Why Urban Trees Are Giving Us Life
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Why Urban Trees Are Giving Us Life

In Toronto, trees provide $28.2 million worth of services each year in the form of savings on heating and cooling, improvements to air quality and carbon sequestration.

Public Works looks at public space, urban design, and city-building innovations from around the world, and considers what Toronto might learn from them.

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People taking pictures of cherry blossoms in Toronto’s High Park on April 24. Photo via Instagram

Each spring, Toronto changes colours as cherry blossoms emerge and leaves begin to unfurl. Almost overnight, trees become the subject of countless photos and a source of shade. But trees act as more than just Instagram photos or patio décor.

In cities, trees provide habitats for wildlife, contribute to pollination, and intercept runoff after it rains. Although the majority of urban trees are located on private property or in parks, street trees also add to quality of life.

Trees planted along sidewalks and beside roads encourage active transportation and create positive pedestrian experiences by blocking noise and pollutants. By sheltering buildings, street trees also reduce heating and cooling costs.

Street trees are an especially important source of greenery in dense urban areas. In fact, since lush green spaces are associated with higher property values, street trees are a tool for spatial equality and a way to introduce natural features to neighbourhoods lacking parks and outdoor amenities.

Despite these advantages, street trees struggle to survive. Surrounded on all sides by concrete, street trees face challenges of soil quantity and quality. Urban soil is often compacted, making it more difficult to establish a root system, while construction and other activities change soil composition and introduce contaminants. Plus, although they shield people and places, street trees are exposed to high winds and extreme temperatures.

9056623850_7a23ee0db0_z Photo by Ashton Pal from the Torontoist Flickr pool


All of this is to say that street trees are up against additional pressures compared to their cousins growing in public parks or private yards. Research into the mortality rates of street trees is limited but urban ecologists agree that these trees are most likely to die during the first few years after planting. According to one study, the mortality rate is almost four times higher among the smallest trees.

Urban Releaf is a non-profit in Oakland, California, that plants trees but also maintains them in these crucial early years. The organization was founded in 1998 in response to the lack of both trees and youth employment opportunities in the West Oakland neighbourhood. Since that time, the organization has planted more than 15,000 trees across the city.

It also trains and employs young people to look after the trees for the first three years after planting. In this way, the organization increases the chances of survival of street trees, creates jobs, and empowers champions of the urban forest.

tree_diagramPhoto from Urban Releaf.

Urban Releaf’s approach is intentionally intersectional: its Urban Forest Education and Stewardship Training program covers twelve topics ranging from tree anatomy to civic engagement and environmental justice. This work is rooted in the recognition that in Oakland, as in other cities across North America, low-income neighbourhoods are home to fewer trees and green spaces.

Urban Releaf’s activities have become all the more important in the past decade. Although in 2007, the City of Oakland identified 46,624 street trees, more recent data is not available because almost half of the city’s tree services were eliminated the following year. In the absence of municipal tree planting, watering and pruning, Urban Releaf and other local non-profits are on the frontlines of protecting and enhancing ecosystems in the third largest city in the San Francisco Bay region.

14018763789_8191eb6b3d_z Photo by Bruce Reeve from the Torontoist Flickr pool

In Toronto, municipal forestry services care for 600,000 street trees, which represent six per cent of the 10.2 million trees in the city. Although Oakland tried to save money by eliminating forestry services, a study [PDF] of Toronto shows that trees provide $28.2 million worth of services to the city each year in the form of savings on heating and cooling, improvements to air quality and carbon sequestration. Figures like these demonstrate that urban forestry is a worthwhile investment and strengthen the case for acknowledging trees as an essential component of a city’s green infrastructure.

Yet even in Toronto, street trees face harsh conditions. The same report indicates that although 81 per cent of Toronto’s trees are rated as being in good or excellent condition, the same can be said of only 49 per cent of the city’s street trees.

In this context, Urban Releaf confirms the value of maintenance in the first few years after a tree is planted. However, the organization’s prominent role in both planting and watering also offers a cautionary tale of what happens when local governments cut support for urban ecosystems.