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Quality Soil Equals Healthy City Trees

by Richard J. Magill
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The trees in the City of Toronto’s urban forest are worth an estimated $7 billion, roughly $700 per tree, according to a recent study by TD Economics.

The report said the city’s urban forest provides residents with over $80 million worth of environmental benefits and cost savings each year. For the average single family household, that’s $125 annual savings.

As Citygreen® previously posted, urban forests do so much more than just beautify the area. Green space provides health, social and psychological benefits to its residents.

Using the City of Toronto’s urban forest as an example, TD Economics demonstrated how “an investment in urban forests is an investment in the overall economic and environmental well-being of urban society”. In the most populous city in Canada, there are 10 million trees of at least 116 different species.

“From a bird’s-eye view, these trees appear as a lush green canopy that covers nearly 30 percent (190 km2) of the City of Toronto. The density of Toronto’s urban forest is on average 16,000 trees per square kilometre or about four trees per person in the city. The majority of Toronto’s urban forest is located in its ravines and river valleys, such as the Don Valley, Highland Creek and Rouge River watersheds, which have been largely undisturbed by the city’s expansion.”

In recent years, there’s been an increase in recognition of the environmental and economic benefits of urban forests. Because of this, Toronto’s urban forest is “viewed as an investment in the economic and environmental wellbeing of the city”.

The report said that each year, Toronto’s urban forest intercepts around 25 million cubic metres of wet-weather flow. Urban forests intercept falling precipitation in their canopy thereby increasing the amount of water absorbed into the ground and reducing soil erosion. “The annual cost savings this provides through reducing burdens on processing infrastructure and mitigating damage is valued at over $50 million.”

As for air pollution, Toronto’s urban forest removes around one-quarter of the annual emissions produced by industry within the city. That’s about 19,000 metric tons of air pollution removed from the atmosphere each year. “The amount of particulate matter removed by Toronto’s urban forest each year is equivalent to the amount released by over one million automobiles or 100,000 single family homes.”

The report estimated that the amount of air pollution abated by the city’s urban forest generates an annual savings of $19 million – just under $2 per tree.

Trees can also reduce the energy consumption of buildings by providing shade, evaporative cooling and blocking winter winds. The annual net cooling effect of a young healthy tree is equivalent to 10 room-sized air conditioners operating 20 hours a day. Each year, Toronto’s urban forest generates $6.5 million in energy savings for businesses and households.

“Reduced energy consumption also avoids 17,000 tonnes of greenhouse gas emissions from emissions intensive energy sources each year, providing an annual savings of $400,000 to $600,000.”

The forests also sequesters over 46,000 tonnes of carbon, equivalent to the annual carbon emissions from 31,000 automobiles or 16,000 single family homes. Properties in Toronto near green spaces have also increased in value.

“Rental rates of commercial office properties are about seven percent higher on sites having a high quality landscape that includes trees.”

“Maintaining our urban forests makes sense, as every dollar spent on maintenance returns $1.35 – $3.20 worth of benefits to residents of the City of Toronto. The cost savings produced by our urban forests make it clear that keeping the green on our streets, keeps the green in our wallets.”