Three Short Pieces on Fertility

December 26, 2011 • Family Planning, Reproductive Health, Daily Email Recap

Thanks to Eric Rimmer for these three important and interesting essays.

Three Short Pieces on Fertility

The first of the three pieces is by J. Kenneth Smail, Professor of Anthropology (Emeritus), and the second two by Eric Rimmer and Andrew Ferguson.  They should appear in the OPT Journal sometime, but the subject matter is somewhat topical, with the announcement of the world population passing seven billion, and a projection by the UK Office of National Statistics that in fifteen years time the UK population will be about 70 million.  Both signify overpopulation of a similar degree.  Moreover the reason that population is growing rapidly in the USA has similar causes to the UK, which hopefully will make the pieces of wide interest.

Acknowledgements: Eric Rimmer and Andrew Ferguson would like to thank Simon Ross and Harry Cripps of Population Matters for their valuable comments on our drafts.


by J. Kenneth Smail, (Ph.D. Yale, 1976), Professor of Anthropology (Emeritus) of Kenyon College Gambier, Ohio 43022, (excerpts by Andrew Ferguson, with approval of the author, from a May 5, 2008 online article published on the Culture Change website maintained by Jan Lundberg)

It has become increasingly apparent over the past half-century that there is a growing tension between two seemingly irreconcilable trends.  On one hand, moderate to conservative demographic projections indicate that global human numbers will almost certainly reach 8 to 9 billion by mid-21st century, only two generations from the present.  On the other, prudent and increasingly reliable scientific estimates suggest that the Earth’s long-term sustainable human carrying capacity, at what might be defined as an “adequate” to “moderately comfortable” developed-world standard of living, may not be much greater than 2 to 3 billion.  It may in fact be considerably less, perhaps in the 1 to 2 billion range, particularly if the normative life-style (level of consumption) aspired to is anywhere close to that currently characterizing the United States.

As a consequence of this modern-day “Malthusian dilemma,” it seems reasonable to suggest that it is now time – indeed, past time – to think boldly about the midrange future, and to consider alternatives that go beyond merely slowing the growth, or even the stabilization, of global human numbers.  In this brief essay, I shall argue that it has now become necessary for the human species to develop and implement, as quickly as possible, a well conceived, clearly articulated, flexibly designed, broadly equitable, and internationally coordinated program focused on bringing about a very significant reduction in global human numbers over the next two or more centuries.  In simple quantitative terms, this effort will likely require a global population “shrinkage” of at least two-thirds to three-fourths, from a probable mid-to-late 21st century “peak” in the 9 to 10 billion range to a future (23rd century and beyond) “population optimum” of not more than 2 to 3 billion, or perhaps even fewer.

Obviously, a demographic change of this magnitude, whether brought about by conscious human design or ultimately by forces beyond human control, will require a major reorientation of human thought, values, expectations, and lifestyle(s).  Unfortunately, there is no guarantee that such a program will be successful.  Moreover, if humanity fails in this effort, it seems likely that nature’s even harsher realities will almost certainly be imposed.  Speaking as a professional physical anthropologist/human evolutionary biologist, it is entirely possible that this rapidly metastasizing – yet still partly hidden – demographic and environmental crisis could emerge as the greatest evolutionary/ecological “bottleneck” that our species has yet encountered.  …

Notwithstanding the numerous difficulties in addressing a problem of such complexity, it is nonetheless surprising how little scientific and public attention has been directed toward establishing empirically quantifiable, scientifically testable, and socioculturally agreed-upon parameters for what the Earth’s long-term human carrying capacity – or flexibly defined “optimal population range” – might actually be.  Unfortunately, with only a few notable exceptions, many otherwise well-qualified scientific investigators and public policy analysts have been rather hesitant to take a clear and forthright position on this profoundly important matter, certainly destined to become the overarching issue of the current century.

