Archive for the 'Population' Category

A Debate about the Future of Human Population

Sunday, February 25th, 2018

David Lam is a Professor of Economics at the University of Michigan and Director of the Institute of Social Research. He is highly respected and widely published in the field of demography. His elected positions include being past president of the Population Association of America and being elected to the Council of the International Union for the Scientific Study of Population (IUSSP). Lam is truly a giant in the field of demography, and deserving of all his many honors.

Dr. Lam published an essay last year in N-IUSSP, the IUSSP’s online news magazine. Titled “The world’s next 4 billion people will differ from the previous 4 billion“, it got me riled up because I felt that Lam ignored our human life-support system–the natural world. My response, “The world in which the next 4 billion people will live“, was also published by N-IUSSP. This sparked a third, “Global population, development aspirations and fallacies” and then a fourth essay, “Thinking about the future: the four billion question”.

Here are very short abstracts of the four essays. Since I’m doing the abstracting, the abstracts may not be totally objective!

  1. Dr. Lam notes that it took just 50 years to add 4 billion people to give us the 7 1/2 billion we have now, but that it will take until about 2100 to add the next 4 billion–and then growth will probably stop. Much of this growth will be in Africa, and the people will be older. He also believes about this population growth “… the experience of the last 50 years gives room for optimism about the world’s ability to support it.”
  2. I am less optimistic, fearing that we have already used so much of the planetary resources that there will be significantly less left for those who come after us.
  3. Dr. George Martine feels that I am overly optimistic about the ability of family planning to slow population growth. Unfortunately, I agree with him! Martine had 4 concerns about the prior 2 articles: “a) the urgency of environmental threats; b) the recognition of diversity in ‘population’; c) the limitations of fertility reduction solutions; and, d) the urgency of redirecting ‘development’.”
  4. I like the way this essay starts: “The ‘population question’, central to the debate about humankind’s future since the 18th century, has slipped away from center stage and fallen into a coma in recent years.” The essay takes a critical look at some of the factors affecting population and our ability to inhabit Earth. Dr. Livi Bacci looks at climate change caused by greenhouse gas emissions, and points out that it is not just population that has increased but also the financial ability of people to purchase and use carbon-based fuels–consumption.

I welcome folks to look at these four essays and draw your own conclusions. I first read Lam’s article because I am a member of the IUSSP and subscribe to N-IUSSP, but they are available online to anyone. Just search using their titles. You can even submit a response without being a member. It is good to have a debate on these subjects that are so important to our future!



Heed this Warning

Saturday, November 25th, 2017

In 1992 the Union of Concerned Scientists published the “World Scientists’ Warning to Humanity”. Twenty-five years later it has just been updated.

Most of the Nobel Prize winners then alive and 1575 senior scientists signed the original warning. It started with the words: “Human beings and the natural world are on a collision course. Human activities inflict harsh and often irreversible damage on the environment and on critical resources. If not checked, many of our current practices put at serious risk the future that we wish for human society and the plant and animal kingdoms, and may so alter the living world that it will be unable to sustain life in the manner that we know.”

After this powerful introduction there are several headings. The heading titled “Population” states what many people (especially economists) are still denying. It starts with: “The earth is finite.”

Later in the “Population” heading you can read: “Pressures resulting from unrestrained population growth put demands on the natural world that can overwhelm any efforts to achieve a sustainable future.” I find it remarkable that those who write about “sustainable development” so often ignore this obvious fact.

This 1992 Warning had 5 points under the title “What We Must Do”. Point #3 states: “We must stabilize population. This will be possible only if all nations recognize that it requires improved social and economic conditions, and the adoption of effective, voluntary family planning.” Unfortunately this was all but ignored. In fact, just 2 years later, at the UN’s International Conference on Population and Development, delegates decided to turn the focus away from population and toward HIV and reproductive rights. This had an unfortunate effect on support for family planning programs.

