UN predicts population of 9 billion by 2300

The world's population will be around nine billion by 2300, says the United Nations.

But the UN Population Division said a small shift in fertility levels could have an enormous impact on the population, now 6.3 billion.

The nine billion estimate is based on the two-child family, but as little as one-quarter of a child less or one-quarter of a child more per family would lead to world populations in 2300 ranging from 2.3 billion to 36.4 billion, it said.

Even more startling is the projection of world population in 300 years if fertility levels remain unchanged - it would jump to 134 trillion people, with virtually all the increase in the developing world.

By contrast, developed countries would decline: Russia, Italy and Spain would be only about 1 per cent of their present size if their fertility rates remained constant until 2300, he said.