You're conflating two seperate issues. We were on about Africa and other third world regions with high birth rates.
Here in the UK, we have had a low birth rate and high life expectancy for decades.
The third world (and developing world) generally have a lot of catching up to do with regard birth rates, and life expectancy, and we have no moral reason not to allow them to acheive that. Infact there is much to gain to allow them to develop, and gain the benefits of an industrialised world. There are risks as well of course, but if we make every effort to clean up our act, the lessons can be learned elsewhere.
For example, China may be using obscene amounts of coal, but they are also building more renewables than anyone else. They and us need to be building more nuclear power plants. And never forget that it is us that is feeding that industry (the West), with us buying their goods en masse.
http://www.bbc.co.uk/news/magazine-21432226
The biggest container ships will be saling from Asia to Europe.
We need to develop clean technology. Not just for us to use, but for the world. Its a global market, and a global issue of emissions.