What's the value of a tree? The city will tell you

They're leafy, shady,and in some cases come with a whopping price tag the City of Calgary has assigned a value to most trees on public land.

But anyone who is looking to fell one of those trees might wonderhow that value is assessed.

There areabout seven million public trees in Calgary with a collective value of $1.3 billion.

The practice of assigning value to a tree is somewhat common in Canada, where an assessment formula is used to determine the cost of a tree in case it is damaged or killed.

LISTEN |How the city decides which trees are worth $500, and which are worth $50,000:

Calgary Eyeopener7:39Assigning value to public trees

How the city decides which public trees are worth $500, and which are worth $50,000 or more.

Mike Mahon, urban forestry lead for the City of Calgary, saida tree's cost in Calgary is calculated by urban forestry technicians who look at a tree's structure, health, species and most importantly, its age and size. Those figures are then put into an algorithm that generates a monetary value.

Mahon said on the Calgary Eyeopener that the city's most valuable trees are often located in older neighbourhoods, particularly along the river valleys.

• Calgary is a city of haves and have-nots when it comes to trees

The city's formula is derived from the Guide for Plant Appraisal, which is used by many municipalities across North America.

That results in price tags from $500 for a quaking aspen in Hidden Valley to $180,000 for a Scots pine in Britannia.

A tree's price is seen by the city as a way to retain trees and protect them from construction and development.

"Trees provide so many different values and benefits, whether it be social, environmental or even economic. I think what resonates most with people is monetary value. And so the reason for valuing trees is to highlight their importance," Mahon said.

If development occurs on a lot with a tree, the city will propose design changes to protect and retain the tree.

However, if design changes are not possible, the city can authorize the removal of the tree and the value paid will be used to plant new trees.

WATCH| Learning about tree cover in Calgary:

How does Calgary stack up when it comes to tree cover?

2 years ago

Duration 5:58

Some neighbourhoods in Calgary have an abundance of trees while others are sparse. Who are the haves and the have-nots when it comes to tree canopy?

Calgary's algorithm does not factor in a tree's environmental impact. CBC has previously reported that some experts feel environmental impacts should be assessed, including the cooling effect of trees and potential energy savings, their ability to capture carbon and their role in maintaining biodiversity, in order to determine a tree's true value.

Bev Sandalack, a professor of planning and landscape architecture with the School of Architecture and Planning at the University of Calgary, said a dollar value helps people understand that trees aren't just decorative.

"They have actual value. They cost a lot of money to install, but the values that you get from trees far outweigh what the initial cost would be," she said.

But she added that trees also have value that's hard to put a dollar figure on.

"I could see the ecological value, the psychological value, the visual value, the impact that trees have on mitigating or helping in many ways with climate change. So those things are very difficult to assess."

Mahon said the city's tree strategy will be rewritten within the next couple of years.