World population forecast increases by 0.5 to 1 billion in just two years

…comparing either 21st century peak population or 2100 population.

Somewhere this year (October 31 says UN’s big computer) the 7 billionth human inhabitant of this planet will be born – then starting to emit his of her average annual 5 tons of CO2.

It may seem a slight worry, in embarrassing contrast with the parental happiness (that we presume). However billions of slight worries that each year help to add up to one big cumulative sustainability problem make for a different perspective. From this we wonder: is it the actual number of the forecast that should worry us – or the speed with which these forecasts keep exceeding each other?

Just two years ago the UN published its World Population Prospects 2008 Revision. In this report the world population was forecast (medium variant) to grow to a peak of 9.4 billion people somewhere before the year 2100. (In 2100 the world population would have started to decline to 8.9 billion.)

Ten days ago the UN released the World Population Prospects 2010 Revision. Now population growth will not have peaked before 2100. And there will suddenly be 10.1 billion of us at the end of the century. That is quite a margin, again, as all recent population revisions have silently surpassed each other, leading to suspect we need to practice our high school mathematics to calculate the ‘real’ world population curve.

Much of this population growth will come from ‘high-fertility’ developing countries, 39 of which are African countries, nine Asian, six lie in Oceania and four in Latin America – while some European and East Asian countries actually see population declines.

World population forecasts are in essence plausibility estimates of the actual height of the fertility number in the developing world – or the assumption that this number will decline at some point, to some extent. With a margin of just one child difference in this fertility number the UN presents the high and low variants of their prospects. By 2100 this fertility difference amounts to 9.8 billion ‘theoretical people’ separating these two scenarios: 6.2 billion in the low variant and a steady (and staggering) growth to 15.8 billion under the high variant scenario.

For the year 2050 the low, medium and high variants lead to respective world population growth towards 8.1 billion, 9.3 billion and 10.6 billion people.

To emphasize the steady pace with which the UN population forecasts keep catching up on each other: the medium variant for 2050 (now 9.3 billion) was 9.2 billion in the 2006 Revision, 9.1 billion in the 2004 Revision and 8.9 billion just 2 years before, in 2002.

Active contributors to the sustainability debate [like Fred Pearce*], who state high fertility in developing countries is not a definite problem because fertility is inherently highly variable [so it should not be regarded as a fixed number for long term projections] and that it will decline with economic development [instead of remaining high because of cultural resilience], may be ignoring the fact that this fertility variability in large-scale practice only seems to show itself in one direction: up.

*) Fred Pearce is a respected British science journalist, specialised in various sustainability issues. He is author to The Last Generation (about physical climate urgency) and Peoplequake (about population growth). These books contrast by being each other’s inverses when it comes to sharing an alarmist message. Pearce may have overstated the physical urgency [although not so much as others understate it] of the climate problem in The Last Generation – that hints our climate system would be more sensitive than it actually is, by perhaps piling up too many presumed feedback-fed tipping points. Peoplequake’s main message on the other hand seems to be that billions of extra people does not necessarily imply overpopulation – and yet another century of population growth does not imply eternal population growth.

It is nothing more than personal gut feeling that Mr. Pierce’s contributions to the demography debate (which are more recent than his publications about climate tipping points) may serve to show he is ‘not an alarmist’ on every topic – perhaps mainstreaming himself and reinforcing overall public credibility but in doing so now possibly ignoring the true urgency of another sustainability crisis, with a purely social cause.

If such psychology would apply, Pierce would join a big group of ‘sustainability professionals’ who seem much more comfortable in stressing physical problems than social ones, thereby refraining from taking part in politically incorrect blame games. That is a pity, as blaming is the most efficient route of pinpointing to the core of problems, creating space for solutions. Also lurking geographical, political and economic tensions due to increasingly large regional differences in population growth are seemingly just being ignored by the majority of senior commenters on demography trends.

It is why smaller and unassociated media may have a relatively large role to play in breaking the pc deadlocks surrounding demography – and why you will find us at Bits Of Science digging up more interesting statistics and forecasts from the World Population Prospects 2010 Revision in the weeks and months ahead.

© Rolf Schuttenhelm |

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