CONFRONTING A SURFEIT OF PEOPLE: REDUCING GLOBAL
HUMAN NUMBERS TO SUSTAINABLE LEVELS
An essay on population two centuries after Malthus
J. KENNETH SMAIL
Department of Anthropology, Olof Palme House, Kenyon College, Gambier, Ohio 43022, USA
(e-mail: [email protected]; fax: 740 427-5815; tel.: 740 427-5812)
(Received 26 June 2001; accepted 18 February 2002)
Abstract. It has become increasingly evident over the past several decades that there is a growing tension
between two seemingly irreconcilable trends: (1) moderate to conservative demographic projections that
world population size could easily reach 9 billion (or more) by the mid-to-late twenty-first century; and
(2) prudent and increasingly reliable scientific estimates suggesting that the Earth’s long-term sustainable
carrying capacity (at an ‘adequate to comfortable’ standard of living) may not be much greater than 2–3 billion.
I therefore argue that it is now time – indeed, past time – to develop and implement a set of well-conceived,
clearly articulated, broadly equitable and internationally coordinated sociopolitical initiatives that go beyond
merely slowing the growth – or even the stabilization – of global human numbers. After summarizing a number
of ‘inescapable realities’ that the human species must soon confront, and notwithstanding the considerable
difficulties involved in establishing rational and defensible global population optimums, I conclude with
several suggestions relevant to the next logical step: how best to bring about a very significant reduction in
global population size over the next two to three centuries. To the extent that there is still time to choose
whether this dramatic decrease will be under conscious control or essentially chaotic, these proposals are
cautiously optimistic.
Key words: carrying capacity, environmental limits, global population optimums, human demography.
Stretch a bow to the very full
and you will wish you had stopped in time.
Lao-Tse
1. Defining the issue
The central point of this essay is simply stated. Within the next half-century, the
human species must have firmly in place a fully operational, flexibly designed,
essentially voluntary, broadly equitable and internationally coordinated set of initiatives focussed on significantly reducing the then-current world population by
at least two-thirds to three-fourths. In simple numerical terms, this translates into
reducing global human numbers from roughly 9 billion in 2050 to somewhere
around 2–3 billion by the late twenty-second/early twenty-third century. Given that
even with the best of intentions it will take unusual patience, consummate diplomatic skill, exceptional administrative talent and considerable time (probably on
the order of 25–50 years) just to develop and fully implement such an undertaking,
Environment, Development and Sustainability 4: 21–50, 2002.
© 2002 Kluwer Academic Publishers. Printed in the Netherlands.
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it is important that the process of voluntary consensus building – local, national and
global – begin now. If humanity collectively fails in this effort, it seems likely that
nature’s even harsher realities will almost certainly be imposed.
The demographic (and mathematical) inevitability that global population will
continue its dramatic increase over the next two generations, the high probability
that this numerical increase will exacerbate still further the systemic problems that
already plague humankind (economic, political, environmental, social, moral, etc.),
and the growing realization that the Earth’s long-term carrying capacity may only
be sufficient to sustain a global human population in the 2–3 billion range (at an
‘adequate to comfortable’ standard of living), only reinforces this sense of urgency.
There are, however, hopeful signs. In recent years, humanity has finally begun to
come to terms with the fact that the consequences of the twentieth century’s rapid
and seemingly uncontrolled population growth will soon place us – if it has not
done so already – in the midst of the greatest crisis our species has yet encountered.
Consider the following thought experiment. Take any late twentieth/early
twenty-first century problem, whether political, economic, environmental, social
or moral, and ask whether its solution would be made easier – or more difficult –
by a rapidly growing population. Or conversely, imagine trying to resolve – or at
least accommodate to – these same problems in a context where global and/or local
populations have either stabilized or slowly begun to decline. Or consider the following challenge posed by Bartlett (1998: 3): “Can you think of any problem, on
any scale, from microscopic to global, whose long-term solution is in any demonstrable way aided, assisted or advanced by having larger populations at the local
level, the state level, the national level or globally?” Or finally, might it be legitimate
to ask whether the Earth suffers not so much from a ‘shortage’ of resources as it
does from a ‘longage’ – or surfeit – of people (Hardin, 1975; 1999: 38)?
In what follows, I take the position that rapid population growth during the past
century has played a central role in causing, or in further exacerbating, the numerous
systemic problems that currently face our species. Although recognition of this
fundamental fact has been slow in coming, there is now a growing realization that
‘demographic fatigue’ can not only overwhelm the efforts of many less-developed
nations, particularly those whose populations and corresponding infrastructural
needs double (or more) every generation, but can also sap the strength of even the
most robust and stable political systems (Brown et al., 1999: 111–137). I then argue
that truly effective long-term solutions to these systemic problems will depend
significantly on whether or not humanity will be successful – over the next two
centuries – in initially slowing, then stabilizing, and subsequently reversing our
current upward demographic trajectory.
I thus begin with the following general propositions: (1) that there are indeed finite
limits to global human numbers; (2) that these limits may already have been reached
(or soon will be); and (3) that population stabilization and perhaps even significant
reduction are not only desirable but probably inevitable. However, as is usually the
case, the devil is in the details, and there is obviously considerable disagreement
about appropriate means to this end. While I (and numerous others) tend to focus on
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23
population growth as the primary (or ultimate) causal mechanism underlying many
if not most of our current difficulties, there are those who regard such growth as the
(proximate) consequence, or outcome, of the operation of various other factors. As
with so many problems of this nature, the reality of course is probably somewhere
in between, the synergistic result of numerous feedback mechanisms, both positive
and negative, operating in a complex causal network.
It is important to emphasize at the outset that the principal thrust of this essay
is directed toward matters specifically concerned with population growth itself:
(1) describing the global nature of the problem; (2) discussing the difficulties
involved in establishing optimums; and (3) suggesting approaches that might bring
about a future cessation, and subsequent reversal, of this growth. I do however
recognize, and will spend considerable time discussing, that there are two other
key issues that are almost impossible to separate from these primarily demographic
concerns: first, continued growth in per capita energy and resource consumption
(and growing disparities between rich and poor); and second, efforts toward much
greater efficiency, sustainability and prudence in energy production and resource
utilization.
Finally, to the best of my knowledge, my chief claim to originality stems primarily
from my willingness, in several published essays over the past decade (Smail,
1995; 1997a–c; 2000; 2001; 2002), to speak more openly and candidly than has
heretofore been the case about the next logical step beyond population stabilization.
Specifically, I refer here to my central thesis: that a significant decrease in global
human numbers appears to be a necessary – and perhaps inevitable – consequence
of a century-long period of ‘explosive’ population growth that now shows numerous
signs of having already exceeded the Earth’s long-term optimal carrying capacity
for our species.
2. Ten inescapable realities
In order better to appreciate the scope and ramifications of what is still a ‘partly
hidden’ crisis, perhaps the greatest evolutionary/ecological hurdle that our species
has yet encountered, I shall briefly call attention to ten fundamental, incontrovertible
and inescapable realities that must not only be fully understood but soon confronted.
The first five of these broad-based empirical observations focus on various demographic projections and concerns, while the latter five pertain to the finite ecological
(and other) limitations inherent in any discussion of global carrying capacity.
2.1. Five fundamental demographic observations
First, during the century just completed, world population grew from somewhere
around 1.6 billion in 1900 to slightly more than 6 billion in the year 2000, an almost
fourfold increase in but 100 years. This is an unprecedented numerical expansion. Throughout human history, world population growth measured over similar
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100-year intervals has been virtually nonexistent or, at most, modestly incremental;
the rate of increase has only become markedly more pronounced within the last
few hundred years (becoming exponential in appearance if not in reality). To illustrate this on a more easily comprehensible scale, human population growth during
the 1990s alone amounted to nearly 0.9 billion, an astonishing increase (of nearly
20%) in but a single decade. Just by itself, this 10-year increase is equivalent to the
entire global population in the late eighteenth century (barely 200 years ago) and is
approximately triple the estimated world population (ca. 300 million) at the height
of the Roman Empire. It is a chastening thought that even moderate-to-conservative
demographic projections suggest that a comparable rate of increase, approaching
0.8 billion per decade, will continue well into this century. This means that the
current global total of 6.2 billion (in the year 2002) could easily reach 9 billion or
more by mid twenty-first century, an increase of 50% in but two generations.
Second, even if a fully effective program of zero population growth (ZPG) were
to be implemented immediately, by limiting human fertility to what demographers
term the replacement rate – roughly 2.1 children per female in the developed world,
and slightly higher elsewhere – global population would nevertheless continue its
rapid rate of expansion. In fact, demographers estimate that it would take at least
two to three generations (50–75 years) at ZPG fertility levels just to reach a point
of population stability, unfortunately at numbers considerably higher than those at
present. This powerful population momentum results from the fact that an unusually
high proportion (nearly one-third) of the current world population is under the
age of 15 and has not yet reproduced. Even more broad-based population profiles
may be found throughout the developing world, where the under-15 age cohort
often exceeds 40% and where birth rates have remained high even as mortality
rates have fallen. While there is clear evidence that fertility rates have indeed been
declining over the past several decades, not only in the developed world but also in
various parts of the less-developed world, it is important to recognize that the current
composite fertility rate for the less-developed world – excluding China – is still
nearly double (ca. 3.7) that needed for ZPG (Population Reference Bureau, 2000).
