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Population reduction - a calculation
GDP growth remains the main paradigm of the speakers of Business, whereas population growth remains a taboo.
The following is a trial to calculate the world population size if from now on women would have zero or one single child.
The premise of the exercise is the notion that the world is overpopulated far beyond it s carrying capacity.

How Badly Overpopulated Will We Be In 40 Years? back


Unless earth is hit by a massive meteor, we will be vastly overpopulated for well over 40 years even if everyone is immediately sterilized. This means we will experience a die-off and more species extinctions. I suggest that earth's sustainable population is only 2,500,000 (1).

Yes, that's million, not billion. If you think that is extremely low, think again. That is over 7 times the current population of all great apes (chimpanzees, bonobos, gorillas, and orangutans) combined! That is 10 times earth's population that persisted for the majority of our 2 million year human history! Perhaps if you think 2.5 million is too low for a global sustainable human population you are underestimating:

A) the scale to which we convert land into food using non-renewable fossil fuels
B) how much we've already permanently degraded earth's carrying capacity
C) how unsustainable our current "6th Mass Extinction" is

My estimate of 2.5 million as a sustainable global population is based on a viable hunter-gatherer population 10,000 years ago (when our numbers forced us into the low EROEI lifestyle of agriculture) of 5 million. I adjusted 5 million to 2.5 million because I believe our carrying capacity has been permanently degraded by at least 50%. There aren't as many species left and much of our land is now polluted, deforested, paved, infertile, etc. I think it is important to have a low enough population that a high EROEI hunter-gatherer culture is viable for all who desire it.

How badly we are overpopulated in the next 40 years depends on what we do. Quinacrine sterilization has great potential and offers real hope for a brighter future. (2) Without harming anyone we can ensure maximum speed of population decline (which we already know is slower than desired) using Quinacrine sterilization which would have to be mutually-agreed upon by the majority and enforced just like other laws (eg: everyone has to pay taxes).

Assuming average life expectancy is 80 and equal age and sex distribution...

What is a population estimate in 40 years if all females from now on have 0 children during their reproductive lives?

Current population is 6.7 billion.

If nobody reproduced for the next 40 years, our population would be 3.35 billion because half would have exceeded life expectancy.

What is a population estimate in 40 years if all females from now on have 1 child during their reproductive lives?

Average age for menopause is 51 years (3,4).

Average age for menstruation is 13 years (5).

One Peruvian female gave birth at age 5 and one Indian female gave birth at age 70. (6,7)

Biologically, the theoretical range of fertility is 65 years but the practical range of fertility is more like 38 years.

51 + 13 = 64

64 / 2 = 32 (average age of fertile female)

We will assume that the average age that each woman has her one child is 32 (generation time).

How many already existing females will be of child-bearing age within the next 40 years?

51/80 = 63.75% of 3.35 billion = 2.135625 billion

How many already existing women are already of child-bearing age?

38/80 = 47.5% of 3.35 billion = 1.59125 billion

How many already existing females are not yet of child-bearing age?

13/80 = 16.25% of 3.35 billion = 0.544375 billion

How many of these 1.59125 billion women have already had one or more children?

Let's assume 80% worldwide. (Based on footnote C)

Therefore, 20% of 1.59125 billion = 0.31825 billion women of child-bearing age who already exist but have not yet had their one child. They already average 32 years so will have their child within 1 year.

0.544375 billion more females will each be having one child. These females are from age 1 to 13 averaging 7 years today and will reach 32 years in 25 years when they give birth. 32 years later, or 57 years from today, their female offspring will add another 0.544375 billion / 2 = 0.2721875 billion babies to the earth.

0.31825 billion + 0.544375 billion = 0.862625 billion children born by women who are alive today

0.31825 billion babies were born within a year of today so half of them (the 0.159125 billion females) will each have one child in 32 years. These 0.159125 billion babies are the grandchildren of the 0.31825 billion females averaging 32 years today.

Of the 0.544375 billion babies born 25 years from today by the females who average 7 years today, 0.2721875 billion are female babies but these babies will not quite have their babies within the next 40 years. Their babies will be born 57 years from today.

Since the elder 50% of the population will be dead within 40 years...

3.35 billion + 0.862625 billion + 0.159125 billion = 4.37175 billion people

Therefore, if all females from now on have a total of 1 child during their reproductive lives, the earth's population would decline from 6.7 billion to 4.37175 billion.

The difference between choosing 1 child per female instead of 0 child per female amounts to over 1 billion additional consumers over 40 years.

I think the choice is clear. 0 child per female law is the only sane course of action to take over the next 40 years.

Since 3.35 billion and 4.37 billion are both over 1000 times a sustainable world population, I am in favour of no new babies for the next 40 years.


