According to their study, the development of green belts on the outskirts of metropolitan areas could help curb this polluting phenomenon. These belts are protected areas, such as forests or agricultural land, surrounding a city and even a region where real estate development is severely restricted or even banned.
According to Parnian Pourtaherian, the lead author of this report, published in the journal Landscape and Urban Planning, these spaces would prevent the often disorderly expansion of suburbs and certain economic activities.
Using open-source data, the researchers tracked the urban sprawl of 60 European cities from 2006 to 2015, half of which had green belts. These were divided into four categories: very large cities (2.5 million inhabitants and more), large cities (more than 1 million inhabitants), medium-sized cities (500,000 to 1 million inhabitants) and medium-sized cities (96,000 to 500,000 inhabitants). .
Aerial view of the Limoilou District and north of Quebec City
Photo: Radio Canada
According to this study, 90% of cities with a green belt experienced a decrease in urban sprawl in the given time period. In contrast, only 36% of the other cities experienced such a decrease.
“We found large differences in the effectiveness of green belts in small, medium and large cities, but the difference in relative changes in urban sprawl was more pronounced in larger cities. »
— A quote from Parnian Pourtaherian, lead author of the report
Parnian Pourtaherian, who has a master’s degree in natural sciences from Concordia University’s Department of Geography, Urban Planning and the Environment, argues that this method could also be used across Canada.
Ottawa and Toronto both have green belts, and Vancouver has a “green zone” that functions as such. On the other hand, Montreal doesn’t yet have a real green belt, but it urgently needs one, she says.
Effective when well regulated
For Jochen Jaeger, a professor in the Department of Geography, Urban Planning and the Environment at Concordia University, green belts are almost always effective when they are well managed. Their effectiveness can be compromised if they’re not properly protected, the researcher points out, or if they’re too small or too tight.
Some developers and politicians are using the housing crisis argument to expand large housing developments and allow additional dense urban growth or even repeal existing protection laws. They are also employing a “salami tactic” to destroy the green belt, arguing that every little bit lost is just a “pointless” loss until nothing is left, laments the study’s co-signatory.
These green belts are a major obstacle to urban sprawl, which consists of an increase in urban areas in a given area. This phenomenon is characterized by low compaction and a large area, often only accessible by road.
This suburban sprawl appears to have coincided with population growth, but its sprawl removes residents from the services offered in the major centers and threatens the fauna and flora on the outskirts of the cities.
“Limiting urban sprawl is critical as it leads to loss of green space and wildlife habitat, as well as reduced ecosystem resilience due to habitat fragmentation, declining wildlife populations and extinction of local species. »
— A quote from Jochen Jaeger, Professor at the Department of Geography, Urban Planning and the Environment at Concordia University
The researcher adds that these effects would be exacerbated by the climate crisis, which would lead to higher spending on transport infrastructure, power distribution, water supply and sanitation. Urban sprawl is also associated with increased use of fossil fuels for transportation and the loss of fertile agricultural land.
Avoiding the expansion of sparsely populated urban areas into natural spaces helps preserve the benefits of those spaces — including better air and water quality — that today’s generation can then pass on to future generations, he concludes.