Daisyworld - Modifications To The Original Simulation

Modifications To The Original Simulation

Later extensions of the Daisyworld simulation which included rabbits, foxes and other species, led to a surprising finding that the larger the number of species, the greater the improving effects on the entire planet (i.e., the temperature regulation was improved). It also showed that the system was robust and stable even when perturbed. Daisyworld simulations where environmental changes were stable gradually became less diverse over time; in contrast gentle perturbations led to bursts of species richness. These findings lent support to the idea that biodiversity is valuable.

Daisyworld was designed to refute the idea that there was anything inherently mystical about the Gaia hypothesis that Earth's surface displays homeostatic and homeorhetic properties similar to those of a living organism. Specifically, thermoregulation was addressed. The Gaia hypothesis had attracted a substantial amount of criticism from scientists such as Richard Dawkins, who argued that planet-level thermoregulation was impossible without planetary natural selection, which might involve evidence of dead planets that did not thermoregulate. Dr. W. Ford Doolittle rejected the notion of planetary regulation because it seemed to require a "secret consensus" among organisms, thus some sort of inexplicable purpose on a planetary scale. Both neoDarwinians discarded the large body of evidence for planetary regulation based on absence of a mechanism to account for it. Lovelock's model countered such criticism by showing how regulation arises naturally from the assumption of growth within a temperature range. None conscious purpose but natural selection only is required to account for the thermoregulation of Daisyworld.

Later criticism of Daisyworld itself centers around the fact that although it is often used as an analogy for Earth, the original simulations leaves out many important details of the true Earth system. For example, the system requires an ad-hoc death rate (γ) to sustain homeostasis, and it does not take into account the difference between species-level phenomena and individual level phenomena. Detractors of the simulation believed inclusion of these details would cause it to become unstable, and therefore, false. Many of these issues are addressed in a more recent paper by Timothy Lenton and James Lovelock in 2001. In this paper it is shown that inclusion of these factors actually improves Daisyworld's ability to regulate its climate.