My view is that whether the world is CURRENTLY over-populated is a bit of a red herring. Suppose it's NOT over-populated. Well, then, how many more people can we fit in it? Let's suppose we can fit in another 20 billion, before we all start choking to death from pollution, and finding difficulties producing enough food to eat reasonably well, and all the other resource constraints that would start to bite at some point. Maybe it's not 20 billion. Maybe its 30 billion. But at some point, the world WOULD be overpopulated. At that point, we would have to start asking "is it worth allowing the population to grow, knowing that it lowers the quality of life of everybody on the planet?" Should it be the 27th billion person? the 27,000,000,001th person? It doesn't really matter. The point is that at some point we would have to start limiting the population, for everyone's benefit.For a start, two-thirds of the planet is covered by the oceans, so that's out. People (and most animals) gravitate to an environment where it's possible to make a living, that's why the cities are bursting. The 'wilderness' as you call it is empty because people can't survive there - deserts, the arctic and the antarctic aren't places where you can easily grow crops and build a sustainable infrastucture.
Let's chop down all the trees in the rain forests so we can grow crops there, that's a good idea isn't it?
If that is the case, then wouldn't it be sensible to limit the population at a point where we are still NOT over-populated? Wouldn't it be sensible to say "OK, we've got 7 billion now (or however many it is) and productivity considerations don't point to the need for more people, so why allow the population to balloon any further?" Those not yet born presumably don't care (unless you subscribe to the Hubbardian theory that there are all these newly-Cleared BTs waiting for bodies), but an increasing population doesn't appear to offer any benefits to the existing population, or their heirs and descendants (aside from the very temporary issue of having enough workers to feed the burgeoning elderly population, but that problem might be better solved by figuring out how to make the large numbers of totally unproductive EXISTING people a bit more able to produce). That latter point also points to limiting the population (more exactly, the population of people who are born into situations where they are unlikely to ever be productive). How productive is an alcoholic with tattoos all over his face likely to be? Just getting his foot in the door for a job would present the first problem to surmount.
It seems to me that, with the technological advances we have made a given, a world of 1 billion people, each with a couple of acres of land to grow vegetables or do whatever they like (or whatever number makes that possible) would be a nicer world to live in than a world with cities crammed to the hilt, and everyone living in high-rise apartments. Or at least, the possibility of choosing which of those situations you want to live in.
In order to justify increasing the population, one would have to have a reason why that is an improvement. Does God measure mankind's future reward in terms of bodies-in-the-shop? Is there a surfeit of bodyless beings waiting in abject misery for a body? If not, then by what metric does one justify increasing the population endlessly?
Sorry, bit of a rambling post....