Combatting Urban Tree Canopy Decline: A Guide for Homeowners
Walking through a city used to mean wandering under the cooling shade of towering trees. But now, those canopies are thinning – especially in Toronto. Urban Tree Canopy Decline is more than just losing patches of green in our concrete jungles. It means hotter streets, poorer air quality, and missing out on the quiet moments nature offers amidst urban hustle.
Mitigating Urban Heat Islands
In cities, trees act as natural air conditioners and can reduce temperatures by as much as 6°C. This is important in Toronto and the north. While people living in more southern areas have adapted over time to extreme heat, in Toronto and across Canada there was less need to do so.
Because of this, air conditioning is less widespread, and structures built to withstand harsh winter haven’t been optimized for hot, hot summers. Trees help fill this gap by providing shade and cooling the surrounding air.
Trees in cities help reduce heat by absorbing sunlight during the day and releasing it at night. This phenomenon is known as urban heat islands. Urban heat islands are caused by concrete absorbing sunlight during the day and releasing it at night. Trees play a crucial role in reducing the heat caused by urban heat islands in cities.
Toronto is called a “City in a Park” because it has lots of green spaces. This helps to reduce the effects of climate change and rising temperatures. To make this happen, we need to protect and grow more trees in the city.”
The Decline of Urban Tree Canopy Cover
Urban tree canopy cover is on a downhill slide, and it’s not just about losing the shade. Cities are facing a tough challenge as the dwindling tree canopy not only complicates city planning and energy consumption but also worsens air purity.
Tree Canopy Impact on Energy Demand
When the leafy shields over our cities thin out, we feel it – literally. As the number of trees decreases, people rely more on their air conditioning, causing an increase in energy usage. Using AC more often costs more, and is not an option for some people or organizations.
The Toronto District School Board has a repair backlog of $4.2 billion. This backlog has prevented the board from installing air conditioning in every school. This can leave adults and children vulnerable to the heat.
At the same time, fewer trees worsens air pollution, creating an even larger and longer term health hazard. Everyone must work together to understand the importance of urban forests. They should also include them in city development plans in order to make a change.
Homeowners play a crucial role in making Toronto liveable for everyone. How?
Residents Have a Voice in Urban Forestry
Homeowners, business owners and residents of Toronto have a say in what happens in the city. Supporting Urban Forestry laws, tree planting and calling for tougher standards could have a big impact on tree cover in Toronto.
Cities like Mississauga have already improved their tree protection by ensuring that they protect all trees over 15cm DBH. That is half the size of the current Toronto by-law. In Oakville, arborists must register for a business license with the city to prevent illegal tree cutting by untrustworthy operators.
Finally, residents in Toronto and beyond could push to make Arboriculture a restricted trade like electricians. This means that instead of anyone being able to pick up a chainsaw and cut down a tree, you’d need a license. Actions like this would protect our urban forests on a number of levels and reduce the number of injuries and deaths that occur every year in the tree care industry in Ontario.
Pests Threatening Urban Trees
Recent years have seen a spike in insect populations, largely due to milder, wetter summers brought on by three successive La Niña events. The surge in insect numbers poses a grave threat to the vitality of trees in the City.
Now, we have El Niño to contend. In 2024, temperatures are expected to be much higher than usual. There is also a higher chance of extreme weather events happening. Additionally, sudden changes in the forecast are more likely to occur. Big, fast storms cause huge amounts of damage to trees and increase the risk of pest infestations when they are damaged.
Warmer temperatures can cause more pests, diseases, and fungus to affect trees. Some examples include maple tar spot, powdery mildew, aphids, and spider mites. These issues can harm trees by draining their life force.
Emerald Ash Borer and Oak Wilt
In the past few decades, Emerald Ash Borer decimated the population of ash trees across North America and now new threats are on the horizon. Oak wilt is travelling north at a rapid rate and many believe it to already be in Toronto. This fatal disease could cause a massive crash in the Oak tree population in the city. As a fungal infection spread by boring beetles, there is no cure.
The beetles are dormant during cooler weather, so a warmer spring and longer summer extends their activity period and the threat they pose to Toronto’s Oak trees.