Brishen Hoff
President of Biodiversity First

1) http://ecologicalcrash.blogspot.com/2008/11/how-to-live-in-sustainable-world.html
2) http://home.alltel.net/bsundquist1/qs.html
3) http://www.peelregion.ca/health/hsexual/htmfiles/masmeno.htm
4) http://en.wikipedia.org/wiki/Menopause
5) http://en.wikipedia.org/wiki/Menarche
6) http://en.wikipedia.org/wiki/List_of_youngest_birth_mothers
7) http://en.wikipedia.org/wiki/List_of_oldest_birth_mothers


A) http://www.msnbc.msn.com/id/17937795/
"Frieda Birnbaum, the 60-year-old New Jersey woman who gave birth to twins in May."

B) http://www.thesun.co.uk/sol/homepage/woman/real_life/article64716.ece
"We chose to never have kids
By CANDICE GIFFORD Published: 26 Sep 2006

NICKI DEFAGO and husband Jim Scobie were on an extended honeymoon in Central America when they decided never to have children.
Watching the sun set on the Mayan ruins of Mexico’s Chichen Itza, they realised that if they became parents they would not have the time or money to pursue that kind of lifestyle.
It is a controversial choice and the couple have had to fight a lot of prejudice over it.
Nicki, a 40-year-old journalist, says: “Having made my decision, I noticed there were hundreds of books on having a baby but nothing out there saying having children is not for everyone.

“That’s why I decided to write a book (Child Free And Loving It! by Nicki Defago, Vision Paperbacks, £10.99) about the pleasures of child-free living.

“People are constantly telling me I’m being selfish or that I will change my mind. Some people say, ?But that’s what women are for.’

“A man at a party once told me I was abnormal. I pointed out that a lot of men don’t have children. He said, “Yes, but men can do other things.” As if women can’t!"

C) http://www.iht.com/articles/2008/08/19/america/fertility.php www.nytimes.com/2008/08/19/us/19census.html "Twenty percent of American women from the ages of 40 to 44 have no children"

D) http://www.washingtonpost.com/wp-dyn/content/article/2006/11/24/AR2006112400986.html "6.6 percent of women in 1995 declared themselves voluntarily childless" Posted by Brishen Hoff at 3:59 PM

bakakarasu said... Nicely done, and the math work is impressive ;-)
As your authors note, we’ve already exceeded global carrying capacity. We are now in “overshoot”. (Visualize a car sailing smoothly, but quite temporarily, through the air after having been driven off of a cliff.)

Global population is nearing 7 billion. Different theorists using different methods seem to end up agreeing that global carrying capacity is probably about 2 billion. (This assumes some level of social justice and a moderate, low by US standards, standard of living. More is possible if you accept a cattle car / Matrix-esque "life".) The authors here arrive at a much lower number.

In any case, we will get to that much-lower-than-7-billion number the hard way (wars, famine, disease, and their accompanying losses of environmental quality, freedom, and social justice) OR the less hard way (immediately and drastically reducing our population voluntarily). Yes, all of us, yes, everywhere. There is no scenario anywhere in which population growth is a "good thing" long term.

Yes a drop in population would cause problems, but none of those problems are as big as the problems, suffering, and environmental collapse that is certain to occur if we don’t.

I disagree with any argument that there is some “right to reproduce”. If there is any "right to reproduce" it's in the concept that one has the freedom to nurture a child or children and form some sort of family. Biological reproduction is not necessary to do that and there are many in need of this sort of nurturing.

This is a global issue with local and nation-state consequences. For example, immigration is a consequence of overpopulation, not a cause of it. Likewise, global climate change is not impressed by national boundaries.

No technological / "alternative energy" options have the capacity or can be ramped up fast enough to avoid major global calamity. That isn't to say we shouldn't do them. Aggressively shifting to alternative energy is necessary, just not sufficient.

For more comprehensive analysis of all this I suggest
Approaching the Limits (www.paulchefurka.ca)

Bruce Sundquist on environmental impact of overpopulation (http://home.alltel.net/bsundquist1/)

The Oil Drum Peak Oil Overview - June 2007 (www.theoildrum.com/node/2693)

Bandura etc. (http://growthmadness.org/2008/02/18/impeding-ecological-sustainability-through-selective-moral-disengagement/)

Albert Bartlett on the exponential function as it relates to population and oil: (http://c-realm.blogspot.com/2008/12/kmo-interview-with-albert-bartlett.html)

...and of course the classic "Overshoot" by Catton

January 23, 2009 11:02 PM Tim Murray said...

Bakakarasu’s comment was incisive except for one passage, which is fundamentally in error, despite the agreement it receives in mainstream thinking:

”This is a global issue with local and nation-state consequences. For example, immigration is a consequence of overpopulation, not a cause of it. Likewise, global climate change is not impressed by national boundaries.”

