Stop me if you've heard this one. There are a bunch of bacteria in a bottle and they double in number every minute. The bacteria are really small of course, but the bottle is expected to fill up after just 24 hours of growth. So one bacteria says to the other, "ahh, there's so much room in this bottle. Why, I look around me and I see that there is so much free and open space! Why, for every manbacteria womanbacteria and childbacteria in our bottle, there is enough land for ten!" and the other bacteria says "yes, that's true. What a wonderful place to live. Oh, I'm late for work, what time is it?" and the first bacteria says, "it's 11:56 pm.. four minutes before midnight".
Now, it should be mentioned, each bacteria only lives for one minute. After their minute is up, they shuffle off their mortal coil.
Three minutes and thirty seconds later, the current crop of bacteria are having a meeting. They look around. The bottle is about 75% full. However all the bacteria have started to become nervous because they can see and recognize they are running out of space. A giant effort is launched and the bacteria send out scout ships in the lab and luckily find an entire whole new bottle to populate. Celebrations are made, parties are thrown, and the new bottle is annexed in the name of bacteria-dom. All is good.
Then strangely, in the same generation, the bacteria which were teenagers during the first crisis, now old, see the same crisis repeating only this time it is approaching twice as quickly, and they are at a loss for a solution. It becomes apparent to them that their children will no longer be able to reproduce or the bottles will break and everyone will die. In a panic, having babies is made a crime.
Over the next several minutes, 90% of the population in both bottles dies. Many call the problem resolved, and the ban on babies is removed. But just a few generations later, the grandchildren of all children at the time of the ban being lifted find themselves facing the same problem. This time no one is able to react and there comes a food shortage; and as food is only added to the bottle each minute 99.99% of all the bacteria starve to death. Only a very small fraction is left in the bottle to start civilization anew.
Stop me if you've heard this before. The world population growth rate is just over 1%. Which means that it doubles in the span of one human lifetime. It's been stated that the upper limit on sustainable human population is between 10 and 12 billion. In fact, "According to UN's 2010 revision to its population projections, world population will peak at 10.1bn in 2100 compared to 7bn in 2011." (-wikipedia 'population growth').
So here we are at 7.5 billion people. The bottle is 75% full. But in stark contrast to the bacteria of the bottle most people I talk to have absolutely no idea of the need to find an entirely new planet to inhabit within our generation just so that our children can gnash their teeth at the hell they will have to go through of being forbidden to reproduce. It's either that or we need to put a worldwide ban on population growth now. Failing to do so will cause it to happen naturally (or worse, break the bottle).
I wonder what the UN is planning. A population growth rate of 1% implies a population of 17 or 18 billion in 2100 -- not 10 billion. Their figures do not make sense. The crisis will not come in 2100. It will come in our lifetimes.
we'll not keep that 1%
You'll never see over 10 billion people in your life
. At first our world is not a closed environment, therefore there are no theoretical population cap. Secondly more than 50% of the population living in cities what makes those places overcrowded, but overcrowding not equal to overpopulation. Thirdly, currently we are producing food and drinking water for more than 10 billion ppl, so there are no food and water scarcity issue, the crap what you see in many places is happening only because of the unequal distribution and extensive wasting. 
. Transgenesis is great and all genetic modification sciences could have been much further along if it wasn't for big influential groups (primarily religious) in the western world that lobby to slow it down. They use bogus arguments like yours. These groups piss me off. 