Third, in addition to fertility levels, it is essential to understand that population
growth is also significantly affected by changes in mortality rates. In fact, demographic transition theory suggests that the earlier stages of rapid population expansion are typically fuelled more by significant reductions in death rates (i.e. decreased
childhood mortality and/or enhanced adult longevity) than by changes in birth rates.
Nor does recent empirical data suggest that average human life expectancy has
reached anywhere near its theoretical upper limit, in either the developing or developed worlds. Consequently, unless there appears a deadly pandemic, a devastating
world war or a massive breakdown in public health (or a combination of all three),
it is obvious that ongoing global gains in human longevity will continue to make
a major contribution to world population expansion over the next half-century,
regardless of whatever progress might be made in reducing fertility.
A further consequence of this continuing trend is the fact that most national
populations will inevitably get ‘older’, with mean ages in the 35–40 range and
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perhaps as many as 20–25% of their members over age 60, as both mortality and
fertility rates decline and human numbers (hopefully) reach stable or reduced levels.
Not surprisingly, each of these aging populations will develop its own unique set
of problems to resolve, not the least of which might be understandable – but in the
long term almost certainly misguided – ‘pro-natalist’ efforts to increase the size
and overall economic productivity of younger age cohorts not only by encouraging
higher fertility but also by permitting enhanced immigration.
Fourth, it is important to recognize that the quantitative scale, geographic scope,
escalating pace and functional interconnectedness of these impending demographic
changes are of such a magnitude that there are few if any historical precedents to
guide us. All previous examples of significant human population expansion – and
subsequent (occasionally rapid) decline – have been primarily local or, at most,
regional phenomena (Tainter, 1988). At the present time, given the current global
rate of increase of some 220 000 people per day (more than 9000 per hour), it is ludicrous to speak of there being any significant empty spaces left on Earth to colonize,
certainly when compared with but a century ago. And it is even more ridiculous to
suggest that ‘off Earth’ (extraterrestrial) migration will somehow be sufficient to
siphon away excess human numbers, in either the near or the more distant future.
In fact, the magnitude and rapidity of this rampant and seemingly unregulated
demographic expansion, particularly in the latter half of the twentieth century, have
led some to see certain fundamental similarities between the spread of the human
species and the growth of a malignant melanoma (or other cancer). Hern (1993;
1998; 1999), Margulis (1998) and Gregg (1955) call attention to the following criteria for identifying a cancerous malignancy: (1) rapid, uncontrolled tissue growth;
(2) invasion and destruction of adjacent normal tissue; (3) de-differentiation: loss
of functional (adaptive) distinctiveness of individual tissue components; (4) metastasis: dissemination to and/or invasion of distant tissue sites; and (5) production of
toxic metabolites.
Notwithstanding a difference in scale of several orders of magnitude, humanity:
(1) has also grown explosively; (2) has invaded, destabilized and simplified numerous adjacent ecosystems; (3) has become increasingly amalgamated into a single, undifferentiated global phenomenon (agro/techno/urban civilization); (4) has
now metastasized into a monocultural ‘juggernaut’ (Grant, 1996) in the process
of spreading to (colonizing) all corners of the Earth, typically accompanied by
(5) an excessive production of ecologically dangerous waste and pollution. Based
on these similarities, Hern et al. (1998) suggest that the human species has become
a cancer – a malignant ecotumor – on the planet, “a rapacious, malignant epiecopathologic process engaged in the conversion of all plant, animal, organic, and
inorganic planetary material into human biomass or its adaptive adjuncts.” Further,
this cancerous process has increasingly been reinforced by what has become a runaway (positive feedback) relationship between continued population growth and
ongoing cultural/technological elaboration. In simplest terms, this human cancer
has the potential to significantly, and perhaps permanently, destabilize the planetary
ecosystem.
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Fifth, given the data and observations presented thus far, it becomes increasingly
apparent that the time span available for implementing an effective program of
population ‘regulation’ may be quite limited, with a window of opportunity – even
in the more optimistic scenarios – that may not extend much beyond the middle of
this century. Other projections are rather more pessimistic, allowing no more than
another 15–20 years for taking effective remedial action. In any event, while future
population trends are notoriously difficult to predict with precision (dependent as
they are on a broad range of factors), even low-to-moderate demographic projections
for the year 2050 – a little more than two generations from now – are in the 8–9 billion
range.
Several observations might help to bring these demographic estimates, and the
above-mentioned ‘limited’ time span, into somewhat better perspective: (1) the year
2050 is now closer to the present than the year 1950; (2) an infant born in 2002
will be only 48 years old in the year 2050; and (3) a young person entering the
job market in the early twenty-first century will just have reached retirement age
by the year 2050. By any reasonable standard of comparison, this is hardly the
remote future. These observations also make it quite clear that it is primarily those
already born – ourselves, our children and our grandchildren – who will have to
confront the overwhelming impact of an additional 3 billion people within the next
half-century.
2.2. Five matters pertaining to global carrying capacity
Sixth, it is extremely important to come to terms with the fact that the Earth’s
long-term sustainable carrying capacity, in terms of resources broadly-defined, is
indeed finite, despite the continuing use of economic models predicated on seemingly unlimited growth, and notwithstanding the high probability of continued scientific/technological progress. Some further terminological clarification may be
useful. ‘Long-term’ is most reasonably defined on the order of several hundred
years at least (in human terms, a minimum of 8–10 lifetimes). It emphatically does
not mean the 5–15 year horizon typical of much economic forecasting or political prognostication. Over this much longer time span, it thus becomes much more
appropriate – perhaps even essential to civilizational survival – to define a sustainable human population size in terms of optimums rather than maximums. In other
words, what ‘could’ be supported in the short term is not necessarily what ‘should’
be humanity’s goal over the longer term.
As far as resources are concerned, whether these be characterized as renewable
or nonrenewable, it is becoming increasing apparent that the era of inexpensive
energy (derived from fossil fuels), adequate food supplies (whether plant or animal),
readily available or easily extractable raw materials (from wood to minerals),
plentiful fresh water and readily accessible ‘open space’ is rapidly coming to a
close, almost certainly within the next half-century (Giampetro and Pimentel, 1993;
Youngquist, 1997; Brown et al., 1999; Pimentel et al, 1999; Grant, 1996; 2000).
In addition, the consequences of future scientific/technological advances – whether
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27
in terms of energy production, technological efficiency, agricultural productivity
or creation of alternative materials – are much more likely to be incremental
rather than revolutionary, notwithstanding frequent and grandiose claims for the
latter.
Seventh, it is becoming increasingly apparent that much of the current rhetoric
about ‘sustainable growth’ is at best a continuing exercise in economic selfdeception and at worst a politically pernicious oxymoron. Almost certainly, working
toward some sort of steady-state sustainability (Daly, 1996) is much more realistic
scientifically, (probably) more attainable economically, and (perhaps) more prudent
politically. Assertions that the Earth might be able to support a population of 10, 15
or even 20 billion people for an indefinite period of time at a standard of living superior to the present are not only cruelly misleading but almost certainly false. Rather,
extrapolations from the work of a growing number of ecologists, demographers
and numerous others, including even a few prescient economists (Daly and Cobb,
1994; Daly, 1996), suggest the distinct possibility that the Earth’s true (optimal)
carrying capacity – defined simply as humans in long-term adaptive balance with
their ecological setting, resource base and each other – may already have been
exceeded by a factor of two or more.
To the best of my knowledge, there is no clear-cut or well-documented evidence
that effectively contradicts this sobering – perhaps even frightening – assessment.
Consequently, since at some point in the not-too-distant future the negative ramifications and ecological damage stemming from the mutually reinforcing effects
of excessive human reproduction and overconsumption of resources could well
become irreversible, and because there is only one Earth with which to experiment,
it is undoubtedly better for our species to err on the side of prudence, exercising
wherever possible a cautious and careful stewardship.
At the very least, economic analyses (and future projections based on these
analyses) should not be formulated without taking the Earth’s finite physical and
ecological limitations into account. It should by now be obvious that continued
economic growth – surely the dominant political mantra of the twentieth century –
has had significant social and ecological consequences, many of which have been
negative. And it should further be obvious that the (often hidden) ‘external costs’
of today’s economic activity, costs not only of production but also of consumption,
pollution, conservation and irretrievable loss (unavoidable ‘wastage’), must be fully
factored in. After all, these ‘externalities’ are costs borrowed from what some have
termed finite natural capital, the profligate use and continued degradation of which
will surely have a considerable effect on the quality of life in future generations. Put
simply, in the real world of physical limits and biological constraints, in contrast
to the theoretical world of monetary analysis, neither nature nor the future can be
‘discounted.’
