Matthew Higginson's picture
Posted by Matthew Higginson /
Rock salt hurting our urban forest
Salt. It's on our tables, in our food and on our sidewalks. It has been linked to high-blood pressure and cardiovascular disease in us; discoloured leaves and sparse foliage in our canopies overhead. And as pressure grows to get Canadians to ease up on our intake, it may also be time to put our trees on a low-sodium diet.



Sure, they can be easy to forget when their bare branches don’t offer much. While they can be a spectacular sight after a snowfall, the impression quickly fades. I’m quickly back to counting the days until spring. But with our recent mild winters, it can be hard to figure out what to wear, much less how much salt to throw down on our streets - and that is a problem.


According to Carly Weeks piece last month in the Globe and Mail, the average Canadian “consumes more than double the recommended amount.” But compare that with Toronto's urban forest - which absorbs mountains of salt each year – up to 150,000 tonnes from city trucks alone. As groups like the Canadian Medical Association, the Heart and Stroke Foundation, Hypertension Canada and the Canadian Stroke Network call on Mr. Harper to take action on plates, we ought to call out for action on our streets.


Trees' moisture is drawn out by the salt spray of passing vehicles. Their roots are damaged as salt water is absorbed into the ground, affecting microbes and altering the nutrient makeup of the soil. Imagine waking up after a long sleep to find your bedside supply of water filled with salt.


When our cities go through this thaw-freeze-and-repeat, the excessive salt on our streets and walkways - put down by concerned store owners and citizens - gets carried along paths and ravines down to the lakes and rivers we hold so dear. It soaks into the ground and hurts the very plants we are waiting to enjoy. Obviously this is a mistake that needs amending.


Milne Hollow


After all, who doesn’t want to live in a green city? As the weather changes, take note of the trees near the sidewalks, driveways, and front steps. Remember them. Evergreens tend to be particularly sensitive, but consecutive years of salt damage can weaken even our toughest trees and vegetation.  Like us, all living, breathing, things require a fine balance to stay healthy. These urban fixtures are no different. 


Our educational tree tours touch on many of the urban stresses that our trees face, and our Tree Tender Volunteer Training Program offers hands on training for ways you to help your neighbourhood thrive. My own way of seeing has been shaped in part by the arborists, experts and instructors that lead these uniquely catered programs.


When it snows, pick up a good shovel rather than waiting with a bag of salt. Get a work out, help work off some of that sodium in your own diet and help your neighbourhood trees. Use environmentally-friendly de-icers, and apply it before any ice has time to form. You’ll also be glad to know that the City of Toronto is aware of the risks of road salt to the environment and that they are working to find the right balance as well. 


Rock Salt in Toronto


We all want to make our sidewalks safer. But think of the dogs' paws and trees' roots - even the grey infrastructure that gets eaten away! On behalf of the things that can't speak for themselves, we could all stand to make a conscious choice about how much we really need. As the old axiom goes, when the weather changes, people forget how to drive. We should probably stop overreacting at the first sight of snowflakes as far as salt goes too. Think of it as a first step towards getting our urban forest on a healthier diet.



Back in November LeasideTrees was created to rally community support to understand why a permit was issued for the destruction of a giant Silver Maple that had been deemed to be structurally and botanically in fair condition. The response from the local Councillor was that city policy was followed. A list of more than 60 residents was forwarded to Councillor Parker and rather than addressing the questions, he simply repeated that policy was followed. Being published this week is a front page article on the Silver Maple in the local community newspaper Leaside Life. Urban Forestry according to the article did not return their calls. We continue to ask Councillor Parker to address our questions and our request for an inquiry into why a permit was issued.
Thanks for this - do you have a link to the article? I've been following your fight for the silver maple and I'd love to read the piece.
Great post! This is such a neglected environmental issue. Most people now indiscriminately use salt for for de-icing, not even realizing how toxic it is to both vegetation and aquatic life in the Great Lakes (where most of it ends up). It's good that the city has a salt use policy, but it seems to me that the worst offenders are lawsuit-fearing businesses and property managers. Maybe a solution would be a statutory negligence defence to slip-and-fall lawsuits for people who, in good faith, reduce or eliminate their salt use while maintaining a reasonable standard of safety in other ways.

Interesting take, Raj! It is totally a neglected issue in this city and I'm glad you brought up the point that it all leads down to our lakes. It's about time we collectively worked harder at connecting our lifestyle choices to what we can live with -- because toxic winters can make for gross beaches come summertime... and who wants that?

As for businesses, I can see their predicament and my message to them is "reduce, reduce, reduce."  Premptive salting, oversalting and a general lack of understanding about how it works and its affects can really harm our infrastructure, our waterways and the precious wildlife that rely on it.  The more we talk to the businesses we frequent, the more we can bring them over to the idea that less is more, and environmentally-friendly alternatives are out there....Thanks again!


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