The world is heading for wildly uneven population swings in the next 45 years, with many rich countries "downsizing" during a period in which almost all developing nations will grow at breakneck speed, according to a comprehensive report by leading US demographers released yesterday. They predict that at least an extra 1,000 million will be living in the world's poorest African countries by 2050. There will be an extra 120 million Americans, and India will leapfrog China to become the world's most populous country. One in six people in western Europe will be over the age of 65 by 2050.
But the populations of some countries will shrink. Based on a number of factors, including analysis of birth and death rates, Bulgaria is expected to lose almost 40% of its population.
Britain is expected to grow faster than any other major European country. Within 20 years, the authors expect it to have four million more people, at which point its growth is expected to tail off, adding only a further 1.5 million in the next 25 years to eventually reach 65 million. By then it will have overtaken France as Europe's second or third largest country, depending whether Russia is classed to be in Europe or partly in Asia.
The changes, considered inevitable given present trends, will transform geo-politics and fundamentally affect the world's economies, people's lifestyles and global resources, suggest demographers with the Washington-based Population Reference Bureau.
Countries such as Nigeria and Japan, which today have similar sized populations of about 130 million people, could be unrecognisable by 2050, say the authors. By then, Nigeria is expected to have more than doubled its numbers to more than 300 million people. But Japan, which has only 14% of its current population under 15, may have shrunk to roughly 100 million people.
Among the major industrialised nations, only the US will experience what the authors call "significant" growth. It is expected to have reached a population of 420 million by 2050, an increase of 43%. But Europe is expected to have 60 million fewer people than today and some countries could lose more than a third of their populations.
Eastern Europe is leading the world's downshifters. Bulgaria is expected to return to pre-1914 population levels, losing 38% of its people, while Romania could have 27% fewer and Russia 25 million (17%) fewer people. Germany and Italy are expected to shrink by about 10%.
The projections are based on detailed analysis of infant mortality rates, age structure, population growth, life expectancy, incomes, and fertility rates. They also take into account the numbers of women using contraception and Aids/HIV rates, but do not allow for environmental factors.
Climate change and ongoing land degradation are widely expected to encourage further widespread movements of people and increase pressure for migration away from rural areas towards cities and richer countries.
The population changes are causing growing alarm among experts, who believe sustained growth in developing countries can only be managed with economic help from rich countries. "World population is going to grow massively in some of the most vulnerable countries in the world. We have to ask how rich countries are going to help," said Kirstyen Sherk, of the Planned Parenthood Federation of America.
The former World Bank economist Herman Daly believes globalisation and the uncontrolled migration of cheap labour could put potentially catastrophic pressures on local communities and national economies. "The sheer number of people on Earth is now much larger than ever before. Some experts question whether Earth can even carry today's population at a 'moderately comfortable' standard for the long term, let alone 3 billion more."
The report, based on countries' own statistics, confirms trends identified earlier by the UN, and more recently by the US Population census report. While the world's few developed countries are expected to grow about 4% to over 1.2 billion, population in developing countries could surge by 55% to more than 8 billion.
Africa and Asia will inevitably be transformed. Western Asian nations are expected to gain about 186 million people by 2050 and sub-Saharan African countries more than one billion people. By 2050, India will be the largest country in the world, having long passed China.
How some countries will cope with the changes is debatable. Bangladesh, one of the poorest, most crowded and disaster-prone countries, may have doubled numbers to more than 280 million.
Overall, says the report, world population is growing by about 70 million people a year, and will likely reach 9.3 billion by mid-century from 6.3 billion today.
However, a separate report, to be published soon by the Washington-based Worldwatch Institute, will argue that fertility rates in poor countries could drop if there is a world fuel crisis. The thinktank says people usually have as many children as they think they can afford, and the motivation to have fewer comes from anticipating hard times ahead.
Increases in food production per hectare, it will say, have not kept pace with increases in population, and the planet has virtually no more arable land or fresh water to spare. As a result, per-capita cropland has shrunk by more than half since 1960, and per capita production of grains, the basic food, has been falling worldwide for 20 years.