Ravines and resiliency: a nature-based solution to climate change

Did you know that Toronto’s ravine system is the largest in any city in the world? In fact, it’s so large that it’s been highlighted as a defining feature of the city, giving Toronto the nickname “a city within a park.” But these ravines aren’t just beautiful green spaces, they protect the city from severe climate impacts.

This system began to form around 11,000 years ago when the glaciers that once covered Toronto retreated northeast, leaving behind a landscape of rivers and valleys. Today, Toronto’s ravine system has a complex network of small streams and creeks, along with diverse geology, soil, flora and fauna, all working together to create a vibrant and dynamic ravine ecosystem.

Toronto’s ravines are a vital part of the city’s cultural heritage, playing an integral role in the lives of the Anishinaabe, Haudenosaunee and Huron-Wendat nations for centuries. Throughout history, the ravines have provided Indigenous peoples sustenance, a place for spiritual practices and pathways for trade and communication. They also reflect the traditional ecological knowledge of Indigenous communities who have a deep understanding of the delicate balance of this ecosystem.

Evergreen and the ravines

Evergreen has a deep-rooted connection with Toronto’s ravines. From our earliest activities with tree planting in the Don Valley to our work on the Loop Trail to our celebration of the ravines during Ravine Days, we understand the importance of this vital ecosystem to our cities.

We even made the ravines our home back in 2010 when we transformed a collection of deteriorating heritage buildings into a community hub, Evergreen Brick Works, which has become an access point to the ravine system for Toronto. Today, we’re lucky enough to share the ravines with animal friends like turtles, beavers and frogs, and run beloved community programming, like camps, public markets, tours and events in this space.

The importance of ravines to our cities

So, maybe you’re wondering: why are ravines so significant? Well, they’re a vital city asset that provides a number of important ecological services such as:

• Creating critical habitat for wildlife: The biodiverse vegetation and varied terrain of ravines makes it the perfect home for birds, mammals, amphibians and insects.
• Water management: Ravines help manage stormwater by capturing and slowing runoff, reducing the risk of flooding and erosion. Their dense vegetation also helps to filter pollutants from water before they make their way to larger bodies of water.
• Reducing urban heat: Ravines manage air temperature by providing shade from trees, cooling the air through evapotranspiration, facilitating better airflow and reducing heat absorption.
• Mitigating the effects of climate change: Trees and plants in ravines absorb carbon dioxide in the air and store it in their biomass and soil, which reduces quantities of greenhouse gases (GHGs) in the atmosphere.

Ravines as nature-based solutions to climate change

Nature-based solutions (NbS), like ravines, are critical in dealing with climate change. NbS are strategies and actions that protect, sustainably manage and restore natural processes and ecosystems to address climate change and its impacts. Examples include reforestation, wetland restoration and the creation and protection of urban green spaces like parks and ravines.

While technological climate solutions such as solar panels, wind turbines and heat pumps are effective in reducing GHGs in the atmosphere, prioritizing nature-based solutions helps to protect our cities from increasingly frequent and severe climate impacts with minimal upfront and operating costs.

A recent example of this is how the surrounding ravines played a crucial role in water management during the flood in Toronto on July 16. The ravines acted as a natural reservoir and held excess water; they reduced the volume of runoff that flowed into downstream areas; and their soil and vegetation improved water infiltration. The impacts of the flood in the city would have been much worse if it weren’t for this natural climate solution.

Reviving the ravines

Many of Toronto’s ravines are under threat from urban development, population growth, invasive species, pollution, erosion and extreme weather events. In 2017, Toronto adopted a 10-year strategy to preserve and manage the ravines. Ongoing efforts, including the rehabilitation of degraded areas, the controlling of invasive species and the replating of native vegetation are showing signs of success.

Ravines are critical to not only providing climate resilience, but also offering numerous social benefits that improve the quality of life for residents. They create a network of trails that connect various neighbourhoods in Toronto, encouraging active transportation like walking and biking. They’re also locations for community events, family outings and picnics and their natural beauty offers an escape from the bustling city environment.

Toronto’s ravines offer a valuable opportunity to plan our city in harmony with nature, allowing us to prepare for the effects of climate change alongside these natural features rather than working against them. By creating climate-ready spaces in our cities and incorporating nature-based solutions, like ravines, we’re helping to ensure that beloved public spaces in our cities, like Evergreen Brick Works, are resilient and can exist for generations to come.