Parks and urban greenery can help reduce the impact of extreme heat waves that are now the leading cause of weather-related illness and death in Canada, write two researchers with the Smart Prosperity Institute.
“Consider black asphalt on a hot summer day,” write research associates Talha Awan and Christine Desrochers. “It absorbs heat from the sun and radiates it back to the surroundings,” becoming “the main cause of the urban heat island effect. Pavements and buildings trap heat and increase the temperature of the entire city,” making urban landscapes up to 12℃ warmer than surrounding rural regions on particularly hot days.
With the next five years on track to be the warmest ever recorded, “millions of Canadians are at risk,” Awan and Desrochers warn. “This represents an urgent health crisis which we must take action to prevent.”
Already, they add, extreme heat is an economic burden on an overstretched health care system, driving up the rates of heat stroke, heart disease, and respiratory diseases like asthma while making pre-existing conditions worse. “Heat islands also increase air conditioning use, which raises electricity costs and peak electricity demand. Surplus demand is often met with dirty, carbon-intensive power plants, such as coal or natural gas, thus contributing to air pollution and increased GHG emissions.”
But cities hold part of the solution in their hands, with street trees, urban forests, parks, green roofs, gardens, green walls, and other green infrastructure all available to reduce the urban heat island effect. “Trees help cool the environment by providing shade. Vegetation also cools the air through evapotranspiration,” the two authors explain. “In areas that have competing demands for space, strategies such as green roofs, vertical greening, and linear parks and trails can also be implemented.”
Smart Prosperity lists an eco-roof incentive in Toronto and a demineralization and tree planting project in Laval, Quebec as examples of successful urban greening initiatives.