Our vision of urban infrastructure is often dominated by sights of towering skyscrapers. But the importance of trees has been increasingly at the forefront of urban planning. When confronted with the notion of not having as many trees, Torontonians can no longer picture their city in the mind’s eye.
Trees are a contributing factor in community development and growth. They improve neighbourhoods by reducing crime and heating/cooling costs. Trees lower stormwater management costs, fight soil erosion, and moderate temperature.1
The importance of trees can be measured, the structural value of Toronto's urban forest is estimated at $7.1 billion.1 The sense of identity they provide Toronto with and their ability to make the city seem more habitable, is harder to measure.
Approximately 10% of all trees in Toronto are Sugar Maples, the second most common tree and the most common deciduous species.1 The Canadian flag features the sugar maple leaf and its sap, when tapped and boiled, makes maple syrup. Unfortunately, it is illegal to tap a public sugar maple :(
A mature sugar maple will intercept 186,907 liters of stormwater, sequester 2,017kg of carbon, host moths/butterflies and is a pollinator for bees.2
They are sensitive to pollution and have deep roots. This makes them vulnerable in urban environments because they need uncompacted, draining soils.2
Sugar maples are amoungst the eldest of the trees of Toronto because they are indigenous to the region. The old sugar maples near parks had infrastructure built around them.
But arboriculture has advanced over the years. The practice of placing infrastructure has been replaced with incorporating trees at the planning and engineering stage of development.5
Hundreds of mature trees were fell to expand University Avenue into the 4 lane thoroughfare we know today.
The Avenue has been repopulated with indigenous trees, like the sugar maple, in an attempt to restore it to its previous canopy. The island of trees on University are in large concrete planters, so they can be moved about easily. While this method recognizes the need to have plenty of uncompacted, well-draining soil, it ignores the need for trees' roots' to congregate together.6
The felling of a tree is now a grievous offence in the city of Toronto. Councilors will fight for hours to protect the life of a single tree. And if a tree must fall, it has to be replaced with 4 more trees.
Exceptions are made though. In this particular case the sugar maple was too close to powerlines. If a tree is threatening powerlines, the structual integrity of a home, or is dead, council will allow the city or the owner of the tree to plant 4 new ones.7
60% of the trees in Toronto are on private lands. Over 100,000 trees have been planted annually since 2005 on public lands. In order to reach the target of 40% canopy cover in Toronto, private trees need to be planted and maintained.2
Behind this lovely sugar maple is a Tree Protection Zone. A TPZ is the area around the trunk, based on the size of the trunk, that protects the tree from any planned construction. Newly planted saplings will also require TPZ's, but are often small due to their trunk size.8
The mindset of city planners is now thinking in terms of green infrastructure and grey infrastructure. When developing any infrastructure project, planning will incorporate allowances for tree or shrub growth.6
With street trees, this new approach involves digging a continuous trench along the boulevard and filling it with uncompacted soil so the trees may grow together. Then there are slabs placed over the trench as to not compact the soil. The sidewalk is constructed on top of these slabs.5
Large areas of land that have infrastructure on them, are an opportunity to grow trees. The Dundas Bridge over the Humber is publically allocated land, but the bridge occupies the sky.
The importance of street trees cannot be understated when it comes to fostering community amoungst people, but parks are where trees foster community amoungst each other.
Trees planted near each other can withstand more threats than a tree on its own. Root systems relay information about insects and share minerals. Canopies protects trees from the damaging effects of wind. 9
The gilled mushroom, a popular variety in Toronto, emerge in the fall or warm winters, but live underground all year long. They are found in areas with rich, uncompacted, moist soil, just like the sugar maple.
These mushrooms pass carbon from tree to tree in exchange for minerals via the trees roots. This decentralized network also allows trees to ward off disease, fight against insects, and share resources.10
Accidental City, Robert Fulford, (1995)
Since the sugar maple loves uncompacted soil that drains well, they are often found propping up the banks of ravines. Their long, strong, deep roots are suited for the task. The ravines return the favour by providing the sugar maple with a fresh water supply and the loose soil they need to grow.
Toronto’s ravine system is the heart and soul of a remarkable natural environment system that spills out of the river valleys into the city’s parks, neighbourhoods and urban landscape.11
And like the roots of the sugar maple hold up the bank of the ravine, trees hold up the city of Toronto.