LAWRENCE MCGINTY:

Zachariah Kahn (ph) came into the world at the Rosie Hospital in Cambridge. Around the world, three other babies were born in the same second.

First, the figures. It took all of human history up to 1804 for the world's population to reach 1 billion. But the next billion came only 100 years later, in 1927. And after that, the rate of growth accelerated, 3 billion in 1959, 4 billion 1974, 5 billion 1987, 6 billion 1999, and now 7 billion. We're adding a billion population every 12 years.

Population growth will not be even around the world. In Africa, for example, the current population of 1 billion will increase to 3.6 billion by the end of the century. But, in Asia, yes, population will increase from its current 4.2 billion to 5.2 billion by 2050, but by the end of the century, it will fall to 4.6 billion.

SIR JOHN BEDDINGTON, government scientific adviser: If you go just two decades ahead, all the trends are indicating that we are going to need to be producing something like 40 percent more food, 40 percent more available freshwater, and actually about 50 percent more energy. And, remember, that's clean energy.