Spatial Daisyworld Model - Jamie Wood
The daisyworld model has a short and slightly controversial history, being intimately connected with Gaia Theory. Here we take the system on its merits and attempt in clude all the possible effects reported thus far in the literature.
There has been numerous articles written on Daisyworld over the years, so if the reader is interested in a general background I would suggest reading something written by someone more articulate than I. Typical examples may be found here, here or here, but this is far from exhaustive.
In summary the daisyworld parable consists of a model planet that orbits some distance from an imaginary sun, but is nonetheless similiar to our own. We model this world in an incredably simplified way, firstly we assume that the living things on this planet consists of daisies which appear in one of two types - white or black. If a space on the planet is not populated by on of these endemic species it will be bare. The daisies (often called biota) will grow according to prescribed (replicator) growth equations and both types distribute their "seed" perfectly. The planetary dynamics are simplified by assuming that the total amount of heat absorbed by this world is only a function of the average colour or albedo (white has albedo greater than one half, black has albedo less than one half). White daisies reflect more of the suns energy back into space, black daisies absorb more. The planetary temperature is supposed to equilibriate fast so that it is in balance and that the different patches of coloured daisies transfer heat between each other. The model has no spatial component in its original guise.
This model then exhibits the property of homeostasis or regulation as predicted by the Gaia hypothesis. More specifically the relative proportions of the black and white daisies adjust so that the overall planetary temperature is maintained at the optimal for growth.
The simplifications in the model are extreme, and many convincing arguments have leveled against it. To date however, the model survives intact and criticisms against it have failed to stick. Indeed most generalisations of model have continued to preserve the central property of homeostasis, despite even increasing complexity. The model we introduce below is no exception.
A model with two kinds of evolution
Bak, P. and Tang, C. (1989)
Earthquakes as a self-organized critical phenomena
The original BT slider block model.