Eighth, only about 20% of the current world population (ca. 1.2 billion people)
could be said to have a ‘generally adequate’ standard of living, defined here
as a level of affluence roughly approximating that of the so-called ‘developed’
world (Western Europe, Japan, North America, Australia, etc.). The other 80%
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(ca. 5.0 billion), including most of the inhabitants of what have been termed the
‘developing nations,’ live in conditions ranging from mild deprivation to severe
deficiency. Despite well-intentioned efforts to the contrary, there is little evidence
that this imbalance is going to decrease in any significant way, and a strong likelihood that it may get worse, particularly in view of the fact that more than 90% of all
future population expansion is projected to occur in these less-developed regions
of the world.
In fact, there is growing concern that when this burgeoning population growth in
the developing world is combined with excessive or wasteful per capita energy and
resource consumption in much of the developed world, widespread environmental
deterioration (systemic breakdown) in a number of the Earth’s more heavily stressed
ecosystems will become increasingly likely. This is especially worrisome in regions
already beset by short-sighted or counterproductive economic policies, chronic
political instability and growing social unrest, particularly when one considers that
nearly all nations in the less-developed world currently have an understandable
desire – not surprisingly expressed as a fundamental right – to increase their standard
of living (per capita energy and resource consumption) to something approximating
‘first world’ levels.
Ninth, to follow up on the point just made, the total impact of human numbers on the global environment is often described as the product of three basic
multipliers: (1) population size; (2) per capita energy and resource consumption
(level of affluence); and (3) technological efficiency in the production, utilization and conservation of such energy and resources. This relationship is usually expressed by some variant of the now well-known I = PCT equation:
Impact = Population × Consumption × Technology (Holdren and Ehrlich, 1974;
Ehrlich and Ehrlich, 1990; Hardin, 1992). This simple formula enables one to
demonstrate much more clearly the quantitative scope of humanity’s dilemma over
the next one hundred years, particularly if the following projections are anywhere
near accurate: (1) that human population could almost double over the next century, from our current 6.2 billion to perhaps 10–11 billion; (2) that per capita global
energy and resource demand could easily grow four, six or even eightfold during
the same period, particularly if the less-developed nations are successful in their
current efforts to significantly improve their citizen’s standard of living to something approaching developed-world norms; and (3) that various ‘new technologies’
applied to current energy and resource inefficiencies might be successful in reducing per capita consumption by as much as 50–75%, in both the developed and
developing worlds.
Given these more-or-less reasonable estimates, and factoring them together
as per the above formula, the conclusion seems inescapable that the human
species’ ‘total impact’ on the Earth’s already stressed ecosystem(s) could easily
quadruple (or more) by the mid/late twenty-first century. This impact could be
even greater if current (and future) efforts at energy and resource conservation
turn out to be less successful than hoped for, or if (as seems likely) the mathematical relationship between these several multipliers is something more than
REDUCING GLOBAL HUMAN NUMBERS TO SUSTAINABLE LEVELS
29
simply linear. Consider, for example, the following scenario provided by Myers
(1997):
Per capita consumption worldwide has increased by 3% per year during the past quarter century, so
it is reasonable to suppose that people in the future will want it to increase by at least 2% per year
(provided it can be sustainable). Per capita consumption would then double in 35 years, quadruple
in 70 years and increase eightfold by 2100. . . Were global population to reach 11 billion people
by 2100, total consumption would (then) expand 15 times – an amount surely unsustainable given
available stocks of nonrenewable natural resources and given the Earth’s limited capacity to absorb
pollution among other forms of waste. Even a low-variant projection for global population, 6.0
billion by 2100 (albeit after a mid-century peak of 8.0 billion) would leave consumption soaring
8.4 times.
It is, therefore, very important to keep a close watch – for harbingers of future trends
and/or problems – on current events in the growing group of nations now experiencing rapid economic development and modernization, with particular attention being
given to ongoing changes in India and China, two states whose combined size represents nearly half the population of the less-developed world (Brown, 1995; Gardner,
1996).
Tenth, and finally, there are two additional considerations – matters not usually
factored into the I = PCT equation – that must also be taken into account in
any attempt to coordinate appropriate responses to the rapidly increasing global
environmental impact described in points 6 through 9 above. First, given current
and likely ongoing scientific uncertainties about environmental limits and ecosystem resilience, not to mention the potential dangers of irreversible damage if such
limits are stretched too far (i.e. a permanently reduced carrying capacity), it is
extremely important to design into any future planning (or attempts at ‘guided
social engineering’) not only adequate safety margins but also a sufficient ‘systems
redundancy.’
In addition, such planning must consider yet another seemingly intractable problem. Because the human species not only shares the Earth – but has also co-evolved –
with literally millions of other life forms, the closely related issues of wilderness
conservation and biodiversity preservation must also be taken fully into account,
on several different levels (pragmatic, aesthetic and moral). In simplest terms, it
has now become a matter of critical importance to ask some very basic questions
about what proportion of the Earth’s surface the human species has the right to
exploit or transform – or, conversely, how much of the Earth’s surface should be
reserved for the protection and preservation of all other life forms (Wilson, 1992).
As many have argued, often in eloquent terms, our species will likely be more
successful in confronting and resolving these questions – not to mention the other
complex problems that are now crowding in upon us – if we can collectively come
to regard ourselves more as the Earth’s long-term stewards than its absolute masters. At the very least, such an effort will require an unprecedented commitment to
cooperation among (and across) all the branches of knowledge, from the scientific
to the spiritual, a collaboration that must be both integrative and consilient (Wilson,
1998a,b).
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To sum up, if the above ‘inescapable realities’ are essentially correct, it is obvious
that empirically justifiable, broadly equitable and realistically attainable population
goals will have to be established in the very near future. It is also obvious that these
goals will have to address – and in some fashion resolve – a powerful internal
conflict: how to create and sustain an adequate standard of living for all the world’s
peoples, minimizing as much as possible the growing inequities between rich and
poor, while simultaneously neither overstressing nor exceeding the Earth’s longerterm carrying capacity. I submit that these goals cannot be reached, or this conflict
resolved, unless and until world population is dramatically reduced – to somewhere
around two to three billion – within the next two centuries.
3. Setting population optimums
The logic underlying the above recommendation – and the statement that began
this essay – seems both inexorable and clear. It deserves both brief reiteration and
further elaboration, not only in terms of its basic empirical assumptions but also with
respect to its eventual scientific confirmation. Over the next several generations,
and beginning as soon as possible, humanity must not only take steps initially
to slow, and then to stop, the rapid growth of human numbers but it must also
begin the difficult task of significantly reducing global population size. However,
it will be very difficult if not impossible to stop current population growth short
of 9–10 billion. This is due not only to the ‘momentum effect’ but also to the
great difficulties, both diplomatic and temporal, in developing and implementing
the necessary political, economic, scientific and moral consensus about both ends
and means. Notwithstanding considerable effort over the past several decades, such
a consensus, or unified agenda, has yet to appear.
Because there is no clear-cut evidence to support assertions to the contrary, and
precious little margin for error, it is only prudent to operate from the increasingly
legitimate assumption that the Earth’s long-term carrying capacity, at what most
would define as an ‘adequate’ standard of living, is probably not much greater than
2–3 billion people. It is therefore necessary to confront the inescapable fact that
human numbers will have to be dramatically reduced, from the all-but-inevitable
9–10 billion projected for the mid/late twenty-first century to something much
smaller by the end of the twenty-second century, some 200 years from now.
Obviously, a numerical dislocation of this magnitude – whether brought about
by conscious design or by forces beyond human control – will require a massive
reorientation of human thought, values, expectations, and lifestyle(s).
Just as obviously, time is short, with a window for implementation that will
last no more than the next 50–75 years, and perhaps considerably less. A deliberate programme of population stabilization and reduction should have begun some
two or more generations ago – say in 1950, when human numbers were ‘only’
2.5 billion and demographic momentum more easily arrested – and certainly cannot be delayed much longer. For it is abundantly clear that if we do not choose
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31
to address and resolve this problem ourselves, nature will almost certainly solve
it for us, with consequences that would be at best unpredictable and at worst
unimaginable.
3.1. Four thorny problems
The difficult – though far from intractable – problems involved in establishing rational and defensible population optimums deserve further elaboration. Perhaps most
surprising is how unusual it is to find individuals – or organizations – who are
willing to state publicly and emphatically that just reaching a point of population
stability during the current century will not be enough, either to solve our nearterm difficulties or to stave off an ecological, social and demographic catastrophe
in the somewhat more distant future. The latter scenario, a cascading multi-faceted
catastrophe, will almost surely come to pass if humanity naively and/or unquestioningly accepts global population levels that are set so high – in the 12–20 billion
range – that they are clearly unsustainable over the longer term. One only has to
consider the stresses already evident at the current level of 6-plus billion to recognize that any sort of long-term stability at figures double (or triple) that number
will be well-nigh impossible to accomplish. Put most simply, there seems to be no
credible alternative to the conclusion that a very significant population reduction
must necessarily follow population stabilization.
