Joni Mitchell was right – they are surely paving paradise and putting up parking lots.
Statistics Canada‘s first survey of urban green space shows that, just because the singer-songwriter warned, cities across the country are getting greyer and browner.
“We did a see a decrease over the time period we checked out,” said Jennie Wang, who helped prepare an enormous report from the federal agency released this month on human activity and the environment.
StatCan used satellite imagery to estimate the quantity of green space in Canadian cities – parks, urban trees, even backyards and lawns. The info has existed for years, however it was used for this purpose.
“(We’re) getting a way of the condition of vegetation in urban areas,” Wang said. “It’s the primary time we’ve done that.”
The researchers checked out 31 urban centres of varied sizes across the country. They compared satellite images from 2001, 2011 and 2019.
They found about three-quarters of huge and medium-sized cities were less green in 2019 than that they had been 20 years earlier.
“You find yourself seeing less green as you walk down the road,” Wang said.
Big losers include cities equivalent to Kelowna, B.C., which went from nearly three-quarters green to lower than half. Milton, Ont., went through an analogous drop, as did Winnipeg.
Toronto, Montreal, Vancouver, Calgary and Edmonton all lost green space. Saskatoon and Regina were among the many few that gained.
Urbanization is a giant driver of green space loss, said Wang. Milton grew by 350 per cent over the course of the study and Kelowna’s population grew from 150,000 to 223,000.
Other aspects equivalent to drought or insect infestations also play a task. Winnipeg’s losses, for instance, were exaggerated by the emerald ash borer.
However the losses are real, said Wang, and have real implications.
“There’s been studies showing the numerous advantages of vegetation,” Wang said. “There’s reductions in energy use, trees remove air pollutants. ”There’s also research looking into human health advantages.“
Green spaces also reduce what’s called urban heat islands – bubbles of extreme temperature around cities.
Sandeep Agrawal, a geographer and concrete planner on the University of Alberta, has found the temperature difference between a city equivalent to Edmonton and the encompassing countryside might be as high as 5 or 6 degrees. That differential is linked with the quantity of urban green.
“If the tree cover goes down, the urban heat island effect goes up quite a bit,” he said.
Heat islands can assist cause human health problems equivalent to respiratory failure or heat stroke, an issue worsened in heat waves equivalent to that experienced last summer over much of Western Canada.
The B.C. coroner’s office identified 569 heat-related deaths between June 20 and July 29.
There’s no going back once a pasture or woodlot has been bulldozed for houses or shopping malls, Agrawal said. Even when the landscaping matures, it doesn’t fully replace what was there before.
“You’ll be able to never do this,” he said. “It’s just impossible.”
Governments are starting to acknowledge the problem, he said, making it tougher to chop trees on public land and enacting laws promoting so-called “green roofs,” vegetation planted atop buildings.
Most Canadians live in cities, Wang said. She said her research can assist governments work out how their policies are affecting the trees and grass that live alongside the urban concrete and asphalt.
“This sort of information can assist cities monitor whether there’s been an effect from their policies.”
