As Canadian cities have sprawled, with Ottawa-Gatineau leading the way, density has dropped 6% over the last two decades, driving up tailpipe emissions from residents who rely on cars for transportation, a new study finds.
“We cannot buy ourselves more time by purchasing hybrid and electric vehicles,” Sasha Tsenkova, a professor of architecture, planning and landscape at the University of Calgary, told CBC/Radio-Canada.
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“The problem needs to be addressed at the source. We need to revitalize our downtowns and mature suburbs to keep families there. We need to bring urbanists, construction entrepreneurs, transit planners, and environmentalists together to begin to do the right things.”
Researchers used satellite imagery and census data to show how Canada’s top nine census metropolitan areas (CMAs) have developed over the past 20 years, and how that development has influenced driving habits. They focused on commuting patterns to understand how urban sprawl drives climate change.
“Urban sprawl contributes enormously to greenhouse gas emissions,” said Tsenkova. “It has an economic, environmental, and social cost.” Intensifying existing neighbourhoods and making them more walkable should be a priority over building new neighbourhoods, say experts.
The study finds that the urbanized areas for most of the CMA cities expanded an average of 34% in the past two decades, and the growth of urban areas exceeded the growth of the population to reduce overall density by about 6%. Ottawa-Gatineau showed the greatest overall drop in population, while Edmonton, Calgary, and Toronto bucked the trend to increase density.
Residents in low-density areas are more likely to rely on personal transport to travel to work or for amenities than people in high-density areas who can rely on public transit. In low-density areas, 80% use their cars to go to work—“that’s 25% more than residents of medium-density neighbourhoods (64%) and 122% more than high-density neighbourhoods (36%),” they write.
The analysis also shows that 89% of newly-developed areas are low-density, compared to just 73% of historically urbanized areas, and overall population density remains lower in newer areas than older ones. According to the research, maintaining the development trends of historically urbanized areas throughout the past 20 years would have saved 308 square kilometres from development and would have kept 129,092 cars off the roads.
In addition to cultural preferences, the trend for higher-density development is largely caused by policies that create incentives for home ownership and keep the cost of car travel low for commuters. Policy interventions—such as strong regulatory control of the housing system or fuel taxes to deter car commuting—could help steer urban areas towards more sustainable development, and steps to make these changes are critical for reducing long-term consequences.
“Urban development is a really long-term process,” said David Wachsmuth, an associate professor at McGill University and Canada Research Chair in Urban Governance.. “Most of the time, when we build something, it stays where it is for decades or centuries. That’s true for individual buildings, but more importantly true for the skeleton of urban regions. And what that means is that the decisions we make now, our grandchildren will live with the consequences.”