Admittedly, setting and subsequently attaining the above-mentioned global goal –
a sustainable optimum in the 2–3 billion range by the beginning of the twenty-third
century – has a substantial inferential (subjective) component. This continuing and
often frustrating uncertainty about establishing an optimal size for global human
numbers stems from a number of overlapping and complicating factors. First,
it is quite likely that the sheer complexity, multidisciplinary nature, sociopolitical sensitivities and ongoing controversies surrounding analysis of the population problem have not only inhibited scientific research and funding but have also
elicited (in some) a form of ‘scale paralysis,’ that enervating sense of individual
and collective powerlessness when confronted by problems whose magnitude seems
overwhelming.
Second, there seems little doubt that scientific progress in ascertaining a reasonable optimum for world population size has been greatly hampered by the considerable difficulties in establishing empirically quantifiable, scientifically testable
and socioculturally acceptable parameters for what the Earth’s long-term carrying capacity – or flexibly defined ‘optimal population range’ – might actually be.
Certainly past projections have shown considerable variation, often of an order
of magnitude or more (Cohen, 1995). Unfortunately, with a few notable exceptions (Hardin, 1992; Ehrlich and Ehrlich, 1990; 1996; Grant, 1992; 1996; 2000;
Pimentel and Pimentel, 1991; Pimentel et al, 1999; Wackernagel and Rees, 1996),
many otherwise well-qualified investigators 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
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whether this scientific reticence is due to ingrained investigatory caution, concerns
about professional reputation and advancement (particularly among younger investigators), the increasingly specialized structure of the scientific enterprise itself,
personal qualms about reaching conclusions that have potentially controversial or
unpalatable sociopolitical ramifications, or other (often unspecified) ideological,
moral or religious reservations (Beck and Kolankiewicz, 2000).
To cite but one recent example, in his thought-provoking historical overview
and detailed scientific analysis of the population versus carrying capacity problem,
the theoretical population biologist Joel Cohen (1995) never quite gets around to
fully answering the question posed in his title, How Many People Can The Earth
Support? In fairness to Cohen, however, it is clear that the basic intent of his question
is primarily rhetorical, designed to bring out the many difficulties inherent not only
in addressing the overpopulation issue but also in attempting to resolve it. Cohen
succinctly summarizes these difficulties, providing (in the process) support for the
perspective I advocate here:
The human population of the Earth now travels in the zone where a substantial fraction of scholars have estimated upper limits on human population size. These estimates are no better than
present understanding of humankind’s cultural, economic and environmental choices and constraints. Nevertheless, the possibility must be considered seriously that the number of people on
the Earth has [already] reached, or will reach within half a century, the maximum number the
Earth can support in modes of life that we and our children and their children will choose to want.
(1995: 367). . . . Estimates of the Earth’s human carrying capacity are [thus] conditional on current
choices and on natural constraints, all of which may change as time passes. This view of estimates
of human carrying capacity as conditional and changing differs sharply from a common view that
there is one right number (perhaps imperfectly known) for all time. . . [It] leaves open the question
of optimal human population size: “What is the best number of people for the Earth to have?”
(1995: 362)
Cohen makes it quite clear that carrying capacity estimates (and population
optimums) are certainly not fixed. Rather, such estimates should be defined as
flexibly as possible, and will undoubtedly vary with differing (and changing) sociocultural expectations, techno-economic realities and environmental circumstances.
Although Cohen is apparently not quite as willing as I to make an explicit case for
significant population reduction, he does at least seem ready to countenance such
a possibility. In any event, his book is essential reading for anyone seeking to deal
with these difficult issues.
Third, it is patently obvious that the process involved in initially establishing and
subsequently implementing future population goals will involve making numerous
choices based on a variety of ‘qualitative’ considerations, that is, making important
policy decisions based on criteria that are not particularly amenable to a strictly
scientific (quantitative) analysis. It is therefore quite important to keep in mind that
all such quantitative and qualitative factors – whether demographic, ecological,
political, economic, sociocultural or moral – are not simply independent variables.
They are rather components of a complexly integrated system, functioning in a context where consequences (or outcomes) are often very difficult to predict from the
interaction of the parts. There is thus the distinct possibility that even with ‘good’
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33
(reliable) scientific data, the best of political and moral intentions, and unprecedented cooperation at all relevant sociocultural levels, it may take considerably
longer than 200 years to reach the above-mentioned numerical goals. And one
can only hope that the ecological and environmental damage that the Earth has
(or will have) sustained, from the nineteenth through the twenty-second centuries,
can eventually be rectified.
Fourth, and finally, certain fundamental human predispositions are also relevant,
including (1) a persistent and probably deep-seated inability (unwillingness) to give
serious consideration to a demographic future that seems quite remote from one’s
daily life and activities, not to mention a future for which there is little historical
precedent; (2) the presence of an equally deep-seated human predisposition toward
‘excess fertility’ (i.e. reproductive potential well beyond the limits that resources
seem able to support); and (3) the apparently ubiquitous human propensity toward
‘in-group’ loyalty and cohesion and ‘out-group’ suspicion and conflict (Wong,
1994), biopsychological mechanisms that reinforce cooperation among family, tribe
or nation while simultaneously fostering distrust of strangers or the ‘unknown.’
Unfortunately, this latter tendency has all too frequently been coupled with attempts,
by various real or self-perceived ‘out-groups,’ to build political strength by deliberate fertility enhancement (demographic competition) as well as territorial aggrandizement, ethnic partitioning and (on occasion) genocidal ‘cleansing’ (Parsons,
1999; MacDonald, 2000).
Each of these propensities may well be the consequences of ancient and deeprooted evolutionary adaptations, subsequently reinforced by political custom,
religious values and other cultural mechanisms. This complex and often volatile
mixture has the regrettable tendency, particularly under stressful conditions, to
elicit behaviors whose continuing presence and powerful effects must not only be
clearly recognized – but also effectively counteracted – in any future attempt to set
limits, voluntary or otherwise, on human procreation.
Notwithstanding the above uncertainties and complicating factors, the somewhat conservative global population optimum (2–3 billion) utilized in this essay is
not at all out of line with other recommendations of a similar nature. To be sure,
some estimates have been set considerably higher, typically in the 5–15 billion
range, but these more often than not turn out to be projections based on short-term
(single-factor) ‘maximums’ rather than longer-term (multiple-factor) ‘optimums.’
Conversely, other projections have been set somewhat lower (in the 1–2 billion
range), particularly those predicated on a future standard of living comparable to
that currently enjoyed by only a very few ‘first-world’ nations.
3.2. Other recent estimates in the 2–3 billion range
As indicated above, and somewhat surprisingly, there have only been a few recent
efforts to provide estimates of global (or regional) long-term and sustainable carrying capacities, and even fewer attempts to provide any sort of empirical justification
(or scientific confirmation) for these ‘projections.’ Cohen (1995) may be consulted
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for a thorough summary of efforts prior to the 1990s. Obviously, there is much
research yet to be done. The half-dozen estimates briefly summarized below – all
put forth within the past decade – are each reasonably close to the partly intuitive
2–3 billion level utilized in this essay. The implicit assumption, in each of these
estimates, is that most nations in the developing world are trying to acquire, within
the foreseeable future, an ‘adequate’ to ‘moderately comfortable’ standard of living, perhaps comparable to such developed-world nations as Spain, Italy, Taiwan
or Japan.
Perhaps the most promising approach is ‘ecological footprint’ analysis, as
recently articulated by Mathis Wackernagel and William Rees (1996). Defining
the footprint of a particular population (city, region or nation) as the total area
of productive land and water required on a continuous basis to produce all the
resources the population consumes, and to assimilate all the wastes that the population produces, wherever on Earth that land and water is located, their analyses reveal
that the current ‘footprint’ of the developed world alone – comprising but 20% of
the total global population – already exceeds the entire carrying capacity of the
planet. Or, arguing from the late-1980s conclusions of the Brundtland Commission
– which projected that a mid/late twenty-first century population of ca. 10 billion
would engender a five to tenfold increase in industrial output – footprint analysis
suggests that 6–12 Earths would be needed to sustainably accommodate a population of that size, presumably living at current developed-world standards. In sum,
preliminary ‘ecological footprint’ studies suggest that a global population of no
more than 2–3 billion, living at roughly half the current level of per capita consumption in the developed world, might be able to live sustainably over the longer
term. Costanza (2000) and Wackernagel and Yount (2000) may be consulted for a
recent and thorough discussion of these matters.
