Everyone needs to realize that over-population will be the greatest disaster on this planet. Here is a plan that could achieve zero population growth.
With the current global financial crisis, there has been much talk about the dot.com bubble, the housing bubble, and the stock market bubble. Unfortunately, we have another already huge and growing bubble that is being ignored... the global population bubble. Currently, there are 6.5 billion people, and that is projected to increase to 9 billion by 2050. Already, humans are causing widespread global devastation, which will only increase as the population increases. Genocide, famine, and wars will only increase as the population increases and resources become more scare.
I propose a fix to the population bubble: when a man or woman reaches adulthood, each would get a certificate for one child. This is a fair method for halting global population growth. If a family wanted to have more than two children, they would need to obtain (buy or receive) additional certificates. If individuals didn't have children, they could sell or give away their certificate. Unwanted pregnancies could be aborted or could be delivered for adoption to another person who had a certificate. Governments would safeguard the certificates.
The religious would oppose this solution saying, "It is God who must decide this." My reply is, "If it is God's will for families to have more than two children, then pray and He will get you another certificate." No octomoms or procreating like other animals.
If you agree that we are ignoring the population bubble and need to implement some kind of zero population growth, then please publish this solution at other sites. Just like Global Warming is a looming disaster, unregulated human population growth will likely lead to the worst disasters on this planet.