1. “Immigration is a consequence of overpopulation, not a cause of it.” On the contrary, there is a dialectical relationship between the two. Affluent nations such as Canada offer a safety valve for overpopulated countries to dump their excess numbers, thereby providing no incentive for them to come to terms with their overshoot. And an exodus of dissidents removes critical political pressure from the corrupt dictatorships which preside over this population growth. Their overthrow is a precondition in most cases for any meaningful family planning initiatives to take place. Mugabe is a case in point. He more or less told CIDA and the Canadian government to mind its own business, and his reaction has been typical of many, like the great “Malawi” of a neighbouring state. In turn, foreign aid is often a response to the powerful lobbies of immigrant and ethnic colonies within affluent countries rather than to the scale of distress in the receiving nation. Can anyone tell me why Israel consistently receives up to $10 billion a year from the United States? Multicultural-schism has badly distorted the foreign policy of Canada as well. There are at least 30 ‘swing’ ridings where foreign-born voters can and have punished political parties and MPs for not making their homelands a priority in the dispensation of aid. Aid that is not made conditional on birth control or the democratic restructuring of the recipient countries so necessary for an effective population plan. Consequently, Canada’s foreign aid can be characterized as external “baby bonuses” that contribute decisively to the “push” factors that propel migrants to our land.
2. “Climate change is not impressed by national boundaries”. Assuming the veracity of anthropocentric global warming (AGW), a study released by CIS in August of 2008 clearly established that, for example, immigrants who arrive in the United States quadruple their GHG emissions. It is vitally important that industrialized countries, and most especially the US, Canada and Australia, close their borders as an effective counter to GLOBAL climate change. Injecting new foreign consumers into the third fastest growing nation on the planet---the US---which at the same time consumes at least a quarter of global resources, accelerates the timetable for our GLOBAL demise. More important, however, is the fact that climate change is not or should not be the primary focus for environmental concern. The loss of biodiversity services, also a result of human overpopulation, is a more imminently lethal threat than AGW. Human accommodation to climate change could cost us perhaps up to 90 or 95% of the world’s population, if some scenarios are to be believed. But homo-sapiens cannot survive without the $33 trillion in free services provided to us by healthy biodiversity. Biodiversity can and has flourished in local or national environments despite obliteration in neighbouring regions. Notwithstanding its global atmospheric impact, the clear-cutting of a Central American rainforest and the resultant loss of wildlife there does not mean the end of Canada’s Great Spirit Bear population or any other non-avian species native to our area. We can happily address our own folly in Canada and the economic forces propelled by immigrant-driven growth without wringing our hands over foreign ecological devastation. The environment is both ‘singular’ and ‘plural’. Preservation of regional habitat is not contingent on the willingness of other jurisdictions to do the same. ‘Holding our breath’ until overpopulation is tackled globally is a fool’s pastime. As Garrett Hardin said, overpopulation begins at home, and global population stability and reduction can only be the sum total of local victories, here and abroad. So yes, while the atmosphere is a global canopy oblivious to political or bioregional boundaries, it does not mean that nations like Canada should be cavalier about immigration, or await global cooperation to attack environmental problems that are wrongly perceived as purely global.

In short, “getting our own house in order” and locking our candy store to those who would sweep down upon us like locusts to pick our environment clean is essential not only to our ecological survival, but ultimately to the survival of the countries of emigration. The vast sums of money wasted on the settlement of immigrants, not to mention “multicultural” integration (or is it ‘disintegration’ services?) could instead be deployed in foreign aid tied to family planning to relieve the force that is pushing migrants out. For Canada, that ‘waste’ of annual billions (according to the Grubel report of 2002) could make a decisive difference in leveraging population stability and reduction in selected undeveloped countries. Global overpopulation and immigration are two sides of the same coin. It is definitely not a ‘cause and effect’ relationship.

Tim Murray, January 24/09

January 24, 2009 8:19 PM
Suds said...
The original article (by Brishen Hoff) is useful perspective but is it not more of a thought experiment than a vision of reality?

A global consensus on controlling 'right to reproduce' appears inconceivable in the near future. Humans don't have the capacity to achieve that, either emotionally or intellectually. So we need to ask what is achievable, beyond letting events take their course to the detriment of the human condition.

One possibility might be a change in attitudes towards the family. The declining population in some countries (Japan and England, for example, or so I understand) offers a glimmer of hope. Government incentives are possible that persuade families to reduce numbers of babies. Incentives are in place now, including the U.S., although the incentives in U.S. seem to favor more babies rather than fewer.

If family planning restrictions and archaic attitudes can be deposed, additional hope is offered.

The situation appears grim, but the bottom line is that, one way or another, a different view of humans on earth is inevitable in the next 40 years. Most would prefer changed attitudes that raise hope for success and reduce the possibility of chaos and grief. We need different ways of thinking about humans on earth.

January 28, 2009 11:36 AM
On a finite planet economic and population growth are suicide for humanity!
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