David and Marcia Pimentel, together with their collaborators, have focussed on
the interrelated issues of global food production, soil fertility, freshwater supply and
agricultural energy requirements in a broad range of publications over the past three
decades. They have recently suggested (Pimentel and Pimentel, 1997) that a global
population optimum in the 1–2 billion range would be a prudent (and attainable)
goal. Pimentel et al. (1999: 33–34) have further argued that:
With a democratically determined population control policy that respects basic individual rights,
with sound resource use policies, plus the support of science and technology to enhance energy
supplies and protect the integrity of the environment, an optimum population of 2 billion for the
Earth can be achieved. With a concerted effort, fundamental obligations to ensure the well-being
of future generations can be attained within the 21st century. . . . Although a rapid reduction in
population numbers to 2 billion could cause social, economic, and political problems, continued
rapid growth to 10 or 12 billion will result in an even [more] dire situation with potentially greater
problems. . . . We must avoid letting human numbers continue to increase to the limit of the Earth’s
natural resources and [subsequently allowing] natural forces to control our numbers by disease,
malnutrition, and violent conflicts over resources.
Obviously, reaching these figures would require a global population reduction of
some 80% to 90% over the next century or two, a ‘shrinkage’ that is somewhat
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35
larger but still of the same order of magnitude as that argued for in this
essay.
In several recent publications (1996; 1997; 2000), based on a varied set of arguments (ecological, technological, climatic, resource availability, agricultural potential, etc.), Lindsay Grant (1996: 75) has suggested that “a human population of
perhaps 2 to 3 billion could live sustainably at a decent level. This suggestion is
less radical than it sounds. It is where we were two generations ago [in the 1940s
and 1950s].” However, Grant points out further that:
There is not much time for a revolutionary change in human behavior. Barring a catastrophe,
momentum will carry human population upwards to 7.7 billion in the next 35 years, even if average
fertility in the poorest countries (the UN’s 42 ‘least developed’) should plunge by 60%. That would
be a remarkable achievement indeed[!]. . . . For the poor, a better [standard of] living is a dream
realizable only within a smaller population; for the prosperous, the preservation of decent living
standards depends on the same change. Two or three billion is not a bad target. We must not bog
down in scholastic debate as to the exact number. The [fundamental] issue is the direction. And
that must be down, and as soon as possible (Grant 1997: 203).
Both Garrett Hardin (1992) and Paul and Anne Ehrlich (1990; 1996), long-term
leaders in focussing attention on the growing dangers of overpopulation, make it
clear that not only is population stabilization a top priority but also that a considerable reduction of global human numbers is also essential. Ehrlich et al. (1993: 27)
point out that:
Were society to concentrate its efforts on improving agricultural production and distribution systems
worldwide, substantially more food could be grown than is grown today – for a while. It is doubtful,
however, whether food security could be achieved indefinitely for a global population of 10 or
12 billion. Rather, it seems likely that a sustainable population, one comfortably below Earth’s
(maximal) nutritional carrying capacity, will number far fewer than today’s 5.5 billion people [as
of 1993]; how many fewer will depend in part on how seriously Earth’s carrying capacity will have
been degraded in the process of supporting the (intervening) population overshoot.
In the UK, both David Willey and Andrew Ferguson of the Optimum Population
Trust (OPT) have developed national, regional and global estimates of optimal
population size, which they define as the population of a country “which is most
likely to produce a good and sustainable quality of life for all its inhabitants without
adversely affecting the quality of life either of people who live elsewhere or of people
who will live in future times” (Willey, 1996: 15). Integrating their own analyses with
those of others, OPT has argued for a global optimum of around 2 billion, or, if one
allows for a rather broad margin of error, an optimal range of 1.5–2.5 billion. With
respect to the latter, OPT recognizes that it will never be possible to set optima that
are ‘fixed’ for all time; rather, such optima that are identified will remain flexible
targets, subject to constant revision in the light of new knowledge and specific
circumstances (Willey, 1997; Willey and Ferguson, 1999; Ferguson, 1999).
In the US, Negative Population Growth (NPG) has labored for nearly three
decades to call public attention – by means of public interest lobbying, magazine advertisements and academic/scientific papers (The NPG Forum Series) – to
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the importance of stabilizing and then reducing both national and global population
size. To quote from a recent NPG brochure:
To believe, as many do, that we can provide a decent standard of living for ever-increasing numbers
is wishful thinking and irresponsible. Our present world population of 5.8 billion [as of 1997], and
growing by nearly 90 million per year, is poisoning our air and water, destroying croplands and
forests, wiping out species at an unprecedented rate, and setting in motion fundamental climate
changes. It is not sustainable over the long run, even at the impoverished living standards of much
of the Third World. If our planet cannot support 5.8 billion humans adequately, how can it possibly
support 10 to 14 billion – numbers that world population is projected to reach before the year 2100.
NPG believes that world population should be stabilized at no more than two billion, after an interim
period of gradual decrease in numbers.
3.3. A testable and falsifiable hypothesis
I hope it is obvious that this essay’s central argument – that there must be a very significant reduction in global human numbers over the next two or three centuries –
is presented in the form of a testable scientific hypothesis. That is, it is worded
in such a way that it is not only amenable to continued empirical confirmation
but also subject to potential falsification. The ‘quantitative core’ of this admittedly neo-Malthusian hypothesis clearly revolves around the following seemingly
irreconcilable numbers: (1) reasonably accurate projections that world population
growth will almost certainly reach 9–10 billion (or more) by the latter stages of
the twenty-first century; and (2) somewhat more tentative estimates that the Earth’s
long-term optimal (sustainable) carrying capacity, at what most would describe
as an ‘adequate to comfortable’ standard of living, may not be much greater than
2–3 billion.
This essentially empirical hypothesis may be quickly and easily rejected
(i.e. falsified) if it can clearly be demonstrated that current projections for global
human numbers over the next few hundred years will not exceed what will presumably be increasingly accurate projections of present and future optimal carrying
capacities. However, this central hypothesis is confirmed (i.e. not falsified) if future
global population size continues to exceed (by a significant margin) these same carrying capacity estimates. This ‘confirmation’ would be true regardless of whether
human numbers continue to grow at current rates, grow more slowly, stabilize or
even begin to decline.
Let me be even more explicit about this matter of hypothesis confirmation and
rejection and my choice of a conservative (low-to-midrange) global population
optimum. Even if future research shows that the 2–3 billion global carrying capacity figure utilized in this essay has been significantly underestimated (i.e. is ‘off
target’ by a factor of two or more), the argument put forth here loses little if any
of its persuasive power, nor is my hypothesis in any way invalidated. The reason
for this is simple. If it is indeed inevitable that global population size is destined
to reach 9–10 billion by the mid/late twenty-first century, even efforts to reach
stability at considerably larger population optimums would still require very significant decreases in human numbers. For example, setting a global optimum in the
REDUCING GLOBAL HUMAN NUMBERS TO SUSTAINABLE LEVELS
37
4–5 billion range – nearly double the figure recommended in this essay – would
still necessitate a very substantial reduction from a projected 9–10 billion, on the
order of 50% or more. From a practical standpoint, even this rather more ‘modest’
scenario differs little from the global reduction of two-thirds to three-fourths postulated at the beginning of this essay, and is surely more than sufficient to dramatize
the need for a profound – and immediate – response to what clearly appears to be
a looming demographic crisis.
Quite frankly, I hope my hypothesis is wrong and that various demographic optimists are correct in their recent claims that not only will human numbers begin
to show a ‘natural’ stabilization and decline somewhat sooner than expected, but
also that greatly enhanced efficiencies in energy production, resource utilization,
per capita consumption and conservation will allow for considerably larger carrying capacities (i.e. higher optimums) than we currently imagine. But this optimism is warranted only by corroborative data, that is, only if the above-mentioned
‘irreconcilable numbers’ show unmistakable evidence of coming into much closer
congruence. There are, after all, limits to humanity’s capacity to mortgage the
future.
Perhaps it is time to suggest that the burden of proof on these matters, so long
shouldered by so-called ‘neo-Malthusian’ pessimists, be increasingly shifted to the
‘Cornucopian’ optimists. In other words, for those who might be inclined to minimize the importance of (or summarily reject) the hypothesis put forth here, the
scientific burden of proof should be quite clear: What is the evidence that the Earth
can withstand – without irreparable damage – another two or more centuries during which global human numbers greatly exceed the Earth’s optimal (sustainable)
carrying capacity?
In any event, having established in this essay a ‘quantifiable and falsifiable’ frame
of reference, it seems obvious that it is now time to go one step further, and at least
begin to make the case that current rhetoric about ‘slowing the growth’ or even
‘stabilizing’ global human numbers is clearly insufficient to the task that lies before
us. Quite simply, the data suggest with increasing clarity that what will be required
for the foreseeable future – the ‘default position’ for the next two or three centuries –
is a significant reduction in human numbers, a decrease of at least 50% and perhaps
as much as 75% or more.
