This topic has always interested me. A few points I'd like to make...
Firstly, the growth will slow itself. The massive rise in population over the past century didn't come from higher fertility rates (in fact, fertility rates have been declining over past half-century globally, even in most of the third world), it came from longer lifespans and lower mortality (same number of kids, but they were all far more likely to survive infancy/childhood and do so for longer). Unless our lifespans double and our mortality rates are cut in half again any time soon(unlikely), the growth will top out sometime in the middle of this century-it can't continue into perpetuity as some fear, and even if it did, something would have to give(read: If earth really can't support 15 Billion people, then we won't see that many humans).
Secondly, we often overlook another problem when we talk about population pressures. Most developed nations today actually need more people, not less. Contrary to popular belief, population decline is not superior to population increase-both are destructive to society. The last thing most developed (particularly European) nations need right now is more birth control-they need fertility, preferably up to about replacement level(2.1-2.2).
Thirdly, don't be so sure the earth cannot support 7-10 Billion people. The famines and other concerns we face are not all due to a mere lack of capacity-human fault (corruption, mismanagement, etc) as well as the varying proliferation of technology (read: farmers in USA get much higher yields out of one acre of land than their third world peers) plays a big role as well, and these things are correctable.
Finally, politics: there is no practical solution to stop the growth. None of the solutions commonly proposed by some in the West (mandatory vasectomies, one-child policies, etc) are politically feasible, and most importantly, even if they become feasible, the developing world will ignore them entirely. This would just result in a demographic reshuffling(fewer westerners, more everyone-else), not a decline.
As it is, the vast majority of this growth will take place in the developing world. Actually, I'd venture to say that nearly all of it will.
Here is the
list of countries by fertility rates, from highest to lowest.
Focus on the top 50. Six of the listed nations/territories are from the Arab World (Western Sahara, Gaza Strip, Jordan, Iraq, Yemen, Afghanistan), one is in Latin America(Guatemala) and four are in the South Pacific/Micronesia(Tonga, Marshall islands, Papua New Guinea, Solomon Islands).
The first Western/developed nation on the list is Israel at number 75. After that it is New Zealand at 119(Polynesians are a significant factor there), then the USA at 122.
The complexion of the world is about to change quite a bit. As it does, you can expect natons facing rock-bottom fertility, population-aging and population decline to start competing for immigrants(preferably the more educated ones at first) from these developing nations. They'll soon have no choice. A lot of countries are going to look very different in the coming decades as new arrivals begin to pour in out of necessity. Of course, this will not be a seamless transition, at least not in all cases.
It is going to be an interesting 50 years to come.
