Thursday, March 27, 2008

St. Matthew Island reindeer

The following example is for me one of the most important to keep in mind when considering whether we should believe in the predictions of the scientists concerning the future evolution of our environment, or whether we should listen to the skeptics. I initially read it in 80 Hommes pour changer le monde, where Sylvain Darnil and Mathieu Le Roux quoted it from Paul Hawken's book, which is why I wanted to read this book in the first place.

"Natural and human history are full of examples in which animals or humans exceeded carrying capacity and went into steep declines, or extinction. A haunting and oft-cited case* of such an overshoot took place on St. Matthew Island in the Bering Sea in 1944 when 29 reindeer were imported. Specialists had calculated that the island could support 13 to 18 reindeer per square mile, or a total population of between 1,600 to 2,300 animals. By 1957, the population was 1,350; but by 1963, with no natural controls or predators, the population had exploded to 6,000. The original calculations had been correct; this number vastly exceeded carrying capacity and was soon decimated by disease and starvation. Such a drastic overshoot, however, did not lead to restabilization at a lower level, with the "extra" reindeer dying off. Instead, the entire habitat was so damaged by the overshoot that the number of reindeer fell drastically below the original carrying capacity, and by 1966 there were only 42 reindeer alive on St. Matthew Island. The difference between ruminants and ourselves is that the resources used by the reindeer were grasses, trees, and shrubs and they eventually return, whereas many of the resources we are exploiting will not."

* William R. Catton, Overshoot, The Ecological Basis of Revolutionary Change (Urbana and Chicago: University of Illinois Press, 1982, pp. 216-217).

Paul Hawken, The Ecology of Commerce. A Declaration of Sustainability.
(Chapter "The death of birth").


François Ascani said...

An example closer to home that, I think, I have learnt a long time ago in a TV doc: Rabbit Island. Rabbits were introduced on the island and destroyed it. The damages are still visible: no trees, no bushes and eroded.

Davy said...

It reminds me the lokta-volterra equations that rule the population of preys and predators (a quick google or wikipedia will tell you more)

And also l'ile de paques (see EDF ads telling how the people of the island died right after having cut all the tree, just to raise their stone gods...)