The elusive urban forest that lies beneath Toronto

Spectacular ravines offer a wilderness escape in Canada's largest city – and a lesson in the impact of invasive species in an urban space.

By Josie Kao
Published 8 Mar 2022, 09:44 GMT
A pedestrian takes a morning stroll through the Moore Park Ravine in Toronto, Canada. More than ...
A pedestrian takes a morning stroll through the Moore Park Ravine in Toronto, Canada. More than a million people use the ravines in and around the city each year. Revitalization efforts are underway to protect the natural spaces for future generations.
Photograph by Rene Johnston, Toronto Star/Getty Images

An ancient system of ravines underlies Canada’s largest city. Carved by glaciers that receded more than 12,000 years ago, these winding rivers, grassy meadows, underground forest, secret beaches, and micro valleys—constituting one of the largest ravine systems in the world (it’s 30 times the size New York’s Central Park)—shape the geography of Toronto. It’s those ravines that give the Toronto the nickname “a city within a park.

But these ravines, which now cover an estimated 17 percent of the city, are at risk from urban development and invasive species. Decades of rapid urbanisation transformed what was once a thriving ecosystem connecting the major rivers of Toronto. During the early 20th-century, many of the city’s pristine meadows and wetlands were paved over; much of the forest floor became an illegal dumping site; and companies used the streams and rivers as a waste disposal system.

Toronto is home to one of the world’s largest ravine systems, which is 30 times the size of New York’s Central Park.
Photograph by Carlos Osorio, Toronto Star/Getty Images

Fortunately, ongoing efforts to sustain the natural heritage of Toronto are showing signs of success. The revitalization will benefit the environment and locals, as well as adventure-seeking visitors. More than a million people use the urban forest to bike, hike, and discover lesser-known parts of the city each year. In 2021, the city council agreed to invest $66 million (£50 million) toward enhancing the gullies and creating a 50-mile continuous multi-use Loop Trail that will encourage people to explore the city’s ravine system, developing waterfront, and trendy neighbourhoods.

Reviving the ravines

In 2017, Toronto adopted a 10-year strategy to preserve and revitalise the ravines. An important focus of the strategy is the mitigation of invasive species. The ravines are a vital habitat that contains 87 percent of the city’s indigenous wildlife and plants.

These forest ecosystems “are critical to providing climate resiliency,” says Kim Statham, acting director of urban forestry for Toronto, citing how forests reduce what’s known as the urban heat island effect. Cities often report higher temperatures than rural areas because of the amount of roof and road surfaces that absorb and reflect the sun’s rays. Areas with more tree cover are better able to fight these high temperatures, a discovery that is factoring into Toronto’s efforts to protect the ravine system.

However, invasive species such as the Norway maple and Japanese knotweed are harming the native flora. Norway maples, for example, have reproduced so rapidly they have killed nearly half the forest floor with their roots and poisonous sap. As the protective barrier continues to erode, there is a greater risk of floods and native animals losing their nesting grounds.

Anqi Dong, who coauthored a University of Toronto ravine study, found that the amount of non-native tree cover in the ravines had increased from 10 percent in the 1970s to 40 percent in 2016. If the proliferation of invasive species continues at this rate, Dong estimates that it could reach at least 60 percent in the coming decades.

Walkers use one of multiple trails at Toronto’s Rouge Valley Urban National Park.
Photograph by Steve Russell, Toronto Star/Getty Images

“Without their natural enemy, they’re so good at spreading themselves everywhere and forming this monocultural environment,” says Dong. In essence, they choke out all the native species.

Dong hopes that with more time, researchers will better be able to understand how to fight invasive species within this ecosystem. In the meantime, the battle against them so far involves hand-pulling unwanted flora and repopulating the forest with native species.

Many such revitalisation efforts are community-led by Toronto residents such as Catherine Berka, who is part of the Toronto Ravine Revitalization Science community group. Berka and other residents restore ravines and educate homeowners on how to take care of the land, especially since around 40 percent of the ravines are on private land.

Exploring an urban forest

As local interest in the ravines continues to grow, the city hopes to make them a part of Toronto’s international identity. “A lot of the work that we’re doing to promote the use of the ravines to our own residents also lends itself well to tourists,” says Statham.

The city will spend the next decade improving ravines, building new trails and bridges, and planting more native species to lay the groundwork for long-term projects, such as the Loop Trail that will span Toronto.

A cyclist bikes through one of the dozens of ravines in Toronto.
Photograph by Carlos Osorio, Toronto Star/Getty Images

While several trails already exist, the complete loop will take users through nearly one-third of the city’s ravines and more than 20 of the city’s diverse neighbourhoods. It will also connect to and support the Meadoway, a continuous, multi-use trail that will become one of Canada’s largest urban linear parks and ultimately link downtown Toronto to the Rouge Urban National Park, the country’s first national urban park.

With more than 27,000 acres of ravines stretching across the city, there’s an experience for every type of traveller. One hike not to miss is the Lower Don Trail, a three-mile route that snakes north to south along the eponymous river. With multiple access points throughout downtown, it’s ideal for those who came for Toronto’s city life but want a quick escape into nature.

Rosedale Ravine Trail, which can be accessed at the corner of Yonge and St. Clair streets in downtown Toronto, takes adventurers under the city into a forest where sightings of red-tailed hawks, beavers, and other wildlife are almost guaranteed.

Scarborough’s Doris McCarthy Trail, about a half-hour drive from downtown Toronto, offers a moderate six-mile hike leading to Scarborough Bluffs, a towering cliff featuring picturesque views of Lake Ontario on Toronto’s eastern waterfront.

For something less crowded, Koa Thornhill, program manager at Park People, a group that mobilises Canadians to get into outdoor spaces, says Birkdale Ravine in Scarborough is well worth the trek. “It’s a little bit off the beaten trail, but it’s what I consider to be a hidden gem,” she says, especially in spring to see the rows of cherry blossom trees gifted by Sagamihara, Japan (Toronto’s sister city).

Josie Kao is a Canadian freelance journalist. Follow her on Twitter.


Explore Nat Geo

  • Animals
  • Environment
  • History & Culture
  • Science
  • Travel
  • Photography
  • Space
  • Adventure
  • Video

About us


  • Magazines
  • Disney+

Follow us

Copyright © 1996-2015 National Geographic Society. Copyright © 2015-2023 National Geographic Partners, LLC. All rights reserved