One aspect of the future that didn't show up very much in science fiction, but which is lurching toward reality at an increasingly rapid pace, is the concept of vertical farming - that is, agriculture conducted not on a traditional farm, but within a purpose-built skyscraper. The true effectiveness of large-scale vertical farming is still up in the air, owing to the newness of the concept, but if it lives up to the possibilities it may well revolutionize patterns of development in the twenty-first century. If we're looking to build a resilent society, bringing food production into the city is a necessity - municipalities today do not maintain strategic food reserves.
What I've been thinking about recently are some of the other potential consequences of a shift in agriculture from traditional rural to controlled urban methods, particularly in terms of land use. It can be argued that, in addition to their agricultural role, farms also end up serving as "land banks" - just as banks will give you interest on your savings account in exchange for letting them work with your money in the meantime, farms reap rewards out of the soil until some developer comes along, buys out the farmers, and slaps down a soulless cookie-cutter subdivision with streets all named after the sort of things that used to grow there. This happens again and again in Ontario - just recently, a pioneering project to stem the town of Markham's sprawl into adjacent farmlands was rejected, thanks in part to the ceaseless pressure of developers who, it seems, won't be happy until every patch of green is plowed under.
A large-scale shift to vertical farming, should it live up to expectations, could upset this balance in many ways. Farming is, to be blunt, not the sort of profession that makes a person rich. If agriculture starts moving away from farmers' fields into controlled environments, it might not take long to reach a tipping point where farms become valuable only for the land they're sitting on - perhaps sparking a land rush among developers jockeying for the best territory on which to put their empty suburbs. That, in turn, could bury any shot at suburban densification.
It wouldn't necessarily have to be that way, though. Ontario already has a provincially-protected Greenbelt and has made an attempt at conserving the environmentally-sensitive Oak Ridges Moraine, although admittedly the enforcement of that protection has been spotty at best considering 200,000 people already live within it. A sufficiently forward-looking government could buy up the land ahead of the developers, perhaps to set up a network of provincial parks and secure the land against the relentless pace of development. There's no reason other governments in other jurisdictions couldn't do similar things.
The plowing-under of nature is, regrettably, one of the things that did frequently appear in science fiction, and which has long since become science fact. If urban agriculture does lead to the contraction of rural farmland, if we move fast enough we may yet stand in the bulldozers' way.