It is difficult to say whether this unfortunate reticence is due to ingrained investigatory caution, concerns about professional reputation and advancement (particularly among younger investigators), the increasingly specialized structure of both the scientific and political enterprises, personal qualms about reaching conclusions that have potentially unpalatable social and political ramifications, or other unspecified (and perhaps deeply-rooted) ideological, moral, or religious reservations.  Or perhaps, given its global nature and seemingly endless ramifications, the chief difficulty in dealing with the complex population/environment conundrum represents little more than a manifestation of “scale paralysis,” that enervating sense of individual and collective powerlessness when confronted by problems whose magnitude seems overwhelming.

Certainly the rough approximations of global human carrying capacity put forth during the past century show considerable variation, ranging from fewer than 1 billion to well beyond 20 billion (an order of magnitude or more).  It is, however, important to note that over the past two decades there have been a growing number of investigators and organizations who have put forth reasonably well-thought-out positions on future global population optimums.  Interestingly enough, these estimates have all clustered in the 1 to 3 billion range.  This is an important development, since it is patently obvious that it will be difficult to engender any sort of effective public response to the above-mentioned global crisis if future population goals (i.e., desired demographic optimums) continue to be imperfectly understood and poorly articulated. …

Notwithstanding our current addiction to continued and uninterrupted economic growth, surely the dominant political mantra of the 20th and early 21st centuries, it is essential for humanity to recognize that there are, after all, finite physical, biological and ecological limits to the Earth’s long-term sustainable carrying capacity (i.e., the “natural capital” that supports us).  And to recognize further that we are now drawing down on the principal, as well as the interest, of this precious “capital,” as many of these finite limits have already been reached (and in a number of instances surpassed). …

That there will be a large-scale reduction in global human numbers over the next two or three centuries appears to be inevitable.  The primary issue may well be whether this lengthy and difficult process will be comparatively benign or unpredictably chaotic.  More specifically, is modern humanity capable of a comprehensive organized effort to compassionately reduce global human numbers, or will brutal self-interest prevail – either haphazardly or selectively – resulting in an unprecedented toll of human lives?  Clearly, we must begin our “new manner of thinking” about this critically important issue now, so that Albert Einstein’s prescient and very legitimate concerns, expressed more than 60 years ago, about human (and civilizational) survival into the 21st century and beyond may be addressed as rapidly, as fully, and as humanely as possible.

Don’t speak to me of shortage.  My world is vast

And has more than enough – for no more than enough.

There is a shortage of nothing, save will and wisdom;

But there is a longage of people.   –

Garrett Hardin (1975)


by Eric Rimmer and Andrew Ferguson

Abstract:  It is evident that to avoid catastrophe the world as a whole needs to achieve a low Total Fertility Rate (TFR), but it is vain to hope that all nations will act accordingly.  Indeed the only example we have in history of a nation controlling the size of its population over a long period of time is the tiny island of Tikopia.  It thus behooves every nation to find ways of limiting its own population so as to be sustainable.  Migration can easily upset the best efforts of the indigenous population.

Demographers tend to devote their efforts to making projections about future populations as things appear to be going at present.  But what is more important is to decide where we need to be going in view of the multiple changes that are likely to decrease the planet’s human carrying capacity.  The list of those troublesome changes is long, but it includes, water shortage (as water tables are drawn down), desertification, loss of topsoil, declining fish stocks, climate change (making all farming more difficult), increasing cost of fossil fuels making fertilizers expensive, flooding (due to rapid melting of glaciers and heavy rain), rising sea levels and subsiding coastal cities (often due to water extraction).  But perhaps larger than all these will prove to be a huge decrease in the energy available to us as fossil fuels become scarce.

If these detrimental changes take substantial effect before 2100, and that is certainly on the cards, then the magnitude of the changes needed in human behaviour are apparent from Figure 1.  Let us look at some figures briefly before drawing conclusions.

The average world Total Fertility Rate (TFR) according to the World Population Data Sheet of the Population Reference Bureau is 2.5.  If with immediate effect it could be reduced to 2.0, then by 2100 world population would be about 7.6 billion.  Immediate reduction to a TFR of 1.75 would result in a 2100 world population of 5.8 billion.  A reduction to a TFR of 1.5 would result in 4.3 billion, and a reduction to 1.0 would produce a world population in 2100 of about 2.2 billion.

