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Urban forest needs help, should be regarded as vital infrastructure: report

Trees are civic infrastructure, just as necessary to the smooth functioning of the city as are highways, storm sewers and transit lines. And just as built infrastructure tends to be better in wealthier neighbourhoods, trees too are more plentiful and better cared for in those same neighbourhoods, a state of inequality that can result in far-reaching social costs. Policy makers at all levels need to acknowledge the importance of trees and do more to expand Toronto’s urban forest, making trees a key part of planning and of climate change policies.

So says the first ever report of its kind on Toronto’s trees, the “State of the Urban Forest” report, which was released by a coalition of agencies under the name Green Infrastructure Ontario Coalition. The report is based on studies conducted by various municipalities and conservation authorities in the GTA from 2005 to 2014. It was released at the Grey to Green Conference being held at Ryerson University.

The report makes the case that trees—the urban forest—are much more than decorative accessories that dot our parks and improve the view here and there. Rather, the forest is a “vital asset” that helps to cool the city in extreme heat as well as reducing the heat island effect and helping to prevent flooding.

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Source: State of the Urban Forest in the Greater Toronto Area

Trees improve public health. The GTA’s approximately 34.2 million trees remove nearly 4,000 tonnes of atmospheric pollution annually, more than half of that being ground-level ozone. Ozone is a main component of smog. Researchers have found “clear connections” between urban forests and a whole range of health benefits: improved concentration levels, stress reduction, lower risk of depression, better cardiovascular health and even stronger communities.

The urban forest supports climate change mitigation efforts by absorbing and storing carbon dioxide. The cooling effect of shade trees can offset the demand for air conditioning in summer. The same trees serve as windbreaks in winter. In each case, they can offset demand for energy to heat and cool buildings, and reduce the associated greenhouse gas emissions.

Toronto’s forest is currently dominated by just a few species of trees. Maple trees are the most abundant by far, followed by cedar and ash. Sadly, the ash trees are under attack by the emerald ash borer, which is expected to kill up to 3.2 million of the trees. Planting a greater variety of trees would increase the biodiversity of the urban forest, and help offset losses to one species. Replacing all of the trees and shrubs now growing in the GTA would cost an estimated $14.2 billion.

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Source: State of the Urban Forest in the Greater Toronto Area

The report shows that just 3 per cent of Toronto’s trees today are elms, once one of the most common city trees in North America. A single large tree such as an elm or maple can store up to sixty-five times more carbon and remove fifteen times more air pollution than smaller trees. However, 85 per cent of the trees in the GTA are in the smallest size category, while a mere 1 per cent are in the largest. The report recommends that 10 per cent of trees should be of the largest kind.

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It would cost an estimated $14.2 billion to replace the GTA’s 34.2 million trees.

Most of the trees in the city are on private residential lands. This is a good thing because these trees have a better chance of flourishing. It is far better for a tree to be on a lawn than in a concrete planter in the middle of a busy roadway. Nevertheless, we want to see trees on downtown streets, and indeed their presence in the heart of the city is beneficial. Urban planners and designers will have to do a better job of giving trees what they need to thrive: better soil quality and more of it, water, space, and regular maintenance. The report maintains that protecting existing trees may be the most effective strategy for reaching its recommended canopy cover targets. This would require targeted programs that support homeowners and tenants in caring for their trees.

Environmental equity

This leads to the question of “environmental equity.” There are “have” and “have not” neighbourhoods, the report says, when it comes to trees. High-income neighbourhoods have greater tree coverage than low-income neighbourhoods. Since tree coverage is associated with physical and mental health benefits, this inequity of tree distribution is reflected in the relative health of the communities. Unfortunately, the daunting problem of social inequality is beyond the scope of this report, and it can do no more than suggest that “we can try to better understand the social and political roots of the problem,” and prioritize tree planting in communities that need it most.

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Wealthier neighbourhoods tend to have more trees than poorer neighbourhoods, a fact that is reflected in the health of the respective communities.

The report concludes that a sustained effort will be needed to grow the urban forest, and it urges “each governing body” to identify ways to support it. Its four main recommendations are

  • Develop and enforce strong policy and legislation
  • Invest in green infrastructure
  • Empower community members
  • Support research and monitoring
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