The world is not over crowded, but merely under developed.
For instance, there are growing myths about population that it lowers per capital economic growth! That is nonsense, only take a look at the UN data population and human development report from 2007 to see the amount of countries improving with population growth. Remember people are a resource too.
The supply of natural resources are finite. Again Nonsense, Man always finds new resources. The romans used wood for heating and building, then we went onto coal,recently oil and gas and when they run out man being ingenuis as he is will find something else or use existing power, wind, sun e.c.t and develop that for energy.
Countries are too cramped with people. Nonsense, foe example Hong Kong has a population densitie of 5,871 person per sq.km. But Canada has a population densitie of 3 per sq.km. China 128 persons per sq.km, Africa 48 persons per sq.km and the UK 241 persons per sq.km. I stay in scotland and the land mass is the same as England yet we have 5 million persons here while they have closer to 60 milion. Plenty of land left.
If the world went vegetarian you could feed 80 billion people no problem every year. Which I would hate, how could anyone give up a bacon roll, I don't know?
Any calculations of any future population celing must depend on simple speculation about - the future state of technology and the future state of the world economy.
~This has been a long running argument between the neo-Malthusians or Ecological pessimists vs The economic optimists.
I have written a number of essays on the subject and my conclusions are that under current capitalism the gap between poor and rich nations has never been greater, For instance Nigeria is a oil rich country, but infant mortality has went slightly up and standard of living not moved up. Due to corruption it does not invest into their soco-economic infrastructure and with the world bank and IMF demanding money back from Countries in Africa when they experiance drought and famine it will only get worse. But with any doubt man has the answers to sort this out, but whether he has the desire is entirley another question.
Excito