What is mainly going to determine which of those numbers is closest to the actual carrying capacity in 2100 is largely a matter of the extent to which we are capable of overcoming the multiple problems facing humanity, most particularly the ability to find substitutes for fossil fuels.

But taking an overview of the world as a whole is of little value, because even faced with the obvious facts of deteriorating environments, many nations will not take adequate steps to reduce the size of their population in time.  For instance, China has taken some steps but it remains in doubt if those steps will be sufficient, especially in view of its environmental problems, such as falling water tables and the danger of large scale coastal flooding of fertile land.  India still has to take action that can be shown to be effective.  Japan, which is already overpopulated, has become worried at a falling population.  This tendency to regard falling populations as a problem is widespread.  Governments and economists seem incapable of taking a long term view.  Indeed limiting population to a level that is sustainable is almost unheard of in human history.   The tiny island of Tikopia may be the only example (it continued with a policy that controlled its population for a thousand years, and probably would have continued to prosper were it not for its “discovery” by the outside world).

If all nations need individually to take steps to reduce the impact of each individual, and the size of their populations, to a sustainable level, then the fact will have to be taken on board that for some countries migration is as great a problem as is too high a TFR.  Moreover it is hard for governments to take steps to encourage their native population to a low TFR if altruistic action by their citizens to lower population – people often want more children – is being undone by imbalanced migration.

What is evident is that in order to avoid the sort of catastrophe that overtook Easter Island, nations need to consider their own carrying capacity and aim for a TFR that will get them to where they need to be.  One very important factor is the likely availability of energy, which is why the OPT Journal devotes so much space to it.

In positing that a whole population will keep to a specified TFR there is an obvious simplification, and hence errors, but it can still be illuminating to see what happens under such simplified assumptions, so let us take an example which will illustrate why it is so unrealistic to imagine that the human race as a whole will be able to control its population.

There are half a dozen countries that have managed to get their TFR down to 1.6.  Now imagine that, by some miracle of wise foresight, 80% of the world’s population achieves a steady TFR of 1.6.  In 2010, the size of that hypothetical group would be of 5.5 billion.  By 2100 it would be 3.9 billion.  About 15% of the present population has a TFR of 3.0 or greater, so, as an illustrative hypothesis, 20% of the population staying at a TFR of 3.0 is not unrealistic (except that things inevitably change with passing time).  Starting at 1.4 billion, that group would expand to 3.7 billion by 2100 (Figure 2).

Combining the populations of the two groups gives a world population of 7.6 billion by 2100.  The effect of the 20% becomes more apparent with the passing years.  By 2210, the 1.6 TFR group has decreased its size by 4.3 billion, to 1.2 billion.  But by maintaining a TFR of 3.0, the group that started as 20% of the population, would have increased its size by 6.0 billion (making it constitute 91% of a combined world population of 12.9 billion).

A further example of the extent to which an average TFR does not give an accurate projection of future populations, if there is wide variation from that average, is from one United Nations projection.  The average TFR is 2.5, and under the hypothetical concept of each woman having 2.5 children, by 2100 the world population would be 12.3 billion.  However the UN Constant Fertility variant, which must use the fertility of each group within the whole population, produces a population of 26.8 billion for 2100.

The lesson from this is clear enough, and goes to confirm the earlier assertions:  it is unrealistic to assume that a sufficiently large proportion of the world will act with foresight to get world population into balance with ecological resources.  The best that can be realistically hoped for is that some nations will have sufficient foresight to ensure that their population is of such a size that they can sustain themselves (climate permitting) in the way the Tikopians managed to achieve on a small island for at least a millennium.


by Eric Rimmer and Andrew Ferguson

Abstract:  Any substantial group of citizens feeling little responsibility for achieving sustainability through low birth rates can easily upset sterling efforts by the rest of the population.  That is illustrated here both in theory and by recent projections for the UK from the Office of National Statistics, which point a finger at immigration.

