comment: >
  
  Is housing affordable in either of those cities? Aren't they some of the examples we often point to of cities that are more expensive to live in than Toronto, with even more of an affordable housing issue than we have?
  20 years ago people might have been leaving the city to single family homes, but if you drive around the Greenbelt and look at modern housing developments in small towns, the majority of them are semi-detached or townhouse "villages" on undeveloped land close to those communities, and the bigger places are building low and mid-rise housing in their cores. 
  People are leaving Toronto because they can't afford to live here, to move into (arguments to be made about how well executed they are) denser forms of housing than single family homes or single family homes on smaller lots than traditionally available in those communities, because "more house for the same money, or more house for less money" is one of the driving factors pushing people towards purchasing in the Greenbelt. 
  If you have to leave all of your friends and family and social connections and the places you used to go in order to afford a home, I understand why you would want the house to be more desirable to make that trade off hurt a little less.
  I'm not convinced London or New York are good examples of cities that have affordable housing because of their density, I think they're great examples of cities that are even more expensive that Toronto and while increasing density might help accommodate the growing population, it will also continue to drive people away as they look for more affordable housing close enough that they can still visit, and that puts them in the Greenbelt.
context: Well, the alternative is buying existing housing and tearing it down to replace it with higher capacity housing. This form of "build up, not out" doesn't require the use of more land. >
  
  There used to be surface parking lots all over Toronto, and a ton of those are now giant apartment/condo buildings. I absolutely agree that was a "better use of land" but it also drives up the cost of living as the city grows. 
  There are small-medium sized town examples where maybe it's a townhouse development or low-mid rise that goes in where there previously was a factory or mall, and where single family homes used to be there are zoning changes happening. A lot of that is adding people to existing land used for housing in ways that I can get behind, and I agree that form of "build up, not out" does seem like a great housing solution.
  Until you see the giant big-box stores that buy huge chunks of the land outside of the town you just "saved from houses" to service the significantly expanded population in that town because the increased density downtown made large property with big parking lots more expensive, because most towns with 1000 - 20 000 people can't afford to put in underground parking or vertical garages, but they can build a bunch more surface lots outside of town. 
  If towns and cities in the Greenbelt are going to continue to grow because affordability is driving people away from the GTA/other urban centres, they are going to have to build housing, roads, schools, hospitals, nursing homes, grocery stores, and the things people need in their environment to live there. I don't see how they can build all of that "up not out" without impacting the surrounding environment, AKA the Greenbelt.