as their ecosystems weaken

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Just south of Bloor Street West in Toronto, the Humber River forms a pond-like area where many native species live – but it's also the resting place of tires and garbage bags. The reedy grasses in the foreground, called phragmites, are an invasive species, one of many that threaten the city's river ecosystems.Cristian Ordóñez/The Globe and Mail

You can hop off Toronto’s second-busiest subway line at Old Mill station, walk a few minutes down the adjacent ravine, wade into the Humber River and start casting a fly for salmon.

Rob Cesta fishes one of Toronto’s rivers every few weeks during the season. When the most easily accessed spots are too crowded he moves further along, losing himself in the urban wilderness.

”You’re like, wow, I am literally in nature,” said Mr. Cesta, who runs Drift Outfitters and Fly Shop in the city centre. “I could be anywhere in the world, but I’m in the middle of downtown Toronto.”

Cassandra Jowett, who has been paddling Toronto’s waterways for eight years with her husband, says you’re actually more likely to see wildlife there than in cottage country.

“Animals here are just funnelled into these smaller green spaces,” she said. “So I think you do get the opportunity to, you know, be more up close and personal with some wildlife.”

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A hole in a red maple tree is home to a pair of giant saproxylic beetles, one of the most endangered insect species in forest ecosystems.Cristian Ordóñez/The Globe and Mail

Now advocates and policy-makers are exploring how to protect ravine ecologies while also allowing more people to visit them. The need to experience nature has become especially clear during the COVID-19 pandemic, but balancing conservation and accessibility is a complex challenge. Toronto’s ravines – which cover 17 per cent of the city’s land area, stretching between the homes and workplaces of millions – are in serious ecological trouble. But the more people who use these spaces, many advocates argue, the better protected they will be.

“We need people to get into the ravines – on paths – and get to know them,” says Eric Davies, a forestry ecologist who has studied Toronto’s ravines. Advocates say each additional user is someone who will care about the ravines, push politicians to protect them and perhaps volunteer to maintain them.

This will require serious effort and resources. Throughout the ravines, rivers and creeks suffer from a flow of overheated water off the city’s paved roads after summer rainstorms. Recent research by the University of Toronto studied 214 sites along waterways, finding that salt dumped on streets had raised the salinity of 89 per cent of them past the federal chronic exposure guidelines for chloride.

The delicate ecology of the ravines’ forests and savannahs has been disrupted by invasive species. Volunteers organize campaigns to collect garbage and pull out encroaching garlic mustard plants. The ominously named dog-strangling vine is common.

None of this may be evident to a casual ravine visitor. But if you are an expert, “you see it everywhere,” said Mr. Davies, who is now chief ecological officer at the ecology consulting firm Wilder. “The native ecosystem has declined by 50 to 70 per cent, and rushing into that power vacuum is almost exclusively invasive species.”

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At top, piles of garden waste lie on the edge of Cedarvale Ravine. Such waste can introduce non-native species that throw the ecosystem off-balance. Forestry ecologist Eric Davies, bottom left, focuses on the ravines' native species, like the American witch-hazel whose seed pods he is shown examining at bottom right.Cristian Ordóñez/The Globe and Mail

The invasion begins with the trees, which are the “anchors” of the ecosystem, he said. One problem: Native sugar maples are in decline, while Norway maples, an imported species widely planted as street trees in the 20th century, have spread into the ravines. The intruders issue 10 times as many seeds as the sugar maples, starting at a younger age. But they are also toxic to native insect species and inhibit the growth of native plant species like the trillium.

“The diversity of species has gone way down,” Mr. Davies said. “The richness of the ecosystem has gone way down.”

He argues that what’s needed is large-scale interventions: culling invasive plant species, and replanting native ones. But he doesn’t want people to be kept out of these spaces – he wants them to explore them. That is also an ongoing goal of Toronto’s Ravine Strategy, established in 2017. Kim Statham, acting director of urban forestry at the City of Toronto, explains that the plan aims to restore the city’s ravines using a joint emphasis on ecology and social equity. “We want to protect these places, and also make them more accessible to a wider range of Torontonians,” she said.

For now, use of the ravines still seems to skew heavily white, even in parts of the city with many racialized people. Mussarat Ejaz helps encourage broader use. A community health worker in Flemingdon Park, a neighbourhood of high-rise apartments perched on the edge of the Don Valley, she has led walks and participated in training sessions to encourage those unfamiliar with the nearby ravine to visit it.

This is a significant challenge. Flemingdon Park was built in the 1960s with few routes down into the valley. Today most residents are immigrants to Canada, for whom the quasi-wilderness of the forested ravine poses cultural as well as physical barriers.

