Arguably the most ambitious ecological theory based on self-organization is the Gaia hypothesis, which postulates that the biosphere itself evolves to a homeostatic state. Lovelock suggested the Daisyworld model as an illustration of how this process might occur. On the hypothetical Daisyworld, black and white daisies compete for space. Although both kinds of daisies grow best at the same temperature, black daisies absorb more heat than white daisies. When the Sun shines more brightly, heating the planet, white daisies spread, and the planet cools again. When the Sun dims, the black daisies spread, warming the planet. In this way, competitive interactions between daisies provide a homeostatic mechanism for the planet as a whole.
The idea behind Gaia is that ecosystems will survive and spread more effectively if they promote the abiotic conditions required for their own persistence. If so, ecosystems might gradually evolve to be increasingly robust, and if this happened on a global scale, then the biosphere itself might behave as a self-regulating system. However, evidence for Gaian processes in real ecosystems remains tenuous and their theoretical plausibility is disputed.
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