United Nations: The world population could rise by about three billion in the next 300 years to reach the 9-billion mark from around 6.3 billion at present but a slight variation in the fertility rate could plunge it to 2.3 billion or boost it to 36.4 billion, a UN report has said.

The report assumes fall in fertility rate but if that does not happen and the reproduction continues at current rate, the Earth might have to support 244 billion people by 2150 and a staggering 134 trillion by 2300, the report prepared by the United Nations Population Division has said.

In the last scenario, 134 trillion people - population density of 10 people per square foot of land - would far exceed many times over today's most crowded nations.

The report assumes two children per family while projecting that the population would stabilize at 9 billion by 2300. But it also warns that an average of one-quarter of a child more or less per family could bring it down to 2.3 billion or raise it to 36.4 billion by 2300.

PTI