Jasper Creegan

October 2007

Complex Dynamic Systems

A Summary of the Daisyworld Model

Daisyworld is a model that supports the Gaia Theory. James Lovelock is the originator of the Gaia theory and when his theory was first presented to the math and science world, many refuted his claims that all the organisms that make up the biosphere are able to cooperate in maintaining the surface environment of the earth. Lovelock realized the need for some sort of evidence to support his theory that could be easily comprehended by his critics. He worked with Andrew Watson to create the Daisyworld model.

Daisyworld clearly gives evidence to Lovelock's theory but it is a vastly simplified model because it is impossible to take into account the countless variables that affect the earth's biosphere. Daisyworld is made up of only two organisms, white and black daisies. However, the model makes assumptions such as, the rain is consistent and only occurring in the night, which in turn makes all the days cloudless. The greenhouse of the model's planet is also kept constant. The main aspect of the Daisyworld model is that the white and black daisies have different albedos meaning, the black daisies absorb more light making from the sun, raising the temperature, and the white daises reflect more light from the sun, cooling the temperature.

A series of equations give allow the model to calculate the temperature. The variables that need to be taken into account are the energy emitted, the energy absorbed, the energy reflected, the energy received, the solar luminosity (the solar luminosity of the Daisyworld model begins at 550 w/m2 which is quite low because all suns begins with a diminished luminosity and through its stages gets up to 1650 w/m2) and the overall albedo of the model at each stage.

The albedo of the Daisyworld model is calculated through a function of how much land is covered by black and white daisies. Land with no daisy covering it has a set albedo of .5, white daisies have a set albedo of .75 and black daisies have a set albedo of .25.

However, one thing that must be added into the makeup of the Daisyworld model is the growth rate for the white and black daisies, or else there would be no way to tell which color would grow at what temperature. Although the white daisies lower the temperature, they thrive when the temperature is higher and when it gets too cool they die off. The black daisies however, thrive when the temperature is cooler but when it gets too hot they die off. This may seem contradictory but if the variables are set correctly, it works in harmony. For example, there may be a large patch of black daises which will be absorbing much of the energy but this cannot last for so long because the temperature in that area will get too high for the black daises and as they die off the white daises thrive in this hot region and vice versa.

Although Lovelock's Daisyworld model is an immensely simplified example of the earth's biosphere, it gives evidence to his Gaia theory. Daisyworld takes two organisms, the black and white daisies, and one climactic factor, temperature to convey how organisms regulate and are regulated by the climate. The model doesn't take into account all the variables and organisms and climactic factors in our earth's biosphere but this is truly impossible. The few variables presented in the Daisyworld model can be adjusted by the user and one can being to understand Lovelock's Gaia theory and the claim that the earth is a self-regulating system including living and non-living parts.