Tree canopy saves Nanaimo $13.7M a year, report says
Nanaimo’s tree canopy saves the city an estimated $13.7 million a year in avoided infrastructure, according to a new assessment presented to a council committee last week.
That’s an estimate of the value of the work trees do that would otherwise have to be paid for, from cleaning the air to absorbing stormwater and providing shade and cooling in hot weather.
When it comes to stormwater, trees can reduce runoff and soil erosion and improve water quality, especially when strategically planted, says the city-commissioned report, which was done in conjunction with Colorado-based urban forestry consultant PlanIT Geo Inc. and presented to the city’s governance and priorities committee meeting.
The dollar value of carbon sequestration alone — around 31,500 tons annually — was estimated at $367 million, and was assessed by looking at what it would cost to mitigate the impact of that carbon if it was released and not bound up in trees.
A canopy is the layer of branches and leaves at the top that shelters the ground from above. In this case, a tree canopy refers to the land covered by trees over 10 feet tall.
The report says that in 2025, Nanaimo’s trees covered almost 39 per cent of the city’s private and public land, up from the 33 per cent in 2016.
Much of the canopy increase came from growth of already-existing trees, but some was from new trees.
“I was really surprised by that one, obviously, because we’re an urban area and our reason for being, a lot of the time, is around growth and supporting growth in our region,” said Charlotte Davis, the city’s deputy director of parks and natural areas.
The report notes that development has put pressure on the existing canopy. Over that same time period, development caused the loss of tree canopy totalling about 84 soccer fields.
Putting the benefits of the tree canopy into an actual dollar value was useful, Coun. Hilary Eastmure said.
“Sometimes people just need to see the numbers associated with what we actually mean when we say the environment and the economy are intrinsically linked,” she said.
“The health of our environment directly contributes in a positive economic way to the sustainability of our city.”
Eastmure also pointed to the report’s finding that city-owned properties contain 19 per cent of Nanaimo’s urban forest, saying it emphasizes the direct role of the city in managing the health of its forest.
“That speaks to the need to continue to acquire more park land, and protect the trees that we have,” she said.
The report also highlighted the more than 500 trees in Nanaimo that are taller than 30 metres, and pointed out a few of special interest.
One is a 63-metre Douglas fir growing in Westwood Ravine Park that the report noted is “as tall as The Pacifica condominium complex in downtown.”
Others include a 41-metre Douglas fir beside the playground in Mansfield Park, and a 35-metre Douglas fir in Comox Park that reaches above the rooftops of the houses around it.
Cities should aim for a tree-canopy cover of at least 30 per cent or higher, the report notes. Some parts of the city, such as the downtown core and many roadways, currently have less than 20 per cent tree-canopy coverage.
“Our goal is for every neighbourhood within the city of Nanaimo to have 30 per cent canopy coverage,” said Davis.
jchadwick@timescolonist.com
And then there's this:
How much should a tree be worth? Experts say cities should consider climate-related benefits
Smaller communities in Canada are 'often struggling to put a good value on their trees,' says one expert
Along a street in Edmonton, mature trees sit protected by a green fence, near the construction of a new light-rail transit line. Signs affixed to the fence show the value of the foliage: A rosybloom crabapple tree is worth $1,389, while nearby a spruce is pegged at $2,185.
These price tags are somewhat of a common practice in Canada, where an assessment formula is used to determine the monetary value of a tree in case it is damaged or killed.
But forestry and biology experts say those dollar amounts don't fully capture the environmental value of trees in an urban landscape — especially as they play an increasingly important role in helping to deal with the effects of climate change.
"I think the monetary assessments are an important tool that we have, but we need to take them with a grain of salt in terms of what they may be capturing and what they may be missing," said Carly Ziter, an assistant professor of biology at Concordia University in Montreal.
Some of the benefits often unaccounted for, particularly in urban centres, include the cooling effect of trees and potential energy savings, their ability to capture carbon and their role in maintaining biodiversity.
Such aspects need to be assessed to determine a tree's true value, experts say, in order to encourage preservation of the current tree population — and to better protect the next generation of growth.
What's a tree worth?
Determining a tree's economic worth is not a new practice; municipalities and property owners typically turn to arborists or other experts for plant appraisal, and the value is determined based on several factors, including height, species, health and location.