So much for the past. Not too many people were aware of the 1992 document, and fewer took it to heart. Scientists have updated the Warning on its 25th anniversary in a remarkable fashion. “World Scientists’ Warning to Humanity: A Second Notice” was published last month in BioScience, a well-known journal. Although eight authors appear on the title page, the total number of signatories is huge—15,364 scientists from 184 countries! It is not too late to join this elite crew if, indeed, you are a scientist. Go to to find out more and to endorse the article. Over 3,000 people have done added their names.

The current Warning is not optimistic. Of the 9 issues treated 25 years ago, only one shows improvement. The good news is that ozone-depleting emissions (chlorofluorocarbons) are decreasing. They jeopardize the atmospheric ozone that guards us against dangerous ultraviolet radiation. The other 8 trends are all bad; these include fresh water supplies, total forest area, vertebrate species abundance and ocean dead zones. Need I also mention that the CO2 level is rising and the climate is heating up?

It comes down to two factors—population and consumption. The authors put it this way: “We are jeopardizing our future by not reining in our intense… material consumption and by not perceiving continued rapid population growth as a primary driver behind many ecological and even societal threats.”

Slowing population growth seems much more attainable than decreasing consumption, however. So many people want to manage their fertility but don’t have access to effective contraception—we must expand access to birth control here and abroad.

There is hope. The new Warning points out that pressure on politicians, especially from scientists and concerned citizens, can create change. The authors also cite the importance of changing individual behaviors such as choosing to have small families and to consume less—including moving toward a plant-based diet. They celebrate the decrease in family size throughout most of the world and praise the decrease in world hunger. They use the example of the decrease in chlorofluorocarbons as an example of what can be done when there is political will.

The Warning gives 13 steps to take in order to move in the correct direction to save our life support systems. The 12th is to revise our economy to reduce inequality of wealth and to take into account the externalities that harm our planet. The last proposes a revolutionary idea—to determine what a long-term sustainable human population might be, then to rally support to reach that goal.

Can more than 18,000 scientists make a difference in a positive direction? We have seen how much damage one person, the president of the USA, can do by moving us away from sustainability. It is time for us to heed the far-sighted Warning for our progeny’s sake.

© Richard Grossman MD, 2017

Essay distributed to two large groups of experts

Tuesday, November 14th, 2017

I am happy that an essay I wrote was distributed by the IUSSP (International Union for the Scientific Study of Population). It was then picked up and redistributed to the PERN (Population-Environment Research Network). Through the miracle of digital communications several thousand people have been able to read this–without a single piece of paper being used!

The essay was written in response to one that was published by IUSSP and written by a wonderful person, David Lam. David is optimistic about the future of the planet to support 4 billion more people. I am concerned that we have already caused so much damage and believe that the degradation will worsen unless we slow our population growth rate, and decrease our consumption. Dr. Lam’s essay is available at:

My essay is below, somewhat shortened by excluding information about a wager that Dr. Lam has with another friend, Stan Becker. The complete essay is available at:

The world in which the next 4 billion people will live

I was pleased to read Professor David Lam’s N-IUSSP essay “The world’s next 4 billion people will differ from the previous 4 billion” (Lam 2017). He outlines past, present and projected future population growth. He points out that much of the population growth will occur in Africa, and that a higher proportion will be older, if current trends continue. He also wonders “…whether the world can absorb another 4 billion people.”

As a demographer, it is appropriate that Lam should focus on humans. However, I fear that he has largely ignored the environment in which we live when he wrote this essay. I have difficulty accepting his statement: “An important source of optimism about the world’s ability to support an additional 4 billion people is the success in supporting the previous 4 billion.” My concern is that the past 4 billion have degraded natural world upon which we depend, and that this degradation will make the world much less welcoming to the next 4 billion.

