19 Sep 2011: Analysis

What If Experts Are Wrong
On World Population Growth?

A central tenet of demography is that global population will peak at 9 to 10 billion this century and then gradually decline as poorer countries develop. But that assumption may be overly optimistic — and if it is, population will continue to rise, placing enormous strains on the environment.

by carl haub

In a mere half-century, the number of people on the planet has soared from 3 billion to 7 billion, placing us squarely in the midst of the most rapid expansion of world population in our 50,000-year history — and placing ever-growing pressure on the Earth and its resources.

But that is the past. What of the future? Leading demographers, including those at the United Nations and the U.S. Census Bureau, are projecting that world population will peak at 9.5 billion to 10 billion later this century and then gradually decline as poorer countries develop. But what if those projections are too optimistic? What if population continues to soar, as it has in recent decades, and the world becomes home to 12 billion or even 16 billion people by 2100, as a high-end UN estimate has projected? Such an outcome would clearly have enormous social and environmental implications, including placing enormous stress on the world’s food and water resources, spurring further loss of wild lands and biodiversity, and hastening the degradation of the natural systems that support life on Earth.

It is customary in the popular media and in many journal articles to cite a projected population figure as if it were a given, a figure so certain that it could virtually be used for long-range planning purposes. But we must carefully examine the assumptions behind such projections. And forecasts that population is going to level off or decline this century have been based on the assumption that the developing world will necessarily follow the
Population estimates have assumed the developing world will follow the path of the industrialized world.
path of the industrialized world. That is far from a sure bet.

Eyeing the future, conservationists have clung to the notion that population will peak and then start to decline later this century. Renowned evolutionary biologist Edward O. Wilson has propounded what he terms the bottleneck theory: that maximum pressure on the natural world will occur this century as human population peaks, after which a declining human population will supposedly ease that pressure. The goal of conservation is therefore to help as much of nature as possible squeeze through this population bottleneck. But what if there is no bottleneck, but rather a long tunnel where the human species continues to multiply?

Population projections most often use a pattern of demographic change called the demographic transition. This model is based on the way in which high birth and death rates changed over the centuries in Europe, declining to the low birth and death rates of today. Thus, projections assume that the European experience will be replicated in developing countries. These projections take for granted three key things about fertility in developing countries. First, that it will continue to decline where it has begun to decline, and will begin to decline where it has not. Second, that the decline will be smooth and uninterrupted. And, finally, that it will decline to two children or less per woman.

These are levels now found in Europe and North America. But will such low levels find favor in the Nigerias, Pakistans, and Zambias of this world? The desire for more than two children — often many more than two — will remain an obstacle and will challenge assumptions that world population will level off or decline.

Click to enlarge
Population Growth

United Nations Population Division
Projected total fertility rate, sub-Saharan Africa, 2005-2010 to 2045-2050
In quite a few developing countries, birth rates are declining significantly. But in others they are not. In Jordan, for example, the fertility rate still hovers around 4 children per woman. Indonesia was a country that was widely acknowledged for its innovative and steadfastly pursued family planning program in the 1980s, when its total fertility rate fell to 3 children per woman. It has been hovering for some time around 2.5. In a recent survey, about 30 percent of women with 2 living children said that they wanted another child. That figure was 35 percent for their husbands.

Sub-Saharan Africa (SSA) is the region that now causes the most worry. It remains in a virtual pre-industrial condition, demographically speaking, with high fertility and rather high mortality. The UN projects that fertility will decline from a high level of 6 children per woman around 1990 and reach about 3 children per woman by 2050. Many sub-Saharan African countries have seen some decline, and today the average fertility rate is 5.2 children per woman. Should the UN’s assumptions prove correct, sub-Saharan Africa’s population would still rise from 880 million today to 2 billion in 2050.

Countries such as Congo, Kenya, Madagascar, and Rwanda have identified rapid population growth as a problem and committed sufficient resources to address it. Yet their fertility rates remain at 4.6 to 4.7 children per woman, and a future halt in fertility decline in those countries would surprise no one. But most future population projections assume a continuing decline.