Many pests, pathogens, and fungus can stress trees, leading to death or decline. This can happen even if the tree is not immediately killed. Various factors like drought, pollution, and disease can also contribute to a tree’s demise over time. Understanding these factors can help in preventing and treating issues that may arise.
The Importance of Arborists
Certified Arborists from reputable companies are on the forefront of protecting Toronto’s urban canopy. Tree care is a science, an art, and a practice. Taking care of trees involves understanding tree biology, using heavy equipment for pruning or removal, and improving their appearance. This includes knowing how trees grow, operating machinery for trimming or cutting down branches, and making them look more attractive.
Improper Pruning Harms Trees
Improper pruning can seriously harm or kill trees. When pruned incorrectly, trees can become more dangerous or damaged to the point of needing to be removed. Tree service professionals in Toronto work hard to keep trees healthy and strong by using the best practices and safety standards.
Impact of Tree Removal – both legal and illegal
Sometimes, trees need to be removed. The City of Toronto Urban Forestry department manages the permit process to approve or deny tree removals based on the tree’s health and safety.
Reputable companies won’t illegally remove trees that require permits, and will work with you to understand the process and find other solutions if necessary. When it is necessary to remove a tree, doing so safely and without damaging nearby trees or greenery is a part of supporting and respecting the local environment.
When trees are removed illegally, or damaged by incorrect pruning, the costs can be huge. Homeowners may be fined, but more so, the environmental losses from this practice have a big impact on our local communities.
Consider how hot Little Italy is in comparison with Riverdale, or Yonge and Eglington vs. mid-Etobicoke! The coolest areas of the city are also the most affluent, like Rosedale and the Bridle Path due to the presence of both private and public trees. The difference in heat is measurable and significant in the height of summer, and it’s all due to trees. When private trees are cut down illegally in our city, it impacts everyone.
Partnerships to increase Canopy Coverage
Reversing the decline in tree canopy cover necessitates a united front, blending efforts from private tree companies, City Urban Forestry and homeowners to ensure we maintain enough urban canopy in the city.
Benefits of Trees Beyond Cooling
Trees do more than just provide shade on a sunny day. In the concrete jungles we call cities, trees stand as bastions of health and mental solace, offering much more than a mere respite from the sun’s glare.
When trees are stressed due to lack of water, they may shed their leaves prematurely. This not only reduces the cooling effect through shade but also diminishes their ability to cool the air around them through transpiration.
The following are examples of what are called some of the “social determinants of health“, or what makes people more or less healthy that exists in their environment or society they live in.
Health Impact of Trees
Let’s talk numbers for a second: did you know that being surrounded by trees can actually lower your blood pressure? It’s true.
There have been many studies that attest to how being in green spaces like parks, forests or simply looking at trees from your house windows, can reduce stress and improve well-being. The wellness advantages of trees are significant.
Being able to relax, rejuvenate or play in and among trees improves the lives of people. Trees can also benefit human health in other ways:
- Reducing depression, anxiety and improving mood
- Lowering blood pressure and decreasing risk factors for cardiovascular disease, stroke and other ailments
- Reducing risk factors for chronic diseases and cancer
- Reducing risk of heat exhaustion and death from heat
Steps to Combat Urban Tree Loss
Tree Preservation is the first step
Tree maintenance is a part of homeownership, but it is also a part of environmental stewardship. Trees in cities grow differently than those in forests, and are under tremendous stress from pollution, drought, pests, damage to roots/trunks/branches, lack of nutrients in the soil and more. The difficult growing conditions are hard enough for existing trees, let alone new plantings.
Proper tree pruning is important to maintain their health. With an abundance of sun, trees in cities can grow very quickly – but they are also susceptible to damage from extreme weather, pre-existing rot and other issues. In a forest, a branch breaking is inconsequential, but in the city, it can have disastrous consequences.
Properly pruning trees can address hazards, improve health, and extend the life of trees that might otherwise need removal. Cutting down small or unhealthy big trees can benefit their neighbors. It can stop the spread of disease, let in more sunlight, and reduce competition.
There are many choices available. It’s important to ask a certified tree expert for their opinion. The expert should be from a trusted local tree company.
Choose the Right Trees for Your Area
Finding trees that thrive in urban conditions can be difficult. To help you out, many cities have compiled lists of recommended species.