“Some of the folks … although they were kind of walking around the neighbourhood, had no clue that there was this ravine,” Ms. Ejaz said. “There are so many numerous health benefits, you know, especially within the COVID times. We have been encouraging folks to take long walks.”

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A family enjoys a walk at Cedarvale Ravine.Cristian Ordóñez/The Globe and Mail

These large urban green spaces provide more than access to nature for city dwellers. They improve air quality, moderate flooding and are crucial for animal and plant life.

Their value to human health and social health is clear. A 2019 paper in the journal Scientific Reports found that “the likelihood of reporting good health or high well-being became significantly greater” among people spending at least two hours weekly in nature. Some doctors even write prescriptions for people to go for a stroll or spend time in a park.

In an ecological sense, they even benefit residents who never venture there. A 2014 report released by Toronto-Dominion Bank pegged the replacement value of the 10 million trees in Toronto’s ravines system at $7-billion. It noted these forests absorb air pollutants, moderate climate and reduce strain on the city’s water infrastructure – for annual benefits worth $7.95 a tree.

But as places where natural systems intersect with large cities, they are sensitive as well as valuable. And they bear the effects of human activity.

In previous generations, colonial governments and business people viewed ravines as sites of industry – and then, after they became heavily polluted, as places to avoid. In the 19th century the Don River exemplified this: It was lined with mills, factories, tanneries and other polluters. There was also housing, including a handful of privately owned homes and often informal settlements – precursors to the encampments of homeless people that are there today.

This is history, but not ancient history. Only in the middle of the 20th century did the ravines evolve toward their current form.

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Two new lakes form in east-end Toronto after the Don River overflowed its banks in 1954 during Hurricane Hazel.The Photographic Survey Corporation Ltd.

The effects of Hurricane Hazel, in 1954, caused serious flooding in Toronto’s ravines and killed 81 people, many of them in houses torn away by a raging Humber River. As a result, the most vulnerable areas were expropriated and laws written to prevent them being built on. Much of the land was brought under the purview of the Toronto and Region Conservation Authority.

A growing recognition of the green value of these spaces led to tree-planting efforts and cleanup campaigns. But there is still, even after a few generations of greater care and attention, a remarkable amount of human impact evident in the ravines. This winter, city crews were unable to keep up with the bags of dog waste piling up in some places. Volunteers also collect a staggering amount of garbage each year: 74 tonnes in 2020, according to Ms. Statham.

“We’ve pulled out enough car parts to construct at least two cars,” said Floyd Ruskin, one of the founding members of the community cleanup group Don’t Mess with the Don. “Everything else that our industrialized society can construct, somebody’s thrown it into our green space.”

For people like Mr. Ruskin, the ravines’ industrialized past is not a distant memory. He cited plans by the province’s regional transit agency, Metrolinx, to build a facility in the Don Valley as a sign that constant vigilance is needed. “Our belief is that the reintroduction of this is just a spearhead for other types of activities like that, something we turned back the clock on 70 years ago,” he said.

The planned facility is a layover for GO Transit commuter trains, a regional system that is now being significantly expanded. After consultation with the TRCA, transit agency Metrolinx has moved its site incrementally along the valley. The planned facility will now sit alongside the Don Valley Parkway, a major highway completed here in 1961. However, the facility and its access road will also cut into a recently restored natural area in the Don River Valley Park.

That park, a city-owned 200 hectares in the wide lower part of the river valley, is a recent addition to a chain of parks in the valley. The latest addition has been the subject of new cultural planning and ecological restoration over the past five years, and it will benefit from new water infrastructure projects and the remaking of the Don River mouth.

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The Meadoway is a project to turn a Scarborough hydro corridor into a 16-kilometre greenspace linking downtown Toronto with Rouge National Urban Park.Handout photo

It has always been a complex matter for infrastructure, nature and recreational uses to co-exist here, and the balance may be shifting slightly. Toronto’s Ravine Strategy includes a scheme for an 81-kilometre Loop Trail: a path for pedestrians and cyclists that would link the city’s two major river valleys, the Humber and the Don, as a route for recreation and transportation. It would include the Meadoway, a trail system along a hydroelectric corridor that runs east through Scarborough to the Rouge River, the city’s third major river system.

“Through this pandemic, we’ve come to realize that outdoor spaces are vital to the health of cities and people,” said Geoff Cape, chief executive of Evergreen, a not-for-profit organization that operates the Evergreen Brick Works site in the Don Valley and is collaborating with the city and the TRCA on the ravines plan. The Loop Trail “will become a backbone for the ravine system,” he said, allowing people to take a journey around the entire city.