Often fertility rates might decline from a higher level and then “stall” for a time, not continuing their downward trajectories to the two-child family, resulting in a higher-than-projected population. In sub-Saharan Africa,
What will it take to reach inaccessible rural populations, whose ideal number of children is quite high?
this has happened in Nigeria, where the fertility rate has stalled at about 5.7, and in Ghana, where the fertility rate is 4.1 and apparently resuming a slow decline. Very recent surveys have shown that fertility decline in Senegal has likely stalled at 5.0 children and has risen somewhat to 4.1 in Zimbabwe. Clearly, not all countries will see a continuous decline in fertility rates, and some have barely begun to drop, meaning that projected population sizes will turn out to be too low.

Fertility rates are lowest among educated, urban women who account for much of the initial decrease. What will it take to reach large, often inaccessible rural populations, whose desire to limit family size is frequently quite limited and whose “ideal” number of children is quite high? Challenges include: the logistical task of providing reproductive health services to women; informing them of their ability to limit their number of children and to space births over at least two years; low levels of literacy; the value husbands place on large families; and securing funding for family planning programs.

India provides another cautionary tale. The country is often hailed as an emerging economic power, yet 930 million people — three-quarters of India’s population — live on less than $2 per day. Some advanced Indian states, such as Kerala and Tamil Nadu, have excellent family planning programs and fertility rates of 1.8 children per woman, which will lead to declining populations in those states. But some of India’s poorest and most populous states — Bihar, Madhya Pradesh, Rajasthan, Uttar Pradesh — have total fertility rates ranging from 3.3 to 3.9. The Indian example illustrates an important trend: that the challenge of soaring populations will increasingly be concentrated in the poorest countries, and in the poorest regions of nations such as India.

The real possibility of fertility decline stopping before the two-children level is reached requires demographers, policy makers, and environmentalists to seriously consider that population growth in the
The challenge of soaring populations will increasingly be concentrated in the poorest countries.
coming century will come in at the high end of demographic projections. The UN’s middle-of-the-road assumption for sub-Saharan Africa — that fertility rates will drop to 3.0 and population reach 2 billion by 2050 — seem unrealistically low to me. More likely is the UN’s high-end projection that sub-Saharan Africa’s population will climb to 2.2 billion by 2050 and then continue to 4.8 billion by 2100. The dire consequences of such an increase are difficult to ponder. If sub-Saharan Africa is having trouble feeding and providing water to 880 million people today, what will the region be like in 90 years if the population increases five-fold — particularly if, as projected, temperatures rise by 2 to 3 degrees C, worsening droughts?

Many factors may arise to cause fertility rates to drop in countries where the decline has lagged. A rising age at marriage, perhaps resulting from increased education of females and from their increased autonomy; rising expectations among parents that their children can have a better life; decreasing availability of land, forcing migration to cities to seek some source of income; real commitment from governments to provide family planning services and the funds to do so. The list goes on.


The World at 7 Billion:
Can We Stop Growing Now?

The World at 7 Billion: Can We Stop Growing Now?
With the global impact of population growth becoming more and more evident, Robert Engelman of the Worldwatch Institute writes that a two-pronged response is imperative: empower women to make their own decisions on childbearing and rein in our excessive consumption of resources.
But we must face facts. The assumption that all developing countries will see their birth rates decline to the low levels now prevalent in Europe is very far from certain. We can also expect the large majority of population growth to be in countries and areas with the highest poverty and lowest levels of education. Today, the challenge to improve living conditions is often not being met, even as the numbers in need continue to grow.

As populations continue to rise rapidly in these areas, the ability to supply clean water for drinking and sustainable water for agriculture, to provide the most basic health services, and to avoid deforestation and profound environmental consequences, lies in the balance.

POSTED ON 19 Sep 2011 IN Forests Policy & Politics Policy & Politics Sustainability Central & South America 


In the end nature will correct this if we do not and it will not be pretty.

Posted by Jeff on 19 Sep 2011

This is the most important video you will ever see. It explains exponential growth in relatively simple terms. The planet surely will not handle the explosive growth that is occurring.