Perhaps naively, it is my hope that once a ‘critical mass’ of concerned and motivated people begins to make a serious, legitimate and empirically documentable
case for such a reduction, it would make it somewhat easier – or more ‘palatable’ –
for other scientists, as well as environmentalists, politicians, economists, moralists
and other concerned citizens of the planet, to speak forthrightly and with greater
confidence about humanity’s critical need for population stabilization and subsequent shrinkage. It is essential that elected public officials, civil servants at all levels
of government, academics from a broad range of disciplines, representatives of the
news media and spokespersons for national and international environmental organizations not feel as though they are committing political (or professional) suicide
by bringing such matters to public attention.
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3.4. Consumption and equity concerns
Even though I have already mentioned on several occasions the very important role
of per capita energy and resource consumption, this matter undoubtedly deserves
further discussion, elaboration and at least one illustrative example. To a certain
extent, the quantitative importance of consumption to the population/environment
dynamic can easily be demonstrated by the following manipulation of variables in
the I = PCT equation. Even if considerably enhanced technological and other
conservation-oriented efficiencies (T ) could reduce global ‘waste and pollution’
by as much as 50%, these gains would quickly be canceled out by a doubling of
population (P ). To many observers, this suggests that the most effective shortterm means of reducing humankind’s ‘total impact’ (I ) on the global environment
would be to focus on significantly reducing per capita consumption (C). This not
only could, but undoubtedly should, include efforts to reduce (or minimize) as much
as possible the very large (and in some instances growing) ‘affluence differentials’
between the developed and less-developed worlds.
Put another way, this suggests that the developed world also has a population problem of significant proportions, particularly when one considers that per capita consumption rates (and corresponding ecosystem impacts) in so-called ‘rich’ nations
may be 5, 10, 25, 50 or even 100 times greater than in those nations designated
as materially ‘poor.’ Therefore, it should not be surprising to anyone that the lessdeveloped world’s typical response to suggestions that they significantly curtail their
‘rampant’ population growth is an equally emphatic call for developed nations to
greatly reduce their ‘profligate’ consumption levels, or population, or both!
Let me elaborate somewhat on the above by making use of a frequently cited
example. The current differential in per capita energy and resource consumption
between the US and India – two large and representative multi-ethnic democracies – is usually said to be somewhere around 32 : 1 (Ehrlich and Ehrlich, 1990:
134). This means that each individual in the US has approximately 32 times the individual ‘impact’ of his or her contemporary in India. It also means that, even though
India’s population is nearly four times larger, India’s ‘total impact’ on the global
environment is nevertheless only 1/8 (or 12.5%) that of the US (1/32 × 4 = 1/8).
To take this one step further, and make a modest projection into the near-term
future, let us assume that a rapidly modernizing India manages to increase its per
capita consumption by 100% (i.e. double its overall standard of living) over the next
generation or so (25 years). Let us further assume that the US can maintain its current
standard of living while simultaneously cutting its per capita energy and resource
usage in half (i.e. reducing its consumption and waste by 50%). Other things being
equal, these assumptions suggest that the overall ‘consumption differential’ between
the US and India could decrease from the above-mentioned 8 : 1 to around 2 : 1 by
the year 2025. This considerable reduction in ‘gross national disparity’ would also
be coupled with an absolute decrease in overall consumption – for both nations
combined – of somewhere around 1/4–1/3. The consequence, of course, would be
a considerably lessened ‘global impact’ overall.
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Although this sounds like good news, and to a certain extent it is, everything is
(unfortunately) not equal. The above admittedly simplistic approximations assume
a stable population during the stated interval, when in reality both India and the US –
whose current populations number 1.05 billion and 287 million, respectively – are
projected to grow to some 1.36 billion and 338 million by the year 2025, according to
the Population Reference Bureau’s World Population Data Sheet for the year 2000.
In sum, the above ‘optimistic’ scenario, with India doubling its per capita consumption levels while the US reduces by half, should result in a modest and presumably welcome trend toward greater ‘individual equity’ between these two countries.
However, simultaneous population growth – adding another half billion people in
these two nations alone – would quickly negate any apparent savings in overall
global energy and resource consumption within the same 25-year time span. In short,
the Earth would only temporarily be any better off in terms of total global impact, and
would quickly find itself in considerably worse shape when population-stimulated
‘future pressures’ are taken into consideration (i.e. those extending beyond the
year 2025).
Given the above illustrative example, let me make a few additional observations
on matters pertaining to population growth, per capita consumption levels and
ongoing attempts to minimize as much as possible the above-mentioned ‘disparities’
between rich and poor. Certainly, if greater ‘fairness’ or ‘balance’ in the distribution
and utilization of the Earth’s finite resources (i.e. enhanced global equity) is to
be coupled with a considerably enhanced standard of living (quality of life) for
the mildly-to-severely ‘disadvantaged 80%’ of the world’s peoples, something has
simply ‘got to give.’
However, it is also becoming increasingly evident that even greatly enhanced
technological efficiencies (on a worldwide scale) and considerably reduced per
capita consumption (by nations in the developed world) will not be enough by
themselves to bring about the oft-articulated and presumably desirable goals of
greater equity and justice – particularly in a world that seems destined to add another
3 billion people within the next two or three generations. If one further argues that
humanity’s fundamental goal – indeed, ethical first principal – must necessarily be
to preserve the stability and resilience of the Earth’s integrated ecosystem(s), the
logical (and pragmatic) consequence of the above exercise seems both obvious and
irrefutable: Only a global population ‘optimized’ at a considerably reduced size
will provide the opportunity to build a much better quality of life for everyone.
Finally, a few closing comments about equity concerns may also be relevant.
I fully agree that a cooperative global effort to resolve humanity’s current crises,
populational and otherwise, will require both the perception and the reality of an
honest movement toward equity of all kinds (gender, class, ethnic, religious, economic, educational, etc.). But it is important to note that in addition to enhanced
equity for those currently alive (what might be defined as intra-generational or
‘spatial’ equity), there is also the equally important matter of equity for future generations (inter-generational or ‘temporal’ equity), and to recognize further that these
two imperatives may frequently come into conflict. In fact, given the inevitability of
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increasing tensions in the ongoing dynamic between present and future generations,
so much in evidence already, it is of crucial importance that we develop the political
and moral courage now to make the kinds of decisions that will maintain or enhance
an adequate (or perhaps even better) quality of life later on (for our descendants).
Suffice it to say that none of these decisions will be easy, either those concerned
with the beginnings of life (i.e. fertility) or those concerned with forestalling death
(i.e. mortality).
Last but not necessarily least, as many have eloquently described, there is yet
another balance that must be maintained. For the lack of a better term, this might be
described as a ‘geo-biological equity,’ establishing a balance not only between our
species and numerous other life forms (via wilderness and biodiversity preservation)
but also with the Earth itself (via conservation of the varied components of the
geosphere).
4. Prospects for population reduction
I am cautiously optimistic that the foregoing crisis can be averted, if only because all
humans – despite our many differences – share a deep-rooted ‘investment in immortality,’ an individual and collective concern for posterity. This powerful commitment
to the future manifests itself biologically (through the children we beget), socioculturally (through our relationships with others) and morally (through our religious
and/or ethical systems).
As an essential first step, our species will soon have to establish a difficult but
very necessary balance between individual reproductive rights and collective reproductive responsibilities. That is, all of the world’s peoples must come fully to terms
with the fact that a person’s (biological) right to have children must be mediated
by his or her (social) responsibility not to have too many.
Certainly, any hope for success in what will of necessity be a massive reorientation
of basic biological propensities and strongly held sociocultural expectations will
require attention not only to quantitative, but also to qualitative, issues and concerns.
In fact, it will likely be easier to elicit general agreement on the pressing need for
a significant reduction in human numbers (i.e. the quantitative dimension) than
it will be to construct the broad scale consensus on the qualitative restructuring
of individual, political, economic, social and ethical perceptions that will also be
required, particularly if such reduction is to occur by conscious human design.
4.1. Starting later and stopping at two
In pragmatic terms, the initial stabilization and subsequent dramatic reduction in
human numbers recommended in this essay could be brought about with relative
ease by establishing a worldwide fertility rate of approximately 1.5–1.8 over the
next several generations, lasting well into the twenty-second century at least (Lutz,
1994). Essentially, all that would be necessary is for couples to ‘stop at two.’ Because
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41
some women have no children, and others only one, this would rather quickly result
in an overall (sub-replacement) fertility rate in the desired range. It is important to
note that negative growth rates approaching (or even exceeding) this 1.5–1.8 level
have already been reached in a number of nation-states (primarily in the developed
world), that these low fertility levels have now ‘persisted’ (remained more or less
stable) for a generation and more, and (finally) that these fertility rates have in most
instances been attained voluntarily (without external coercion).