The City of Toronto’s Urban Forestry Division helps people choose the right trees for planting in streets and parks. They provide information on tree types that are suitable for different locations. This includes streets and natural areas in parks.
The division offers guidance on selecting trees that will thrive in these environments. The city also offers grants and incentives for tree planting to help increase the number of trees in Toronto. The Toronto Region Conservation Authority also has funding for homeowners to improve tree coverage.
Support Local Tree Planting Initiatives
You don’t have to be good at gardening to volunteer. By participating in community tree planting events, you can greatly increase the amount of trees in your area.” These initiatives often target regions lacking canopy coverage, aiming to plant trees that will grow into healthy adults.
You can help plant or care for trees in the Greater Toronto Area. You don’t need to be a professional arborist to get involved. There are many opportunities available.
Here are some volunteer opportunities for getting involved in greening initiatives:
- City of Toronto Spring Tree Planting 2024 – Tree Planting Captains
- Volunteer to plant and care for trees with LEAF for spring 2024 in Toronto
- The Toronto Region Conservation Authority (TRCA) has many different volunteer opportunities to do with tree care, tree maintenance and tree planting
- 10 000 Trees for the Rouge plants trees in the Rouge Valley and other locations
- Credit Valley Conservation hosts clean up days and tree planting
Homeowners play a significant role in Tree Protection in Toronto
Tree care in Toronto is paramount to ensuring that our canopy coverage grows. About 60% of all trees in the City are on private property – about 6.1 million at last count. The rest are on the city streets (6%) or city parks and ravines (34%). Homeowners and businesses play a huge role in ensuring there are enough trees around the city to keep temperatures cooler, clean the air and help filter water run-off.
During sunny weather, paved areas can experience temperatures that are 27-50 °C higher than the surrounding air. The temperature difference is most noticeable at night. The heat absorbed by pavement and buildings during the day continues to raise the city’s temperature. This happens even after the sun sets. In the evening, urban areas can be notably warmer, up to 12 °C, compared to their neighboring environments.
The Greater Toronto Area is expected to see a surge in extreme heat events, escalating from 20 days annually to 66 days annually by 2050. This rise in temperature poses a heightened threat of heat-related illnesses and fatalities.
All of the health and environmental factors that we discussed above are more impacted by what individual property owners do as a whole than anything in particular the city does to city-owned trees.
Help Stop Urban Heat Islands and Mitigate Urban Tree Canopy Decline: 10 steps for City of Toronto residents
Start gardening or planting at home and at work. Planting trees, hedges and shrubs helps to reduce the heating effect of hardscape like pavement, asphalt and stone. When the sun shines down on a city street in the summer, the road material absorbs the heat and holds onto it, warming the area for a long time after the sun goes down. Trees, shrubs and hedges reduce the amount of hardscape, retain moisture and have a cooling effect.
Avoid installing hardscape like stones, rock, pavement, patio tiles and asphalt. If you must install a firm surface, try wood decking.
Ideally, however, keep your grass or install a new lawn in your front or backyard to decrease heat and support the health of other plants. Since trees, shrubs, hedges and flowers all rely on water, when you put hardscape over their roots the have significantly less access to it. This means they can suffer drought and stress even in heavy rain, as the water washes down the pavement into the sewer.
Prune your trees and maintain them to keep them healthy. Tree maintenance is far more cost effective that tree removal, and when it is done at regular intervals it becomes even more cost effective than waiting until the situation is dire. Healthy urban trees are far less susceptible to diseases and much stronger in the face of ongoing storms.
Remove invasive species before they take over an area ands plant native species. Toronto’s ravines and public green spaces have been overtaken by trees like the Norway Maple and Tree of Heaven. These non-native trees outcompete native species.
In the Beaches area, oaks are under threat due to the spread of Norway Maples as the Norways are shallowly rooted, suck up available water and die relatively quickly in comparison to the lifespan of oaks.
This means that greater erosion in ravines happens, and oaks become more stressed due to the competition for limited resources. When this happens, they can enter a decline spiral. On your own property, you may notice Norway Maples growing very aggressively and shading out other plants and trees.