Posted by David Zilar on 19 Sep 2011

Excellent article on population growth. We often look at development only but not how to cope up with rising population. The article is very authoritative and offers good solutions.

Dr.A.Jagadeesh Nellore(AP),India
E-mail: anumakonda.jagadeesh@gmail.com

Posted by Dr.A.Jagadeesh on 20 Sep 2011

Having recently visited sub-Saharan Africa (Namibia) it seems highly unlikely to me that the land can support 4x the current population of farmers and herders without dramatic redistribution of land and global resources.

As we have seen with the recent slight decreases in economic standards in the developed countries, we the in the wealthy countries are unlikely to share well when the going gets really rough. Watch a Republican presidential debate if you have any doubts about this!

With increasing droughts and climate instability it seems that populations in Africa (and in many
other populous places) will decrease via migration and starvation. As Jeff said above, it will not be pretty.

Posted by Dave on 20 Sep 2011


Unless and until world leaders confront the real causes of our exponential population growth it will be impossible to stem the tide.

1. To the extent that Catholics, Muslims, Mormons, and socially conservative evangelicals hold to their deeply held belief to "go multiply," any leveling or reduction in population will be impossible.

2. As long as these and other religious organizations lobby against effective and cheap birth control measures, nothing will change.

3. As long as huge segments of the world's citizenry remain uneducated the issue will remain insoluble.

4. If population analysts and political "leaders" are unwilling to confront these basic causes a solution will remain out of reach.

Posted by Lynn Howard Ehrle, M.Ed, Chair- International Science Oversight Board on 21 Sep 2011

I applaud the author for illuminating standard and perhaps erroneous assumptions of standard demographic projections. But as previous commenters point out, population cannot grow forever without balancing (or negative) feedbacks kicking in. Making projections without considering feedbacks is largely an academic, overly simplistic, and likely futile endeavor. Of course considering what those feedbacks would be and how much of an effect makes a demographer's life much more complex. Tough luck.

Can't demographers begin to estimate feedbacks by quantifying feedbacks that Lester Brown is measuring such as water shortages, food production declines, climate change, disease proliferation? Without even crude feedback estimates, neither the standard demographic projections nor those mentioned by the author can offer much guidance.

Jon Kohl
Public Use Planning Consultant
Costa Rica

Posted by Jon Kohl on 22 Sep 2011

Carl Haub is a highly respected demographer. However, like many demographers and economists, he seems stuck in the middle of the twentieth century when it comes to facing reality.

Given the tremendous economic and demographic growth of the twentieth century, it is tempting to believe that it can continue. But I would bet against that happening. The current century will not be like the previous one in at least two distinctive ways.

First, we're leaving behind the era of cheap fossil fuels that drove economic growth for at least a century and a half. Economists who think otherwise should look more carefully at what geologists and others are saying, especially about future oil production. Rather than seeing a future in which economic growth continues to bring down birth rates via the demographic transition, a much more likely phenomena will be increasing death rates as food prices soar.

Second, we're also leaving behind the climatic patterns that prevailed throughout the last couple of centuries. Increasing weather extremes are assured, including both more flooding in wetter areas and longer and more difficult droughts in drier areas. These changing weather extremes, along with the end of cheap oil, are much more likely to result in higher death rates and population declines than in lower death rates and more population growth than predicted.

Until economists and demographers relinquish their death grip on worn out models and unrealistic assumptions, they will continue to argue that growth can go on forever. Even now only a couple of billion people live well on Earth; the rest struggle. By any sane measure of well-being for humans, our planet is already grossly overpopulated. Once reality sets in, the "laws of economics" will be seen for what they are: products of an era that is rapidly disappearing. It will then become clear that the "laws of nature" are not only real, but will trump those of economics.

Posted by Gary Peters on 22 Sep 2011

I hope that the society agents can make a good job getting to this people and helping them reach the number of 2 kids per woman.

Posted by Lauren D on 22 Sep 2011

good article I am also working some population development and environmental issues of india. if any oppartunity comes for attending the conference and I would share my research findings.


