Global population forecast falls
11:18 27 February 03 NewScientist.com news service

Fast-falling birth rates and rising AIDS deaths are stifling the population explosion - and could lead to a decline in global population in the second half of the 21st century.

In new forecasts released on Wednesday evening, UN demographers cut 400 million from their best estimate of the world's population in 2050. Joseph Chamie, the head of the UN population division in New York, said he now expected 8.9 billion people on Earth in 2050, rather than the 9.3 billion that he forecast in 2002. The current figure is 6.3 billion.

The 400-million reduction equates to the current populations of the US, Canada and Mexico combined. Chamie said half arose from birth rates falling faster than expected and the other half was due to rising forecasts of the death toll from AIDS. "HIV/AIDS is a disease of mass destruction," he said.

The new population projections stretch to the year 2050, but not beyond. However, he warned that "fertility rates will be below replacement levels in three-quarters of the world by 2050". The great majority of women worldwide will be having fewer than two children.


Radical re-think

In fact, the new projections assume that most countries will eventually approach a fertility rate of 1.85 children per woman. This represents a clear break with past thinking - demographers had always assumed countries would settle down to replacement fertility levels.

Chamie agrees that it has "momentous" implications for humanity. After a time-lag during which past "baby boom" generations pass through child-bearing age, it will cause most countries to go into a demographic decline.

The detailed projections for individual countries show 33 countries with smaller populations in 2050 than today. Japan is expected to be 14 per cent smaller; Italy 22 per cent; and a slew of eastern European countries, including Russia and Ukraine, will see their populations crash by between 30 and 50 per cent.

Inward migration

The population of South Africa and three neighbours is also expected to reduce, but as a result of the AIDS. Chamie predicts the disease will have claimed 278 million lives by mid-century.

The US is expected to be one of a handful of developed nations whose population will continue to grow strongly, largely through an inward migration of more than a million people a year.

The US population is predicted to rise from 285 million now to 409 million in 2050. The UK is also expected to have more people then, rising from 59 million to 66 million.

The next five decades are also set to see a massive ageing of the world population. The number of people over 80 will rise fivefold. The median citizen - the one with half the world older than him or her and half younger, will be aged 37 in 2050, compared to 26 today.


Fred Pearce