Interspecific competition affects temperature stability in Daisyworld

The model of Daisyworld showed that nonteleological mechanistic responses of life to the physical environment can stabilize an exogenously perturbed environment. In the model, 2 species of daisies, black and white, stabilize the global temperature of a planet exposed to different levels of insolation. In both species, the response of the growth rate to local temperature is identical, but differences in albedo between the 2 species generate differences in local temperatures. The shifting balance between the daisies keeps the global temperature in a range suitable for life. Watson and Lovelock made the stronger claim that “the model always shows greater stability with daisies than it does without them.” We examined this claim by introducing an extra source of competition into the equations that describe the interactions between the daisy species. Depending on the parameters of competition, temperatures can vary more widely with increasing insolation in the presence of daisies than without them. It now seems possible, timely and perhaps necessary, to include an accurate representation of interspecific competition when taking account of vegetational influences on climate.