Dr. C.M.Lakshmana

Posted by C.M.LAKSHMANA on 22 Sep 2011

Carl Haub is an accomplished and professional demographer. Carl has a long career at the Population Reference Bureau. He is a creative, productive and effective. His piece on World Population Growth is insightful, accurate and paints a demographic future that is daunting if not Draconian.

I have a member of PRB since 1956 and have looked forward to receiving the annual World Population Data wall chart since 1962.

I have been able to get 75 heads of government to sign a Statement on Population Stabilization. We are now contracting with the heads of national family planning programs and the population policy unites within the planning commissions to prepare country specific reports on population stabilization. You can read the reports for Nigeria, Pakistan, Philippines, Egypt, Bangladesh and the states of Uttar Pradesh and Bihar by going on-line to www.populationcommunication.com. In the last few weeks we have received reports from Senegal, Yemen, Zimbabwe and an updated report from Nigeria. We will soon receive reports from Ghana, Uganda, Mali, Zimbabwe, Senegal, and Kenya. A comparative analysis of these reports is available at our website.

In sub-Sahara Africa every population has increased four times since independence, except for those that have increase five times and the TFR's are all at 5.3 - 5.7 except for South Africa. We know that 43% of the population is below 15 and all families could not have more than one child for the next 30 years to stabilize at current levels. India adds 1,500,000 new people every month and China, with a TFR of 1.5, adds 560,000 new people every month. There is an enormous momentum built into the age profiles.

Carl Haub has provided an insightful and valuable contribution and deserves congratulations for an excellent article.

Bob Gillespie
Population Communication

Posted by Robert Gillespie on 23 Sep 2011

It's so hard to get a grip on what to do about the planet. "Experts" say one contradictory thing or another. How much will population rise? After all is said and done, I do not know. But few will argue that it isn't already too large, or that the pattern of consumption is not already too high for our too high numbers. So I keep proposing another kind of population growth: the population of trees. Why isn't it more apparent that a vast number of trees can produce many environmental benefits that ameliorate our overpopulation and overconsumption? In this mysterious world, I have found that doing something beneficial that is a low hanging fruit (like planting trees) usually leads to a way to harvest those at a higher location.

Posted by Trevor Burrowes on 23 Sep 2011

This article did not discuss the impact of emmigration in relation to population growth. What consequences will the developed countries expect when the seams of the third world begin to burst.

Posted by Gino on 25 Sep 2011

You raise a good point but you forget about the rapid rates of urbanization that are taking place in the world's poorest regions, and how significant of an affect this trend has on birth rates.

The high birth rates you mentioned are true mainly in families in rural areas; populations that are rapidly, as conditions get worse, moving to cities in search for alternative livelihoods.

As I'm sure you've looked at the numbers, beyond the regions that you mentioned all populations are in decline, that is, birth rates lie below 2.1 children per family. What the world will really need to be concerned with is a population crash, not and explosion.

Posted by Nick Murray on 25 Sep 2011

Re: Nick Murray:

"What the world will really need to be concerned with is a population crash, not and explosion. "

Are we talking about catastrophic, sudden population decrease? If not, why is population decrease undesirable? 7 billion people is too much already. Besides, rich countries, especially the USA, should be exporting "appropriate technology" to rural communities throughout the world as a way to make rural life richer and keep people from flooding the cities.

Posted by Trevor Burrowes on 29 Sep 2011

Thanks for this informative and profound article! Just the other day, I found a cool interactive animation on a related topic: Where will the 7 billionth baby be born, under which conditions will it grow up... ?

Best, Juliet

Posted by Juliet Winderlich on 02 Oct 2011

Peak Oil will be followed closely by Peak People. Half the world's population is urban where there are no resourced, and everything must be imported.

Petroleum is everywhere along the food chain a lynchpin. Fossil fuels are key for both energy and climate change. The fall must be sudden and precipitous.Soon.Please note the experience of the reindeer herd on St. Matthew Island, 1944 to 1966.