The variation in Total Fertility Rates throughout the world is substantial.  For instance, the average is 4.7 taking Africa as a whole, whereas in the European Union it is 1.6, and in the USA 2.0.  Within Africa there is wide variation;  it is often well above the average:  5.2 in Sub-Saharan Africa; 6.4 in Uganda, and 7.0 in Mauritania.  One thing which will soon become apparent is that an average TFR is somewhat misleading because of this wide internal variation.

But the most important lesson deriving from a study of Total Fertility Rates (the average number of children per woman) is that a substantial group within a population who are somewhat unrestrained in their fertility can quickly undo the ‘good work’ of another substantial group who are restraining their fertility.  Let us look at this in the context of Figure 1, which shows a world population starting at 7 billion.  We then take a look at various hypotheses.  We will focus on the figures for the year 2100, as people are somewhat unwilling to think further ahead – and perhaps with good reason as the future becomes more uncertain the further one progresses into it.

The lowest curve in Figure 1 shows how population would change were – with immediate effect – all women to have only two children – a TFR of 2.0.  Population would rise for a time due to the present age distribution, and by 2100 it would be 7.6 billion, dropping slowly.

The top curve shows how population would change were every woman to have three children – a TFR of 3.0.  The size of population would race away, reaching 18.5 billion by 2100.  These are theoretical concepts, because we are ignoring the constraints of water, food, and energy shortage, and all such things.  But the results serve to show that the ‘good work’ of those women confining themselves to two children, which give a prospect for a world of 7.6 billion by 2100, would be massively undone were a substantial number of women to have three children:  the curve below the top one shows what would happen were half the women in the population to allow themselves two children while the other half allow themselves three.  By 2100, the population would be 14.1 billion.

The next line down (it is more of a straight line than a curve) is there to illustrate the point that an average TFR does not produce the same result as combining two different TFRs.  It is impossible for each single woman to have two and a half children, but considering it as a theoretical construct, the line shows that it would result in a world population by 2100 of 13.0 billion.  The difference from 14.1 billion is not great, but in Figure 1 we are only considering variations in the TFR of 0.5 from an average of 2.5.  Were we to look at more substantial variations, which are evident in reality as mentioned in the first paragraph, the difference would be larger.  Even the 0.5 variation shows up as a substantial difference by 2210.  Figure 1 shows that by then there would be a difference of 32.0 – 19.6 = 12.4 billion between combining the two TFRs and just taking an average.  That figure can be put in the context that many authoritative estimates put the size of world population that could be sustained to modest European standards as about 2 to 3 billion.

The overarching lesson is that the efforts of a substantial portion of the population to constrain their fertility can be quickly overcome by a lesser restraint from the rest.  An illustration of this, appertaining to the UK, was reported in The Times newspaper – and in the media generally – on 27th October 2011.  It was stated there:

The report, from the Office of National Statistics (ONS), said that the population was growing rapidly and was projected to rise from 62.3 million last year to reach 70 million by 2027.

As argued in the OPT Journal over many years, the optimum population of the UK is about 20 million, so we are already starting from a very bad place, but that 20 million sets in context the projected addition of 7.7 million.  The report goes on to say:

Two thirds of the overall increase is due to immigration, either directly through new migrants arriving or indirectly through a higher birthrate to immigrant mothers.  The remaining third is because of a general increase in births and increase in longevity.

The projections are based on an assumption that net migration – the difference between those arriving and those leaving – will continue at 200,000 a year inward.

200,000 a year for 17 years amounts to 3.4 million.  Subtracting that from the 5.1 million increase which is estimated to be due “either directly through new migrants arriving or indirectly through a higher birth rate to immigrant mothers” leaves 1.7 million attributable to a “higher birthrate to immigrant mothers.”  Our government, like others before them, have stated their intention to reduce immigration, but it will be what is actually achieved that counts, rather than intentions.

The lesson of Figure 1 remains clear, namely that if our population is to be reduced to a sustainable level, not only is it necessary that the present inhabitants should attain a below replacement TFR (which is about 2.1), but that there should not be a group of citizens within society who feel no obligation to play their part in achieving sustainability.

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