The only long term option is to increase productivity with education and technology because you can't increase population (however you do it) forever. We should also stop emphasising the total GDP (which can be and is boosted by adding more people) and focus on the GDP per capita instead (which seems to be falling in Canada according to the various graphs posted here).
The claim that immigration is the only option is a fallacy peddled because it's the lazy short term option and "Après moi, le déluge" [1]
Yeah, I should have mentioned productivity growth - it is of course another solution to the problem. I think it’s harder for governments to implement policy that increases productivity growth than immigration, though.
The claim that immigration is the only option is a fallacy peddled because it's the lazy short term option and "Après moi, le déluge" [1]
[1] https://en.wikipedia.org/wiki/Apr%C3%A8s_moi,_le_d%C3%A9luge