Certainly an important early step in this process of population reduction would be
to promote appropriate (i.e. culturally acceptable) local incentives to significantly
postpone age at marriage and/or age at first pregnancy, from (say) the mid/late teens
until at least the early to mid-20s. As many have convincingly argued, and as the
evidence has clearly shown, enhancing the educational, economic and social status
of women, as well as providing increased access to various inexpensive reproductive
technologies (i.e. contraceptive alternatives), should become an essential part of this
effort. If these just-mentioned incentives also encourage increased intervals between
births (Westoff, 1995), the almost certain consequence would be markedly smaller
family sizes coupled with a significant decrease in the number of generations per
unit time (from nearly six generations per century to fewer than four). Of course, the
exact nature of these incentives – whether economic, educational, social, political or
religious – could be as varied as the societies that create them. The important point
is that steps be taken toward their implementation now, or at the earliest possible
opportunity.
4.2. Gathering religious support
The last of the above-named incentives deserves special mention, particularly since
religious faith can provide a powerful impetus (i.e. moral affirmation and reinforcement) for positive demographic steps taken in a variety of other institutional
contexts. To be specific, it would certainly be most helpful if all the world’s major
religions (faith traditions) could adopt a clear, consistent and unified position in support of fertility limitation, population stabilization, women’s reproductive rights and
collective reproductive responsibility (e.g. delayed age at marriage, avoidance of
premarital sex, much greater prudence in childbearing, etc.). Unfortunately, there
has been a tendency for some religious groups either to ignore (or to minimize)
the importance of the population/environment issue, or even to take (pro-natalist)
moral and/or political stands against it (Ehrlich and Ehrlich, 1990). In addition, several religious faiths – including some forms of Christianity – espouse a somewhat
apocalyptic view of the future, either actively welcoming a prophetic Armageddon
or tacitly accepting its ultimate inevitability.
Certainly, from a scientific perspective, there seems little doubt that if our species
irresponsibly continues to ‘sow the reproductive winds,’ we will almost certainly
‘reap the demographic whirlwind’ over the next century or two. Given this likelihood, believers of all faiths should at least consider the distinct possibility that
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organized religion(s) could be among the biggest institutional loser(s) in whatever
social chaos these whirlwinds might unleash.
Obviously the focus of this essay (and these proposals) is more secular, seeking ways to understand and avert the growing possibility of a twenty-first and/or
twenty-second century ‘demographic Armageddon’ by: (1) clearly and forthrightly
recognizing its early signs and its probable future trajectory (if left unchecked);
(2) developing a coherent, mutually agreed upon, broadly inclusive, balanced, flexible and coordinated species-wide response; and (3) subsequently moving as quickly
as possible to implement such measures as are appropriate to bias the future in a
more realistic, and hopefully more humane, direction.
In any event, once an optimum population size comes within reach – perhaps
toward the end of the twenty-second century, when global numbers show clear
evidence of coming into balance with carrying capacity as then understood – the
negative fertility rates recommended above could then gradually increase to the
previously mentioned ZPG replacement level, or to whatever level appears to be in
the best long-term interest of our species at that time.
4.3. Competing agendas
However, it is abundantly clear, to judge by the agenda and continuing controversies emanating from the September 1994 United Nations-sponsored International
Conference on Population and Development, not to mention other conferences of a
similar nature, that implementation of significantly reduced fertility rates is inextricably intertwined with a number of very sensitive political and ideological concerns
(Westoff, 1995). Chief among these are matters pertaining to the enhancement of
gender equity; the educational and economic empowerment of women; ongoing
controversies surrounding family planning, birth control and abortion; problems of
development and modernization; differential access to resources and/or inequities
in their distribution; various forms of pollution and environmental degradation;
the implementation of effective public health measures to counteract the consequences of endemic poverty, malnutrition and infectious disease; the growth of
nationalism and ethnic/religious tensions; sporadic (military) attempts to expand
or redefine national borders; and human migration and the growing number of
political/ecological refugees.
These are all very important issues, and there is little doubt that they are frequently
interconnected in complex cause-and-effect relationships with population growth.
However, it is essential that short-term means not be confused with longer-term
ends. Put another way, the human species must be very careful not to lose sight of
the overarching and exploding demographic ‘forest’ in the midst of legitimate and
deeply felt concerns about particular political/ideological ‘trees.’
For the stark reality is this: Population stabilization and subsequent reduction is
undoubtedly the primary issue facing humanity; all other matters are subordinate.
Those concerned with these other matters, at the United Nations and elsewhere, must
REDUCING GLOBAL HUMAN NUMBERS TO SUSTAINABLE LEVELS
43
come to understand that solutions to the problems that concern them so deeply will
be far more likely – and (surely) far more lasting – in a world that is moving rapidly
and effectively toward population stabilization and eventual population decline. It is
becoming increasingly obvious that the alternative – a world inexorably expanding
toward as many as 12 billion (or more) by the end of this century – offers much
less hope for successful resolution of these matters. Quite simply, hard-won gains
in any of the above-mentioned areas of humanitarian concern, not to mention any
enhanced efficiencies in per capita energy and resource use, would almost certainly
be overwhelmed by continuing and uncontrolled numerical growth. This is similar
to what can be observed even now in those regions of the world where populational
doubling times of 25–35 years are the norm (Moffett, 1994; Ehrlich and Ehrlich,
1990). Clearly, running as fast as one can just to stay in the same place – or, even
worse, running while gradually losing ground – is a certain recipe for ‘demographic
fatigue’ (Brown et al., 1999).
In fact, to judge by the available evidence, it is entirely possible that the conventional wisdom of the past fifty years – particularly to the extent that this ‘wisdom’
has been characterized by large-scale economic aid (transfers of wealth) and liberal immigration policies (transfers of people) – has done more to stimulate rapid
population growth than inhibit it (Abernethy, 1993; 1996). It is almost as if a demographic Parkinson’s Law has been in effect, to wit: ‘Births tend to expand to fill
the perceived socioeconomic space.’ In other words, when the true limits of this
perceived space are obscured at the local level by overly generous international
aid and relatively easy opportunities for emigration, the unfortunate demographic
result may all too often have been counterproductive incentive structures, creating reproductive contexts in which local fertility rates have sometimes tended to
increase rather than diminish.
4.4. Coordinating the effort
This leads to a crucial final point – the ineluctable fact that in our multinational and
politically fragmented world, solutions cannot be imposed from without. Ultimately,
both individually and collectively, the people of each sovereign state must come to
terms with, and subsequently resolve, their own unique demographic and consumption problems, hopefully motivated not only by an increasing awareness of global
realities but even more by their local consequences. In this regard, given the limited
time available and the excruciatingly difficult decisions that must be made, it is
daunting to realize that population problems are often the most pronounced in areas
of the world where national sovereignty – and the requisite political, economic,
and social stability – is most tenuous (Kaplan, 1994; Connelly and Kennedy, 1994;
Smith et al., 1998).
Clearly, if the argument put forth here is reasonably accurate, and global population size does indeed show unmistakable evidence of greatly exceeding the Earth’s
optimal carrying capacity, it will be incumbent upon our species to take whatever
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humane steps might be appropriate and/or necessary to bring these divergent numbers into much greater congruence. Obviously, considerable emphasis should be
placed on such basic issues as reducing fertility, decreasing per capita consumption
and enhancing technological efficiencies, as well as implementing with all deliberate speed the appropriate political, economic, environmental, social and ethical
‘structures and strategies’ necessary to reach these goals. Particular emphasis should
be placed on: reducing various intra-generational inequities; improving the economic and educational status of women; implementing various educational reforms
directed toward enhanced demographic and environmental ‘literacy’; bringing the
world’s major religions closer together in support of a clear and consistent position
on demographic issues; and developing a much more sophisticated understanding –
particularly among economists, political leaders and ‘humanity at large’ – of the
finite ecological limits implicit in such concepts as ‘sustainability’ and ‘optimality.’
However, to reiterate an earlier observation, at no point do I make the case – nor
do I recommend – that the political means toward the above-mentioned ‘goal’ of
significantly reduced global human numbers necessarily involves collective, interventionist, centrally administered, rigidly target-oriented, or Draconian top-down
measures implemented by some sort of supra-national world government. Rather,
such measures that are employed should be essentially voluntary, broadly equitable,
flexibly designed, locally focussed (bottom-up), primarily educational and appropriately sensitive to various cultural, ethnic, gender and religious considerations (as
well as the likelihood of deeply rooted biological inclinations and propensities).
To be sure, these measures would need to be coordinated over a lengthy period
of time (several generations) by some sort of international clearing house whose
primary function would be to provide all relevant political and other ‘entities’ –
including, and most especially, various nongovernmental organizations and public
interest groups – with accurate, internally coherent and consistent information,
both scientific and sociopolitical. Such information would be designed to address
each entity’s particular and unique demographic situation, all within the broader
context (generalized goal) of moving toward a considerably smaller and increasingly
optimal world population that might provide a better quality of life for all.
I do not at this time see the likelihood of going much beyond this level of international cooperation and coordination, the basic framework of which already exists.
