I, for one, don't consider this to be an actual problem. Truthfully, I think it's a good thing societally and ecologically, but I'm in the minority. Luckily, there are some folks out there (in the former East Germany) who are thinking creatively about their demographic issues and don't see it as a problem but as a chance for some creative thinking about urbanism and how we live today. Here's an excerpt of a piece I just wrote over on the Helium.com site on this topic:
What if "dying" cities began to reclaim abandoned urban spaces for localized agricultural purposes? That would not only be a smart ecological move, but it could foster a sense of pride in place and tie existing residents to the "soul" of the city. Who knows, that may encourage people to have kids to grow up and inherit this city with newfound love.There are many cities whose population bases are shrinking but can't seem to get out of the "We must grow and expand to survive!" mode of thinking. Unfortunately they can't seem to realize that their time in the sun is over and they must move on, establish a new rationale for existing. As I mention in my article, Detroit is a city that could use some new thinking like this. So much of that landscape is comprised of (nearly) contiguous abandoned buildings and empty lots that they could establish all manner of parks, urban gardens, local farm plots. Of course a lot of work and bureaucratic wrangling would have to occur, but it's not beyond the scope of actual planning. Population decrease doesn't have to be the monumental catastrophe that too many people are making it out to be, but it does require a shift in our thinking; a shift in our perceptions of where our societies should be heading and the goals we should really be focusing on.