Play the Population Growth and Crash game

coyote

Go here and click on the "Run Applet" button. Then select the "View Graph" tab and play with different Birth rates and Carrying capacities. Try changing the carrying capacity (a la Peak Oil) partway through the curve to simulate a dieoff -- even an extinction. I feel tremendously guilty... but it's kind of fun...
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TorrKing

Cool

Torjus Gaaren

Eddie_lomax

Novus · Light Sweet Crude Joined: Jun 21, 2005 Posts: 1750

To model PO start with a low carring capacity and a high birth rate. Then up the carring capacity to represent the discovery of oil. Then lower the carring capacity and drop the birth rate to less then 1.0.

Eddie_lomax

gego · Light Sweet Crude Joined: Mar 03, 2005 Posts: 1334

Compare the actual human population growth to this cool aplet, and then try to tell me that we are not in for a catastrophic dieoff whether or not you consider peak oil. Add in the concept of peak oil, and only denial will keep you from seeing the obvious future.

RonMN

Interesting. A birth rate of 3.9 went on & on but change it to 4.0 and it crashed in 26 generations.
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JustinFrankl · Intermediate Crude Joined: Aug 22, 2005 Posts: 657

Uh-oh.

So, looking at the posted graph, I tried to visually match the curve in the applet by playing with the numbers.

I let the applet run 60 generations with a carrying capacity of 2000 (for 2 billion people) and birth rate of 1.05, then I clicked on Stop. The population was 36.

To simulate the introduction of oil into our society, as it happened 5 generations ago, I increased the carrying capacity to 7000.

The next few generations, I used the Step button, the first time increasing the birth rate to 1.25, and then 0.25 thereafter. So I put in 1.25, Step, 1.5, Step, 1.75, etc. I made it up to 3.0, and the curve still resembles the population graph above (although I understand the year/generation scales don't match). The population stood at 6490 (6.49 billion people).

Then I kept the birth rate the same, at 3.0, and dropped the carrying capacity to 3500, to simulate the loss of oil.

Step.

And the population dropped to zero. Shocked

And, yet, I felt a guilty little pleasure. Embarassed

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coyote

JustinFrankl · Intermediate Crude Joined: Aug 22, 2005 Posts: 657

bobcousins

This applet shows something very interesting, but not what you think. The application of the model is way too simplistic, and real life is much more complicated and subtle. The logistic equation has chaotic behaviour.

Graph

(From Wikipedia)

With r below around 3, the curve is smooth and predictable. However, much above 3 the behaviour becomes chaotic. Before chaos theory was developed, ecologists would dismiss wildy varying populations as "abnormal", as they didn't fit the ideal of a approaching a harmonious equilibrum. In fact we now understand that wildly varying population level is a natural phenomenon, and some species even exploit it.

The fact the model goes to zero when you juggle with the parameters is quite meaningless. I think it is just an artefact of the way it was coded. It just demonstrates naive modelling ability. When people make simple predictions using a model where the fundamental behaviour is chaotic, you have to treat the predictions with a healthy degree of caution.

If you like to play around there is a fun applet here. If you want to delve into the math, look here!
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grabby · Light Sweet Crude Joined: Nov 08, 2005 Posts: 1328