Daisyworld in 2D

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Daisyworld is an idea of Andrew J. Watson und James E. Lovelock (1983) and describes a hypothetical planet that is exposed to a sun of steadily increasing radiation, such that the planet's temperature would slowly increase with time. On the planet, only two species can live. Black and white daisies, which, due to their different albedo, regulate the mean temperature of the planet to a relatively constant value. The daisies can live between 5°C and 40°C, with an optimal growth rate at 22.5°C. Watson and Lovelock published this model to demonstrate the Gaia hypothesis, i.e., the regulation of environmental parameters and biota due to feedback mechanisms that lead to a condition of planetary homeostasis.
The model here is a 2-dimensional variant of the orginal 0-dimensional Watson and Lovelock model, based on the Stefan-Bolzmann law and heat diffusion coupled to a cellular automaton. Similar and more advanced simulations have been done before, e.g., by Werner von Bloh (http://www.pik-potsdam.de/~bloh/).