The destructive power of exponential growth

12 02 2007

I draw readers’ attention to a (fairly) new blog by the name Growth is Madness.  Establshed by Dr John Feeney PhD, a psychologist turned writer from the US, it provides a cogent argument for tackling population growth and economic growth as currently defined in developed economies.  Take a look.

On this topic I thought I would provide this extract on the subject of growth from a brilliant book by Australian physicist and author  Geoff Davies –Economia: New economic systems to empower people and support the living world. (Can purchase here)

…a simplified example will illustrate two inescapable lessons.  Suppose there is a small pond in which live 1000 algae (single-celled plant organisms).  Suppose the  pond can sustain 1 trillion algae (a million million): if there are more algae than this the pond’s ecology will be upset and algae will start to die.  Suppose these algae divide once every day while their supply of nutrient’s last.  On the second day there will be 2000 algae, still a trivial number of these tiny organisms.  On the third day there will be 4000 algae.  Question 1: how long will it take before there are 1 trillion algae?  Answer: thirty days.

….Suppose the algae in the pond are clever.  Suppose they realise they cannot keep breeding forever, so they agree they should do something before the pond gets full.  They agree that when the pond is half full, there will still be plenty of pond left but they should start discussing birth control.  Question 2: how much time do they have left when they reach half a trillion?  Answer: one day.  On the twenty-ninth day there will be half a million algae and on the 30th day there will be 1 trillion algae.

Human population has been increasing faster than exponentially during the historical period……The (unknown) person counted as the 6 billionth human alive was born in late 1999.  At that time, the 5 bilionth was not yet a teenager, the 4 billionth was just over thirty and the 2 bllionth was still under seventy.




One response

12 02 2007
John Feeney

Hey thanks for the nod, Verdurous. 🙂 Good post. Yeah, that algae story is a good one. It appears to be based on an old French riddle about lily pads covering a pond, only he’s improved upon it by showing how fast you can actually get up to astronomical numbers.

There is some debate about whether world population is still growing exponentially. I’ve seen even some people highly trained in mathematics arrive at differing conclusions. (The population growth rate slowed in recent times, but some experts say that’s not enough yet to make the growth something less than exponential.) But whatever the technical answer, it’s clear we’re still seeing a *lot* of growth.

Davies’s book looks good. I may have to put that one on my list.

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