Whether this sort of structure and/or strategy will be sufficient for the enormity of
the task, however, I am not prepared to answer. What I do know is that humanity
does not need any further delay in educating itself about – and subsequently confronting – these critically important issues. Our ‘window of opportunity’ may not
be open much longer.
Because of these (and other) difficulties, it remains to be seen whether humanity
will be capable of mounting a unified and lasting effort toward population ‘regulation’ (i.e. limitation and eventual reduction). Clearly, this will be an unprecedented
undertaking, an effort that must be conducted on a species-wide scale, and an
endeavor that by its very nature must be sustained for a century or more. While
posterity demands that we be successful, I am only cautiously optimistic that such
REDUCING GLOBAL HUMAN NUMBERS TO SUSTAINABLE LEVELS
45
success can be achieved by rational human forethought, or by means compatible
with contemporary social, political and ethical norms. One can only hope that these
ongoing doubts about our capacity to successfully confront these problems will
somehow serve to strengthen our resolve.
4.5. Ongoing uncertainties
I fully realize that population projections are not predictions, and as mentioned
earlier, very much hope that continuation of recent worldwide fertility declines
suggests that global human numbers could ‘peak’ (stabilize) somewhere in the
9–10 billion range during the mid/late twenty-first century, some 75–100 years from
now, and then begin a slow but steady decline. Much of this guarded optimism is
based on the assumption – but not the assurance – that certain inferences based on
the demographic transition model are empirically justified, particularly the claim
that there is a strong positive correlation between increased economic and social
well-being and steadily decreasing fertility levels. But it is entirely possible that
these assumptions and correlations are also ‘projections rather than predictions,’
leaving at least three possibilities insufficiently addressed.
First, what sorts of unpredictable and potentially deleterious instabilities might
be introduced in the meantime, as both the Earth and humanity attempt to cope with
some increasingly severe twenty-first century political, economic, environmental,
sociocultural and moral ‘difficulties and discontinuities?’ And what effect, if any,
will the ‘dislocations’ stimulated by these problems, most likely resulting in a
decrease in economic, social and physical well-being, have on the above-mentioned
declining fertility rates, or for that matter on mortality rates?
Second, even if the demographic transition model has predictive value, will fertility rates necessarily keep declining to ZPG levels or below (as significant population
reduction requires), or will they stabilize at levels that are considerably smaller than
at present, yet still modestly positive (perhaps in the 2.5–3.0 range)? As many have
asked, will the demographic ‘trajectories’ observed in the developed world over the
past century or two necessarily be the case for nations in the developing world over
the next half-century?
Third, just how large a ‘shrinkage’ (population reduction) should there be, assuming we are indeed fortunate enough to reach that critical juncture? This, of course,
is a matter which has very much to do with a set of even more difficult projections,
not so much about changes in population size but rather about the Earth’s long-term
sustainable and optimal carrying capacity – in other words, the ‘second half’ of my
central hypothesis. Until convincing evidence is presented to the contrary, it would
seem prudent to adhere to the 2–3 billion ‘global optimum’ discussed earlier.
4.6. Three sensitive issues
I have generally avoided use of the term ‘control’ whenever possible, primarily
because of the negative reactions it seems to elicit when applied to population
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concerns. However, if it is indeed the case that population growth has been ‘out of
control’ for much of the past century, and if it is further the case that my central
hypothesis – that global human numbers during the twenty-first century will greatly
exceed any realistic measure of the Earth’s optimal carrying capacity – is essentially
correct, then it would obviously be much more reasonable (in humanity’s best
interest) to try to bring this situation ‘under control’ than to do nothing at all. As I
have already indicated, my approach to population ‘control’ clearly focuses much
more on the flexible exercise of restraint than on the rigid imposition of authority.
That is, it emphasizes ‘bottom up’ equity, education, persuasion and agreed-upon
incentives rather than ‘top-down’ intervention and coercion.
Second, there are (fortunately) only two relevant factors to be considered vis-a-vis
population growth at the global level: mortality rates and fertility rates. Since
increasing the former is hardly a solution that anyone might seriously want to consider, an ethical ‘non-starter’ as it were, I have obviously concentrated on decreasing
the latter, as has nearly everyone else. However, this particular limitation permits
me to mention (parenthetically) that by concentrating on world population growth,
I have been able to avoid dealing with the difficult and almost invariably sensitive
issue of immigration, a topic that has all too often (and perhaps unfortunately)
been regarded as an untouchable ‘third rail’ in discussions about population growth
(or regulation) at the national level. I would only suggest that the sooner it becomes
possible to reduce trans-national migration rates to very modest levels (i.e. to a
point where immigration and emigration rates are close to parity), the better it will
be for all concerned, not only politically and economically but also (and especially)
environmentally.
Third, there have been several recent attempts to portray population decline in a
negative light, making use of such easily remembered catch-phrases as population
implosion, population depletion and birth dearth (Eberstadt, 1997; Wattenberg,
1997). Others have (even) gone so far as to equate such decline with the possibility
of ‘demographic suicide.’ Given the fact that ‘below replacement’ fertility levels –
typically in the 1.25–1.75 range – have now become the norm for a significant
number of developed-world nations, perhaps it is not surprising that some have
begun to sound the alarm, engaging in economic handwringing, political posturing
and (in some instances) utilizing language with thinly veiled nationalistic (or even
eugenic) undertones. However, as Bouvier and Bertrand (1999: 142) point out,
“rather than expressing concern about population decline (or more specifically
falling fertility), we should be pleased with current developments and hope they
continue for some time to come.” In other words, while excessively low fertility
levels (less than 1.50) continued over several generations would indeed create some
interim short-term difficulties, it is important to keep in mind that the alternative –
continued and unchecked population expansion, as repeatedly emphasized in this
essay – could well result in irresolvable if not utterly catastrophic problems over
the longer term.
Surely it would be better to confront the challenge of population stabilization and
subsequent shrinkage early on, instead of doing nothing and subsequently running
REDUCING GLOBAL HUMAN NUMBERS TO SUSTAINABLE LEVELS
47
the danger of population ‘overshoot and collapse,’ that is, the possibility of a major
ecological and sociopolitical breakdown under the weight of an unsustainable (and
perhaps irreversible) demographic overload (Catton, 1980). The so-called birth
dearth, or population implosion, is thus not so much a short-term problem as it
is an unavoidable – even welcome – way-station on the road to a longer-term
demographic and ecologic resolution. Finally, should future circumstances warrant,
it should always be remembered that fertility rates – and for that matter immigration
levels – are much more easily adjusted upward than downward. In the real world,
therefore, the likelihood of committing ‘demographic suicide’ would be very low.
5. Concluding thoughts
I very much hope that this essay has helped to clarify a critically important (if often
underappreciated) fact: that population growth has a significant effect on, or connection with, nearly every other issue that humanity currently faces. I hope it is also
obvious that this ‘effect’ is typically both reciprocal and mutually reinforcing, resulting in numerous and interconnected positive feedback (or deviation amplifying)
systems and subsystems. It may therefore be entirely appropriate to characterize
rapid and continuing population expansion as the primary (or underlying) cause of
many, if not most, of our growing political, economic, social, environmental and
moral difficulties.
Put most simply, until demonstrated otherwise, I would argue that unchecked or
‘insufficiently restrained’ population growth is undoubtedly the single most important feature in a complex (and synergistic) ecological, biocultural and sociopolitical
landscape. In this context, human population growth clearly occupies a central position within the ‘modern problematique,’ and as such should be dealt with much more
forthrightly, and much more promptly, than has heretofore been the case.
It is also important for our species to recognize that the process of population stabilization and subsequent large-scale contraction, particularly when coupled with
what will undoubtedly be a significant reorientation of humankind’s political, economic, social and ethical priorities (i.e. a major paradigm shift toward a more
‘steady-state’ world), will take several generations, surely amounting to a century
or more. For after all is said and done, it is only our grandchildren, and those who
follow them, who will truly know whether or not we have been successful.
More than half a century ago, at the dawn of the nuclear age, Albert Einstein
suggested that we shall require a new manner of thinking, if mankind is to survive.
Even though the aptly named ‘population explosion’ is neither as instantaneous
nor as spectacular as its nuclear counterpart, the ultimate consequences may be
just as real – and potentially just as devastating – as the so-called ‘nuclear winter’
scenarios promulgated in the early 1980s (Turco et al., 1983). As discussed earlier
in this essay, that there will be a large-scale reduction in human numbers over the
next two or three centuries appears to be inevitable. The primary issue seems to
be whether this process will be under conscious human control and (hopefully)
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relatively benign, or whether it will turn out to be essentially chaotic and (perhaps)
utterly catastrophic. Clearly, we must begin our ‘new manner of thinking’ about this
critically important global issue now, so that Einstein’s prescient and very legitimate
concerns about human survival into the twenty-first century (and beyond) may be
addressed as rapidly, as fully, and as humanely as possible.
It remains to inquire whether this power can be checked,
and its effects kept equal to the means of subsistence, without vice or misery.
Thomas Malthus
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