A Short Lesson In Exponential Growth

A wallaby got into the garden last night, and demolished my newly planted sweet potato patch. I spent my whole mowing session this morning devising recipes for wallaby – Turkish wallaby stew, marinated baked wallaby, wallaby kebabs….

I checked the fortress fence for holes, but I think it got in across the verandah through the house and into the garden! It’s not as if it is very hungry – after the recent rains I have trouble keeping up with the mowing – it just likes sweet potatoes better.

I didn’t catch the wallaby, but I caught the turkey pictured red handed (or red headed) in the bananas right outside my bedroom window this morning.

After 25 years of protecting and cultivating the wildlife, we have wildlife. We have wallabies and paddymelons, bandicoots and bush turkeys, possums and flying foxes, bower birds and king parrots. We have goannas and carpet snakes and quolls and very cute microbats and even a new generation of wedge tailed eagles. It took a long time for populations to come back from the verge of local extinction. But then, all of a sudden I got a lesson in exponential growth.

For nearly fifteen years, wildlife populations had been growing each year from very very rare to very rare to rare and my big unfenced garden was of no interest. 2, 4, 8. Then all of a sudden, doubling meant going from half capacity and plenty of resources, to over capacity and willing to try unfamiliar foods in dangerous places. 4000, 8000, 16000.

And since then there’s been no stopping them. My big open garden was redeveloped as a much smaller, fortress fenced, very intensive system, with as much attention to getting value from the vertical space as the ground. Ironically, my garden could now fit into a suburban block!

It has made me change my gardening style – more about up-gardening on the Garden page – but it has also made me very aware of just how very sudden a change exponential growth can bring on, and how counter-intuitive it is.  I think the famous quote from Dr. Albert Bartlett – “The greatest shortcoming of the human race is our inability to understand the exponential function”  might be our epitaph.