While Norway Maples can be valuable for their dense canopy and quick growth, they aren’t a sustainable solution. We need trees that can last in the City and contribute ecologically.
Install Mulch around tree roots (but not right at the base!) to help trees retain moisture from rainfalls and to further absorb heath and keep the ground cool.
Install watering spikes to help water trees more efficiently. Unlike grass, trees need long “drinks” but less frequently. Water 1-2 times per week for a few hours can immensely support tree health. Instead of using a soaker hose or a sprinkler, which are not very water-efficient, you can choose inexpensive water spikes. Simply install the water spikes and attach your hose for easy watering. Simply install them and attach your hose for easy watering.
Support local tree laws! Support local arborists! Support trees!
Tree canopy loss is significant. This means: don’t illegally remove trees or injure them, and call the City of Toronto Urban Forestry enforcement / bylaw officers if you suspect someone is doing this. They can be reached at 311.
Try green roofs or creeping vines on structures like fences, walls and other areas. Vines can offer significant cooling as long as they are properly maintained, without causing any damage.
Avoid damaging street trees. Don’t lock your bike to them, store heavy materials near their trunk or pull off bark / injure them. Try not to hit them with a lawnmower or string trimmer if you are caring for your boulevard, as this can serious damage the trees over time.
Street trees play a critical role in urban greening and urban forest health. Mitigating urban tree canopy decline involves taking care of trees throughout the city, not just on our own properties.
Become aware of heat illness, heat exhaustion and the steps you can take to protect yourself from heat exposure.
Conclusion: Urban Tree Canopy Decline
Loss of urban trees and canopy coverage the City of Toronto is a big issue for all residents. Trees provide so much environmental benefit, help to mitigate climate warming and keep our cities cool and healthy. For individuals, they play a big role in physical and mental health by cleaning the air, reducing stress and keeping us cooler as the temperature rises.
Toronto has more than 10.2 million trees, but keeping them around is not easy. Construction, the natural life cycle of trees, poor growing conditions, and other factors are putting the urban canopy at risk.” Home and business owners play a much bigger role than they realize, impacting millions of trees around the city.
The first step is taking care of your trees and keeping them healthy. The second step is participating in tree planting at home or as a volunteer in local projects.
Professional arborists, homeowners and municipalities all play a big role in making our city climate-resistant through urban forestry.
References
Beating the heat. (n.d.). Landscape Ontario Horticultural Trades Association – Landscape Ontario. https://horttrades.com/beating-the-heat
City of Toronto. (2018). Tree Canopy Study. https://www.toronto.ca/legdocs/mmis/2020/ie/bgrd/backgroundfile-141367.pdf
Climate Change Canada. (n.d.). Urban heat island effect. Climate Change in Canada | Climate Atlas of Canada. https://climateatlas.ca/urban-heat-island-effect
Climate change heat mitigation guide for homeowners. (n.d.). Climate Risk Report for Homes and Real Estate – Fire, Flood, Storm, Heat / ClimateCheck. https://climatecheck.com/risks/heat/mitigation-guide-for-homeowners
Earth911. (2023, July 11). How to combat the urban heat island effect at home. https://earth911.com/home-garden/how-to-combat-urban-heat-island-effect/
Harvard School of Public Health. (2021, September 16). The health benefits of trees. News. https://www.hsph.harvard.edu/news/hsph-in-the-news/the-health-benefits-of-trees/
News release: Extreme heat study reveals the power of green spaces in mitigating the effects of climate change. (n.d.). Greenbelt Foundation. https://www.greenbelt.ca/extreme_heat_study
Opinion: The heat island effect is so much worse than we realize. (2023, October 10). The Varsity. https://thevarsity.ca/2023/10/01/opinion-the-heat-island-effect-is-so-much-worse-than-we-realize/
Procedia Engineering. (n.d.). The Urban Heat Island Effect in the City of Toronto. Just a moment…https://www.sciencedirect.com/science/article/pii/S1877705815020676. https://www.sciencedirect.com/science/article/pii/S1877705815020676
Public Health Agency of Canada. (2023, June 1). Social determinants of health and health inequalities – Canada.ca. Health Canada. https://www.canada.ca/en/public-health/services/health-
