The past year was inarguably a stormy one for Torontonians. In addition to the unprecedented maelstrom at City Hall, July's #FloodTO dumped an estimated 61 billion litres of rain into the city's streets, subways, yards and basements, just in time for rush hour. In December, #IceStormTO capped the city with an eerie, icy coating that downed an estimated 20 percent of the urban forest canopy and left more than half a million Ontarians in the dark during the busy holiday season. The ground then literally exploded during a cold snap the next week.
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So, can we expect more frosty madness? And what can we do to better prepare for the storms ahead — and help restore the urban forest? Below are five things you should know about trees in the city and ice storms.
1. Can we expect more ice storms? Although much of North America is in the midst of a severe deep freeze this week, climate change is expected to cause warmer winter temperatures across the country. This will likely increase the frequency and intensity of severe freezing rain storms and wet snow, which can damage trees and overhead wires and cause major power outages, as in eastern and central Canada in 1998 and this past December.
2. Why do trees fall in an ice storm? When super-cooled rain droplets land on a cold surface like a tree branch, they freeze on contact. Deposits of dense and often transparent layers of ice dramatically increase the weight of tree branches. The amount of damage to a tree depends on a variety of factors, including the type of tree species, the health of the tree, how much ice accumulates and exposure to strong winds. For more about why trees fall, check out Margaret Bream's insightful column on the subject. Trees are the living green infrastructure of our cities, providing countless benefits like shade, privacy, windbreak, cleaner air and livable neighbourhoods — just to name a few. But just like all infrastructure, our urban forest needs to be maintained so that it can continue to provide us benefits.
3. Can we prevent trees from being harmed by ice storms in the future? Early estimates suggest a loss of up to 20% of our urban canopy in Toronto, but it will take some time to fully assess the damage. Whatever that number proves to be, this is without a doubt a devastating loss of trees. We can never prevent all damage to the urban forest during ice storms. But we can be more prepared by ensuring that mature trees are inspected and proper corrective pruning is being done every three to five years in order to remove weak branches proactively. This needs to be determined on a case by case basis for each individual tree. The key is that people need to know how to hire a qualified professional that will provide a proper assessment, corrective pruning and ongoing care prescription. LEAF provides tips on how to hire a qualified professional. Ensure anyone working on your trees is a certified arborist and that they have adequate liability insurance. Never be rushed or pressured into "bargains." Check out this Torontoist story for more information.
4. What can homeowners do about existing trees in their yards? Planting a greater diversity of species, including more storm-resistant ones like conifers, and planting more trees in spaces where there is more room and fewer power lines, like backyards and commercial properties, will also help. LEAF offers native trees to Toronto and York Region property owners at a subsidized cost and provides advice about the type of tree that best suits the property. The program includes a 30-minute yard consultation with an arborist, a 5 to 8 foot tall tree and full planting service, all for as little as $150. Native shrubs are also available. And be sure to treat your existing trees with tender care — they need regular watering and mulching, so that they have the best chance of surviving summer droughts and winter storms.
5. What trees are best? Getting the right tree in the right place is key. Hardy, native tree species are best suited to our climate and also provide essential habitat for wildlife. Each yard is different with unique soil composition, overhead and adjacent obstacles, water supply, wind speeds and available sunlight. It's important to consider these physical conditions as well as other goals such as shade, privacy and fall colour. LEAF offers a variety of native species through the Backyard Tree Planting Program, and will conduct a site visit to help you select the most suitable trees for your yard. You can browse through the photos of the many species available.
They are both steering committee members of the Green Infrastructure Ontario Coalition.