Canada has recently been the fastest growing country in the G7, with a population rising at double the pace of the United States and United Kingdom, and four times that of France and Germany.

According to Statistics Canada’s projections, our country could have 48.8-million people by 2050. And that’s the agency’s “medium” growth projection; under a high-growth scenario, there could soon be 56-million Canadians.

Nearly all of these future residents are going to live in this country’s handful of big cities. That means millions of new urban dwellers – and millions of new commuters.

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If we want to raise the quality of life in Canada’s cities, rather than choking on our growth, we will need better planning, so that cities build up more and sprawl out less. As part of that, we need a lot more of the key piece of infrastructure that makes city life possible: mass transit.

There is, unfortunately, a stark contrast between the size of urban Canada’s coming population boom, and the history of delay, denial and underfunding that has marked too many attempts to build badly needed public transit. Our creaking transit systems aren’t up to the demands of the present, let alone the future.

How much bigger are our cities about to become?

‘Quality of life will go down for the average Canadian.’ How readers feel about Canada’s cities adding millions of new residents

Let’s start in British Columbia. The province’s demographers expect that B.C., with 5-million people today, will grow by 1.3-million by 2041. More than three-quarters of those new residents are expected to make their homes in the Lower Mainland, a.k.a. Greater Vancouver.

That’s an extra million people in Canada’s third largest city, in just two decades. It’s the equivalent of the entire population of Prince Edward Island moving to Vancouver, every three years. Before a child born today has graduated university, the Vancouver area will have added nearly as many people as currently live in Saskatchewan.

No, a million more people are not all going to be able to drive to work.

Or consider Alberta. Over the next quarter-century, according to the Alberta Treasury Board’s projections, the province expects to add 2.3-million people – 80 per cent of them in Edmonton, Calgary and the corridor between the two cities. That would mean urban Alberta growing by two Nova Scotias or four Newfoundlands.

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In Quebec, the Institut de la statistique projects the province will add 1.1-million people between 2016 and 2041, nearly three-quarters of them in Greater Montreal. The Montreal area already has as many people as Alberta; over two decades, it will add the population of Winnipeg.

And then there’s Toronto. Every day, it becomes more of a global megacity.

According to Ontario’s projections, the Greater Toronto Area will grow from nearly 7-million people to 10.2-million by 2046. Add the horseshoe of growing communities around the GTA, from Niagara to Kitchener-Waterloo to Barrie and, by 2046, what we’ll call the Greater, Greater Toronto Area will have 14.6-million people, up from 10 million today.

That’s an extra 4.6-million residents, more than the population of Alberta, soon to be making their homes within roughly 100 kilometres of the corner of King and Bay streets.

And that’s Ontario’s “medium" growth estimate. There’s also a high-growth scenario. Under that projection, by 2046, the GGTA might have nearly 17-million people. That’s like dropping five Manitobas into the Toronto region, or six Saskatchewans, or one-and-a-half Albertas.

Try to imagine millions of new commuters, all trying to drive to work on the GTA’s already gridlocked highways. It can’t be done.

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Canada’s growing population is, in most respects, a success story. The economy will have no trouble creating jobs for all our new citizens, and there’s a good chance the country will end up not just bigger but more dynamic. Boom times and swelling confidence accompanied earlier periods of high population growth, such as during the spike in immigration before the First World War, or the Baby Boom after the Second World War.

But all this growth comes with challenges and downsides. Unless municipalities, provinces and the federal government prepare for our nation’s future as a bigger and more urban country, by planning, funding and actually building public transit, and a lot more of it, the quality of life in Canada’s big cities is at risk.