IT took hundreds of thousands of years, from the origin of the species until 1800, for the world's population to reach 1 billion people. It took only 130 years, to 1930, to double that number and reach 2 billion. Now the total has grown to 5.7 billion, and another billion are being added every 12 years.
This rate of growth cannot be sustained. The pressure of people on resources is already reducing living standards in much of the world and is causing environmental degradation that will lead to further declines.
So what do we do about it?
To look for some answers, the United Nations is holding another of its periodic world population conferences in Cairo …