Wednesday, 15 August 2012

Human Population Dynamics on a Finite Earth....

Growing human population with its habit of over consumption on a planet with finite space and resources provides some fascinating scenarios.   Population quadrupled in the 20th century.  The momentum of population growth will almost certainly take us from 7 billion in 2011 to over 9 billion by 2050. 
Where do we go from there?  the situation is serious enough that I shall deliberately make some provocative statements to start a serious debate.  We need to look at the big picture and come out of the habit of theoretically solving a local limited problem and announce that as a solution to everything.

In examples  1 and 2  we set out the nature of exponential growth.  Example 2 is directly applicable to human population on earth for which the doubling period is not one week (as it was in example 2) but somewhat longer - 50 years in the 20th century and may be of the order 100 years in the 21st century.  The increase in doubling period might partly be a result of humans hitting the earth's resource ceiling although many experts think that we reproduce less as we grow richer and doubling in numbers takes longer.  Some even feel that if we all got much richer then population will start decreasing.  Let me explain the problem with this line of thinking:

On average, about a quarter of us are living very well - are rich.  One third of us (China and India with a combined population of 2.5 billion) would like to increase consumption seriously to reach at least the European levels.  The remainder live at or below subsistence levels.  Currently we use resources in excess (1.5 times) of what is considered sustainable.  To raise every body's standard of living to European level will require resources of 4 Earths; to reach US levels will require 15 Earths.  And we are talking about 7 billion population.  Consumption by 9 billion rich humans will be correspondingly greater.

Look at it another way:  To support US style living for everybody on earth, we need to reduce our numbers by a factor of 15 - the population can only be about 500 million.  The reproduction rate will be no problem according to experts when we are all rich but how do we reduce the population to 500 million.  Please send me an e-mail ( if you think I have missed something here.
The conclusion I draw is that we have already hit the resource ceiling and increase/decrease in human population will now be governed by the resource limits of our ecosystem. 
It is not possible for our visionary world leaders to make the 7 billions of us rich quickly.

Some say that science and technology will solve the resource problems.  NanoTechnology (NT) will produce limitless food without waste, will be nonpolluting, even clean up past pollution, etc. etc...  
NT will also improve medical care, may be even allow people to live for ever (much longer than 100 years would not be unreasonable); thus decreasing the death rate drastically.  Population growth is the difference of birth rate minus the death rate.  For stable population birth rate must be zero if nobody dies.  Imagine a world full of 100 year old rich people.  Who will do the work?  Robots probably?  But then will these robots no get fed up with humans and decide to do something about it - after all they will think logically!  Now this is the subject of my blogs in 2013. 
Let us go back to human population scenarios:

The reason I think zero or negative population growth is not possible is the way exponential growth works.  This was explained in example 2.  We looked at doubling steps.  Even if 99% of the population dies the remaining 1% will grow back to original numbers within 7 doubling steps - 350 years in the case of humans.  What this means is that if a natural or human generated catastrophe eliminates 99% of the population - it will be 7 billion again in 350 years.

Nations of the world do not all think the same way.  Population, largely poor, in African and South American (A&SA) countries is doubling in 25 years or less.  Rest of the world might stabilise its population but in 100 years, A&SA will have increased their population by a factor of 16.  India's population is projected to reach 1.6 billion in 2050 from 1,2 billion now.   Indigenous US population is not expected to grow but to do the work they will allow 100 million new immigrants over the next 40 years who will demand US style standard of living.  Effectively US population will grow by more than 25% over the next 40 yaers. European population trends will not be much different from US - I believe.  It seems clear to me that eventhough local population in rich countries does not grow by itself, new immigrants will boost the population - and the arguments about reproduction rates decreasing with prosperity do not hold out - unfortunately.

So where do we go from here - if global population continues to incrase with a doubling period of 100 years then in 1000 years (10 doubling periods) the population will hit a number of 7000 billions.
what it means in terms of space and resources is quite obvious.  As I had said previously - it won't happen.

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