[Osem]

There is still plenty of space around for humans but a) making that space available for habitation, agriculture etc. involves an environmental cost and b) if it is done, it simply promotes further population growth which then adds to the original problem. There's a vast amount of space in places like Australia, Canada and Russia which could in theory be habitable but would in practice be highly susceptible to further adverse climatic changes which could quickly render it uninhabitable. We're already suffering the problem here where land designated as flood plains has been built on - all very well until the rain starts falling and the rivers overflowing. Even where such land is left as agricultural we face the problem of much needed food supplies being destroyed. How much more serious would that prospect be if our population was significantly greater and our resources overstretched.

So far as I can see, the argument isn't about whether the planet could become terminally overpopulated, it's just a question of at what point that happens. The only conceivable 'solution' I can see is controlling population but how's that ever going to be achieved in practice?