So, I went to Stats Cans site see what they think 'realistic' scenarios of growth look like.
https://www150.statcan.gc.ca/n1/pub/...estdm1-eng.htm
Based on this publication, by 2061, which most here would hope to be within their lifetimes, they peg 52M-64M as a reasonable guess.
If you take the high forecast and apply that growth rate to the end of the century, you get something in the ballpark of 100M.
So I think that's a logical place to start in terms of imagining where Canada may head, mixing a tad of fantasy, with a bit of reality.
Rather than throwing darts at a map, my first thought as to where growth would occur, is how much fresh water is easily accessible.
That makes Cities on the Great Lakes and St. Lawrence obvious choices for growth.
I'd be much more concerned about cities that are dependent on glacier-fed rivers in a era of climate change. (Calgary)
Beyond the obvious then, where do we have vast fresh water, but few people?
Lake Winnipeg immediately comes to mind, Reindeer Lake, Lake Athabaska, Great Slave Lake, and Great Bear Lake, round out the 'Big 10' (excluding the Great Lakes).
Of these the best prospect for growth in the near term would be Lake Winnipeg, that areas of Manitoba does not currently house even one material population centre. So
I'm not sure where it would make most sense to grow a new city. Presumably on the #6 corridor, maybe something about 1/2 way to Thompson.
Looking at lesser sized lakes that seem underdeveloped and near existing urban settlement or transportation leads me to think that the Lac-Saint-Jean area of Quebec would make sense of an urban centre of size.
North Bay Ontario has abundant water, a university and is connected to transporation.
Trois Rivieres would make sense.
Hay River would be a good choice for growth as well, on a huge body of water, connected to rail already.
For existing cities, for a major move upwards in population, Thunder Bay, the Sault, Windsor all make sense. So would Owen Sound in Ontario, and Barrie.
Kingston in Ontario makes sense, and it would be logical to have one other city of size on Lake Erie. Pt. Colborne or Pt. Stanley would make the most sense, taking advantage of the nearby size of Welland and St. Thomas respectively.
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I'm not as familiar w/the natural limits of growth in Mtrl or Vancouver.
But in the GTA, I think the City proper can top out at round 4.5m by 2100, anchoring a region about 4 times that size, or around 18M