Why Park Ex gets so hot?

What can be done to mitigate the effects of heatwaves

Photo1: People in areas like Park Extension are especially susceptible to the negative effects of heat waves. Photo: Jarosław Kwoczała via Unsplash

With summer in full swing, many Montrealers are making the most of the sunny weather and warm days. But the same can not be said for those particularly vulnerable to higher temperatures brought on by climate change and longer-lasting heatwaves.

This was made especially clear with the recent heatwave in Western Canada, that brought on the highest temperatures ever recorded in Canada and a series of subsequent destructive wildfires.

But urban areas are not immune to problems caused by rising global temperatures either. Those with underlying health issues and elderly people are especially at risk of severe health complications or even death during high temperatures.

People in areas like Park Extension are especially susceptible to the negative effects of heatwaves due to the environment they live in and certain socio-economic conditions. 

What is an urban heat island?

An urban heat island is a phenomenon in which urban areas will experience higher temperatures than surrounding rural areas due to the built environments’ capacity to absorb, retain and release heat.

Urban areas like Park Extension, are made up mainly of concrete, asphalt and brick and tend to absorb sunlight in the day and release it as heat in the evening and overnight.

“Built surfaces will absorb solar radiation and later release it as long-wave radiation,” said Dr. Raja Sengupta, an associate professor at the McGill School of Environment and Geography Department who researches and lectures on the matter. 

“It’s actually at night that it is hotter in urban areas,” he added.

Heat islands are further compounded by lower tree and plant coverage, which would otherwise help to create shade and cool an area through vegetation’s naturally occurring transpiration. 

Areas in red show city data on a higher propensity for a heat island effect. Park Ex is disproportionately affected by higher heat when compared to the neighbouring Town of Mount Royal. Data: Ville de Montréal

Vulnerable populations

The effect is especially felt in Park Extension. One only has to walk across de l’Acadie Boul. to the neighbouring Town of Mount Royal to feel the temperature difference.

According to research conducted by Jia Yi Fan, supervised by Dr. Sengupta, low-income individuals in Montreal are more vulnerable to the effects of urban heat islands. With many living in smaller apartments without proper climate control, they are at higher risk of climate injustice due to their socio-economic position and where they live.

“It’s not the heat that is the problem, but the access to air conditioning,” said Dr. Sengupta, adding that many can’t afford them. The problem is further exacerbated by the area’s lack of outdoor green space, oftentimes the only reprieve from the heat of indoor spaces. 

“The positive externalities of greenspace push lower-income people out,” said Dr. Sengupta on why poorer areas often don’t have as much access to greenspace. That socio-economic divide also becomes clear when comparing the Town of Mount Royal to Park Extension.

Double the effort needed

The question was also brought up by a citizen during the July borough council meeting. The borough is currently developing a greening plan that would try to address the issue.

“We have to double our efforts to increase canopy cover,” said borough Mayor Giuliana Fumagalli, adding that she hoped to adopt a new greening master plan by the fall of 2021.

“This is why we put in a rule that prevents a building owner from removing grass and installing paving stones,” further added city councillor Mary Deros on rules that prevent property owners from removing greenspace. 

Fumagalli also underlined the work the borough had done so far, including laneway greening efforts, the planting of over 4,500 new trees and the removal of 2,000 square meters of asphalt along roads to make way for more vegetation.

A need to build differently 

Although the negative effects of urban heat islands cannot be fully eradicated, much can still be done at a local and individual level to mitigate them. 

“It’s better to replace impermeable surfaces with permeable surfaces,” recommended Dr. Sengupta, suggesting that concrete and asphalt surfaces be replaced with grass and vegetation. Experts also recommend the planting of more trees to provide shade and to naturally cool down areas.

A study conducted at the University of Wisconsin in 2019, found that American cities needed 40% more tree coverage to meaningfully mitigate urban heat islands. Greening can therefore be achieved through individual and governmental initiatives, from planting a flower bed to building a new park.

Other tactics are also being developed elsewhere. According to a recent article in The Economist, building codes should be updated to help address the temperature effects of building materials. Painting dark surfaces like roofs and streets white would better reflect solar radiation.

With global temperatures set to continue to rise even in the event carbon emissions are reduced, it is up to people and their governments to better adapt to impending changes. 

The sensors used in Dr. Raja Sengupta’s research to measure temperature differences across urban areas. Photo: Raja Sengupta.