A changing world (not always for the better)

I agree that the next 4 billion people will differ from the previous 4 billion as professor Lam explains, but so will the world in which those people live. Dr. Norman Borlaug understood this when he stated, in his Nobel Prize acceptance speech of 1970: “The green revolution has won a temporary success in man’s war against hunger and deprivation; it has given man a breathing space. If fully implemented, the revolution can provide sufficient food for sustenance during the next three decades. But the frightening power of human reproduction must also be curbed; otherwise the success of the green revolution will be ephemeral only. Most people still fail to comprehend the magnitude and menace of the ‘Population Monster’. …Since man is potentially a rational being, however, I am confident that within the next two decades he will recognize the self-destructive course he steers along the road of irresponsible population growth….”

Borlaug’s three decades have passed and we have seen the side effects of the “green revolution”—decreasing soil quality, decreasing forest coverage, increasing pollution (including huge anoxic ocean dead zones), rapid loss of species and, perhaps worst of all, climate change. The “green revolution” has allowed us to feed more people so that, finally, fewer people go to bed hungry. However, more food has made it possible for our human population to grow at a faster rate, despite monumental increases in reproductive health and family planning.

How can we quantify human impact?

The formula popularized by Ehrlich and Holdren (1974) gives an idea of our human impact on the earth: I = P x A x T (I = impact; P = population; A = affluence (or consumption); T = technology). Let’s look at these factors in the opposite order. We are starting to develop technology to decrease our impact, such as solar panels and more efficient vehicles, but the benefit so far from new technology is relatively small. As for the A factor, affluence, I have met very few people who actually wish to decrease their consumption. There is too much social pressure for people to increase their consumption. Furthermore, leading an affluent life is more comfortable so it has become the goal of billions of people.

Slowing population growth, on the other hand, is the “low hanging fruit” to reduce human impact P. An estimated 225 million women worldwide wish to avoid pregnancy but are not using effective contraception (Singh et al. 2014). Moreover, having fewer offspring has been shown to be the most effective way of reducing impact, using greenhouse gas emissions as a measure of impact (Murtaugh & Schlax 2009).

How can we determine to what extent human activities are degrading our planet? The best measure of planetary sustainability is the Ecological Footprint. This shows that humans are already overtaxing the planet. Indeed, it would take 1.6 planets Earth to support our human population sustainably the way we are currently living (Figure 1). Unfortunately, there is only one Earth.Schermata 2017-11-12 alle 15.11.12

This degradation of our life support system will become a grave problem as the next 4 billion people are added. There will be more people to share the resources and more people to contaminate the world with their waste products. The most visible of the latter is the climate change caused by carbon dioxide from our use of fossil fuels, but there are many other examples. Already food production systems are stretched to keep up with the addition of about 80 million people each year. With global warming, the outlook for increases in food production in some African states is poor. Feeding even 9 billion by midcentury will clearly be a major challenge.

We have been fortunate to live in this era, but I fear that the next 4 billion people will live in a world that is very different, and not so enjoyable. Current inhabitants must think more about preserving the earth for future generations.


Ehrlich P.R., Holdren J.P. 1971. Impact of Population Growth. Science 171 (3977): 1212–1217. doi:10.1126/science.171.3977.1212

Lam D. 2011. How the World Survived the Population Bomb: Lessons From 50 Years of Extraordinary Demographic History. Demography, 48(4): 1231-1262.

Lam D. 2017.  The world’s next 4 billion people will differ from the previous 4 billion. (N-IUSSP July 24, 2017)

Murtaugh P.A., Schlax M.G. 2009. Reproduction and the carbon legacies of individuals. Global Environmental Change 19: 14–20.

Singh S., Darroch J.E., Ashford L.S. 2014. Adding It Up: The Costs and Benefits of Investing in Sexual and Reproductive Health. New York: Guttmacher Institute.

Becker S. 2013. Has the World Really Survived the Population Bomb? Demography. 50(6): 2173-2181.


Figure 1Global Footprint Network, 2017.

Creative Commons Attribution 3.0 United States
This work is licensed under a Creative Commons Attribution 3.0 United States.