Posted by charles MacArthur on 02 Oct 2011

Carl is to be congratulated for raising the very real possibility that the newest "high-fertility" demographic projections may be the ones that actually unfold (factor in amazing medical advances that continue to reduce mortality, for example, along with two decades of research that have already achieved six-fold life-extension results in laboratory organisms).

Having said that, earth's planetary carrying capacity (not just food and assorted "running-out-of" suppositions, but also daily worldwide avalanches of societal and industrial wastes along with sheer levels of physical eradication of earth's biospheric life-support machinery) is on the order of TWO billion or less if everyone is to enjoy a US/Western European standard of living.

In which case, UN high-fertility projections of 15.8 billion by century's end are the demographic and biospheric equivalents of a collision trajectory with a near-earth asteroid.

If such an asteroid were on a collision trajectory with the earth, NASA and international space agencies would begin immediate efforts to "nudge" it out of its collision trajectory, but that "nudging" would have to BEGIN while the object remains far enough away for the efforts to have an effect.

For us to nudge our demographics out of the 15.8 billion collision trajectory, the necessary nudging must begin NOW in the world's remaining high-fertility and least-developed LDCs, for every hour, day, and week that pass, humankind and our planet will find that population momentum increasingly locks us into almost inescapable humanitarian, civilizational, and biospheric outcomes.

Posted by Shale on 20 Oct 2011

I find it interesting that scientists fight for causes at opposite ends of the spectrum. At one end, environmental scientists fight to preserve and protect the earth, which includes stemming the growing world population (mostly in underdeveloped countries, where women do not have access to birth control). At the opposite end, researchers fight to lower the death rate, to prolong lives for as long as possible by curing cancer, and to cure fertility issues among the developed nations' wealthy who want children.

Developed nations could aid the underdeveloped nations in their development, providing better sanitation and living conditions, and educating women on reproductive health and regulation. This aid could speed their decrease in fertility rate. It seems obvious to me that bettering the quality of life in developing nations, and at the same time educating them on reproductive issues, is the best way to quell the steeply rising world population. However, in articles such as this one, people are spoken of as if we were an invasive species. As a Nature editor stated, as countries become more industrialized, their populations level off (perhaps still increasing a small amount) (http://www.nature.com/nature/journal/v460/n7256/edsumm/e090806-10.html). It surprises me that environmentalists do not outright support movements such as the Voluntary Human Extinction Movement (http://www.vhemt.org/). That would indeed solve the energy crisis, the CO2 problem, and the other environmental problems attributed mainly to the human population. Too often it seems that scientists forget the dignity and beauty of the human race. As a biology student about to begin medical school, I cherish human life. I hope that as a race, we are able to “achieve equilibrium” in the next few hundred years, as the UN report predicts (http://www.un.org/esa/population/publications/longrange2/WorldPop2300final.pdf).

Posted by Autumn on 15 Apr 2012

I have no problems working for environmental solutions to world population increases but we seem to be missing the point. The world is not short of food or resources it's corrupt governments which stave their population and failed to plan. Fail to decrentralise and make cities overload with people.

The human race is smart enough to overcome all problems with a growing world population yet its the United nations those government which represent us are letting the whole world down by living in denial. They cannot even come to an acceptable agreement on global warming what a joke.

Posted by Anthony Craig on 10 Jun 2012

As I understand it, we're at or near the peak in terms of the number of girls 0-14, which means the global population peak can't be far behind.

Posted by Adam on 26 Oct 2012

I value life also. And I value that we are humans. But where's the sense of living in a giant suburb or slum across all the liveable land on the earth? It might become a reality if we don't do something about it. Think about nature. Think about the planet.

Posted by Ashvir Singh on 15 May 2013

Comments have been closed on this feature.
For more than 30 years, Carl Haub was senior demographer at the Population Reference Bureau (PRB), a U.S.-based nonprofit focused on global population, health, and environmental issues. A specialist in the compilation and analysis of demographic data and dissemination, he held the PRB’s Conrad Taeuber Chair of Population Information. His research and writing has been published in numerous journals and publications.



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