One of these was Paul Erdös who was the twentieth century’s most prolific mathematician, with 1475 papers to his credit. He rivals Leonhard Euler, the Swiss genius of the eighteenth century. There is a worthwhile biography of Erdös called ‘The Man Who Loved Only Numbers’, by Paul Hoffman (1998).
On a recent thread at this blog (Wise Men Excluded from Bushfire Royal Commission), I raised the issue of fuel connectivity, and suggested that it helped to explain the uncontrollable spread of bushfires over large areas of Victoria a few months ago.
The tonnage of available fuel determines the intensity, and convection column strength, and the number of flying embers, but connectivity determines ground spread. Wind is important, but large fires, of course, create their own wind. It seems to me that the application of Occam’s Razor makes climate superfluous to the argument, beyond there being weather dry enough for a fire to burn. Given dry fuel, fierce fires can occur even at mild temperatures. Surely we have all lit a pot-belly stove on a winter’s day.
Although I doubt if he had ever seen a bushfire, or a gumtree, Erdös had useful ideas on connectivity in networks. With a Hungarian colleague, he published papers about ‘giant patches’. These form when random connections are made between a set of random points (Erdös and Renyi 1959, 1960).
The idea of networks (connected graphs) originated, in Europe at any rate, with Euler, when he solved the puzzle of the seven Bridges of Königsberg. Recent applications have been in neural networks in the brain, disease epidemics, and the growth of the world wide web. ‘Six degrees of separation’ may ring a bell for some.
With regard to bushfire, as fire is excluded from a large area, formerly disconnected fuel patches join up, and this process suddenly accelerates as ‘cliques’ of patches start connecting. Some have called this phenomenon a ‘connectivity avalanche’. Once a certain threshold is passed, bushfire can spread uncontrollably. Ember showers, due to heavy fuel burning, can obviously accelerate the process by causing another level of connectivity.
I give this information for those constructive contributors who are interested in ideas about bushfire management. Probably I should publish it quickly before someone from academia claims it. Those involved in research will know the sequence: a) Rubbish, b) Well, perhaps in some cases, c) Of course, and I thought of it first.
Fuel reduction burning reduces both fuel quantity, and, importantly, connectivity. The restoration of something like Aboriginal patch burning, by both reducing fuel, and disrupting connectivity, would make large bushfires a thing of the past, no matter what the weather. The bush would be healthier, and safer for native animals, not to mention humans. Should I mention erosion and water supplies? Or the fact that mild fires sequester enormous amounts of carbon as charcoal, but very hot fires create mainly ash, and volatilize much of the nutrients?
David Ward lives in Western Australia and comments at this blog under the alias ‘Green Davey’.
The picture is of grass trees at Scott River, Western Australia, taken in January 2007, following a “mild, patchy burn”.
Previous contributions from Mr Ward include:
Nyoongars, Noolbengers and No Fires
Parachutes & Prescribed Burning
Noongars Knew Best (Part 2)
Noongars Knew Best