Those factors are then used as part of a formula to determine a monetary amount in the event of an asset loss, as is done in Edmonton.
But the formula that Edmonton and many other municipalities use — The Guide for Plant Appraisal — doesn't yet include an environmental benefit element, said Jacqueline Butler, an arborist and project leader in the city's forestry department.
One of the reasons why Canadian municipalities use the guide's formula, and other similar appraisal methods, is because those values are defensible in court when there may be property disputes or other legal challenges, said Michael Petryk, director of operations with Tree Canada, a non-profit organization dedicated to planting and nurturing trees in rural and urban environments.
"The [courts] would view that tree as a piece of the property," he said.
"It's sometimes viewed as flawed, because it doesn't always take into account the environmental benefits that it would have. It's often just viewed as, 'How much is that single property owner benefiting from a tree?'"
Cecil Konijnendijk, a professor of urban forestry at the University of British Columbia in Vancouver, said it's time that more municipalities look beyond the dollar amount and take the time to more widely assess why trees are important.
Many smaller communities in Canada are "often struggling to put a good value on their trees," he said, suggesting that finding some easy-to-use methods "that actually show the true value of the trees" will be key going forward.
Some cities in Canada and elsewhere have already assessed the environmental value of their urban forests — taking into account things like how much oxygen is being processed by a tree or how it's helping with pollution, Konijnendijk said.
In Toronto, for example, the structural value of its urban forest is assessed at about $7 billion, with carbon storage alone valued at $25 million. That's on top of the $28.2 million in ecological services — things like air pollution removal, energy savings and carbon sequestration— that the urban forest provides annually, according to the city's 2021-2022 strategic forest management plan.
One of the ways municipalities are assessing that broader environmental value is by using i-Tree, a popular, peer-reviewed software suite from the USDA Forest Service. It helps organizations and city leaders understand how much a single tree or an urban forest removes carbon dioxide and air pollution, how it can help with stormwater run-off and other benefits.
Almost 8,000 Canadian organizations and municipalities have used i-Tree, according to its website.
Even still, Konijnendijk said, the i-Tree formula only captures part of the picture when it comes to assessing a tree's worth.
"We also have things like public health. We have things like biodiversity. Aesthetics. And those aspects are often much more difficult to quantify."
Why putting a value on trees matters
There are several ways trees can help cities deal with climate change, said Alison Munson, a professor in forest ecology at Laval University in Quebec City and a member of CRAUM, a research partnership into the city's urban forests.
The cooling effect that tree canopies can provide is extremely important and valuable, she said. In some cases, mature trees can cool down residential areas by several degrees, compared to streets without a similar tree canopy.
A 2019 study led by Ziter found that the right amount of tree cover can lower summer daytime temperatures by as much as 10 F.
There are other benefits, too, said Munson, particularly in urban settings: carbon sequestration as a tree grows, filtering out pollution and particulates in the air — and even buffering against noise.
Realizing these environmental benefits are not only important in the face of climate change, she said, but can also serve as a way for cities to balance densification.
"There's a push toward densification that doesn't always take very well into account the value of the trees," Munson said. "Cities have to take more responsibility toward taking into account these services that are so important."
Munson, Konijnendijk and Ziter all say ongoing monitoring of trees and long-term planning around our urban forests will be critical.
"It's not about tree planting as much as it's about keeping the trees alive. The average urban tree doesn't often get much older than 30, 40 years. So if you could double that lifespan, you would get a lot of ecosystem services," said Konijnendijk.
"That's where it starts: The good stewardship of the existing tree population and protecting the trees as best as we can in urban situations."
Ziter said researchers are currently looking at how the environmental value of trees may evolve over the years, as that, too, will be important for both current and future urban trees.
"For example, if we think about the benefits of a tree in terms of temperature regulation or flooding today, those trees may be even more important in a future that is hotter or that floods more often," she said. "Or maybe those trees will no longer be enough to provide that benefit in the future."
How we value our trees can't be a static approach, she said, noting such assessments should take into account the changes we expect to see when it comes to climate.
"Trees take a really long time to grow. In terms of practical applications, the trees we plant now are the trees that we will benefit from 10, 50, 100 years from now."
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