Seven billion people today – sixteen billion by 2100?

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By Steve Elliott our Science and Health correspondent 

This month we can wish a happy birthday to the 7 billionth baby born on Earth – the human population is currently increasing by 200,000 a day.

It took 250 thousand years to put the first 1bn humans on Earth by 1804, just over a hundred years later there were 2bn in 1927, 3bn by 1959, 4bn by 1974, 5bn by 1987, 6bn by 1999 and 12 years later 7bn today – this is basically exponential growth.

By Steve Elliott our Science and Health correspondent 

This month we can wish a happy birthday to the 7 billionth baby born on Earth – the human population is currently increasing by 200,000 a day.

It took 250 thousand years to put the first 1bn humans on Earth by 1804, just over a hundred years later there were 2bn in 1927, 3bn by 1959, 4bn by 1974, 5bn by 1987, 6bn by 1999 and 12 years later 7bn today – this is essentially exponential growth.

It’s predicted that the population will likely continue to rise over the coming decades due to 3 factors: a higher percentage of the world’s population being in their reproductive years than ever before; more children surviving to adulthood because of improved sanitation and health care, and around the world ever greater numbers of people are living longer.

Conservative UN figures predict a world population of 8bn by 2025, 9bn by 2050 and possibly 10bn by 2100 – even climbing as high as 16bn by 2100 based on one possible population growth scenario.

A large part of the population rise that will continue up to 2050 is predicted to come from sub-Saharan countries already experiencing inadequate supplies of food and water.  Ethiopia for example, could see a population rise from approximately 80mn to 145mn over the next 40 years.

The growing population of the world, especially in developing countries, means that providing sufficient space, shelter, medicine, sanitation, energy, food and water will become increasingly challenging issues as the 21st century progresses onwards – climate change will add to the difficulties.

However, the increasing populations of developing countries is not reflective of a worldwide trend because the era of population growth acceleration appears to be coming to an end.

The UN predicts a possible, even probable, scenario where the Earth’s population might actually fall to 6bn by 2100 due to a fall in human fertility – that’s 1bn fewer people on the planet than are present today.

The world population acceleration we’ve experienced around the planet continued unabated in the 1950s and 60s with the period called the baby boom in rich countries mirrored by very high birth rates in poor countries.

Today though, momentum of population growth is shifting from increasing to decreasing population growth because the total fertility rate (the number of children a woman can expect to have in her life-time) has been falling for a long time and families are getting smaller.

Worldwide in 1950, women had an average of 5 children per family, now the average is 2.5 .  A small drop in global fertility could have a much larger, more dramatic effect on the planet’s human population.  In many countries around the world – including Russia, Japan, Europe, Brazil and even China – fertility is decreasing so much that populations are reliably predicted to fall later this century.  In some countries the number of children per woman has fallen at a remarkable rate e.g. in Iran, a woman had 7 children in 1950 but today the average is less than 2.

In the next few years half of the world’s population will be living in regions where the fertility is at or below 2.1 – i.e. the replacement rate at which a country only has enough children to keep the population stable, resulting in a slowing down of population growth and decreasing populations in some countries.

A rich country like Germany with a declining fertility level may well see a decline in population from its present 80mn down to 75mn over the same 40 year time period as Ethiopia’s skyrockets.

It’s reliably predicted the next billion population increase to 8bn will take about 14 years and the billion after that to 9bn will take about 20 to 25 years (2050) by which time population growth may have slowed to approximately zero.

By 2100 if human fertility continues to fall below 2.1 then the 9bn population may fall to 6bn rather than continue on up to the 10bn predicted by a continuing exponential growth model.  This is positive, a fall in human population would have the benefit of enabling mankind to better manage Earth’s limited resources and help better relieve the human condition.

 

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