This will mean building 15 kilometres of new trail, linking up the existing but disconnected segments of trails. It will also include “hubs,” Mr. Cape said – including one in Flemingdon Park – that would provide basic amenities such as washrooms, and provide services such as bike rental and repair. For Mr. Davies, it could also provide valuable corridors for native plant and animal species. “If you connect the ravines for people, who else are you connecting them for?” he asks. “For biodiversity.”

The Loop Trail project – and the broader restoration of the ravine system – is complex work. To take one example, red oaks are an important native species here. But Toronto is planting red oaks from commercially available seeds, Mr. Davies said, and the seeds are commonly from Tennessee. They have evolved to bloom earlier in the season, before the insects who feed on them and, in turn, become prey for migrating songbirds. Imported trees, even if they look like natives, can disrupt this delicate sequence.

“A ravine is very complex,” he said. “It’s a natural system, like the human body, and it needs the same kind of attention and care.”

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A concept illustration of Edmonton's Touch the Water project shows the proposed four-kilometre span of walkways it would create around the North Saskatchewan River.DUB ARCHITECTS; STOSS LANDSCAPE URBANISM; & ISL ENGINEERING

Which cities protect ravines the right way?

by Alex Bozikovic and Frances Bula

When you’re in Edmonton, you can’t miss the North Saskatchewan River: The river’s deep, broad valley is a dramatic part of the landscape, and a series of ravine parks stretch through the city. However, if you are downtown and want to get near the water, it’s not easy.

This is a common problem in Canada’s major cities. “The city has really cut itself off from the river,” says Geoff Smith, who oversees open space planning and design for the City of Edmonton. “We are working on changing that.”

A new Edmonton initiative called Touch the Water would create four kilometres of riverside walkways connected to downtown, along with new amenities and gathering places, while also helping to repair the natural systems of the valley and the river.

The project, designed by prominent landscape architects Stoss with local firm Dub Architects, is linked to the River Valley Planning Modernization project, a strategic plan for the valley and associated ravine system.

Edmonton says its network of river valley green spaces is the largest urban park in Canada. And yet, Mr. Smith said, “A lot of heavy industry and extraction took place here – mining, forestry, aggregate extraction.” Now the goal is to improve the state of the forest and river ecosystems. The decommissioned Rossdale Power Plant could find new purpose as an event and cultural venue. “Like river edges in cities and towns across North America,” Mr. Smith added, “this is not a pristine natural environment.”

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The Touch the Water proposal includes a new public plaza next to a former power plant and pump houses.DUB ARCHITECTS; STOSS LANDSCAPE URBANISM; & ISL ENGINEERING

The same is true in Vancouver, which given its topography should have many great ravine parks – but does not. Residents and businesses used ravines as garbage dumps and sewers for decades, before filling in many of them to make more land for houses and an unvarying street grid.

As a result, only about 4 per cent of the land in Vancouver consists of original pieces of the natural environment. In Burnaby, next door, it’s 24 per cent.

The state of Vancouver ravines began changing three decades ago, when people living near some of the last remaining sections started trying to clean them up. “We were filling dumpsters two times a year with everything: universal gyms, home renos,” recalled Carmen Rosen, the director of a group, Still Moon Arts Society, that works on improving the Renfrew Ravine and adding art to it.

Today, the ravine is getting better by the year. Vancouver’s parks department started a rehabilitation plan around 2012. There is relatively little garbage now. Invasive plants that once ran amok have been cleared and replaced with species native to B.C. Salmon have started appearing in Still Creek, into which the ravine creek’s empties.

The Vancouver Park Board is looking at ways to uncover or reconstitute half a dozen former waterways in the city, from Canyon Creek, which currently runs underneath a park near Spanish Banks beach, in the west to a part of Gibson Creek that runs under a field on the east side.

Those kinds of natural places are more and more prized as the city gets denser, said Chad Anderson, a senior planner with the Vancouver Park Board. “All of a sudden these natural spaces are highly valuable.”

That’s even more true for the many Canadian cities that don’t have big intact ravine systems. In Halifax, there’s only one preserved creek in a deep gully, at Hemlock Ravine Park. The park is next to a suburban development in the Bedford area northwest of central Halifax. The ravine is not easily accessible, but it provides a unique refuge that is filled with vegetation not found elsewhere and that muffles the noise of the city.

The Halifax parks department, like those elsewhere, acknowledged that ravines are harder to take care of. They attract fewer visitors, which makes them more susceptible to dumping and other forms of abuse.

In Edmonton, Mr. Smith suggested that bringing people close to the river should help educate them about what the ravine system needs, and build support for that work. “By bringing people to the river’s edge,” he said, “we are promoting ecological stewardship.”

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