Daisyworld

James Lovelock and Andrew Watson[?] originally illustrated the Gaia theory with Daisyworld in a paper published in 1983. Daisyworld, a computer simulation, is a hypothetical world orbiting a sun whose temperature is slowly increasing in the simulation. The simulated planet is seeded with two different species of daisy as its only life form: black daisies and white daisies. White daisies have white flowers which reflect light very well and grows best in warm temperatures, and the other species has black flowers that absorb light well and grows best in cool temperatures.

At the beginning of the simulation, Daisyworld is so cold that only a few black daisies, and almost no white daises, can survive. Whenever the planet's temperature decreases, the black flowers tend to predominate, they absorb a little heat from the sun, which causes the planet's temperature to rise, allowing a greater proliferation of black daisies, more absorption of heat, and so on. As the planet becomes hotter white daisies begin to breed as well, and eventually the planet reaches a point of temperature equilibrium. Any increase in temperature is combated by a greater proportion of white daisies; any decrease leads to more black daisies. Such a system is remarkably stable against varying solar input; the entire planet maintains homeostasis. Eventually the external temperature becomes too hot for the daisies to oppose, and heat overwhelms the planet.

When the simulation is run without the daisies, the planet's temperature proceeds in lockstep with that of the sun. With the daisies, at the beginning of the simulation there is enhanced warming, and at the end of the simulation enhanced cooling, resulting in a close to equilibrium temperature for most of the simulation. In this way the daisies are modifying the climate to make conditions more hospitable for themselves.

Later extensions of the Daisyworld simulation included rabbits, foxes and other species. One of the more surprising findings of these simulations is that the larger the number of species, the greater the ameliorating effects on the entire planet. These findings lent support to the idea that biodiversity is valuable, and sparked the modern biodiversity debate[?].

A version of the Daisyworld simulation was included in the Maxis video game SimEarth[?].

See also :Gaia theory -- Gaia Hypothesis

External references and links

• Watson, A.J., and J.E. Lovelock, 1983, "Biological homeostasis of the global environment: the parable of Daisyworld", Tellus 35B, 286-289. (The original paper by Watson and Lovelock introducing the Daisyworld model.)
• A web-based implementation of the Daisyworld model (http://gingerbooth.com/courseware/pages/demos#daisy)