Interspecific competition affects temperature stability in Daisyworld

The model of Daisyworld showed that nonteleological mechanistic responses of life to thephysical environment can stabilize an exogenously perturbed environment. In the model, 2species of daisies, black and white, stabilize the global temperature of a planet exposed todifferent levels of insolation. In both species, the response of the growth rate to local temperatureis 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 suitablefor life. Watson and Lovelock made the stronger claim that ‘‘the model always shows greaterstability with daisies than it does without them.’’ We examined this claim by introducing anextra source of competition into the equations that describe the interactions between the daisyspecies. Depending on the parameters of competition, temperatures can vary more widely withincreasing insolation in the presence of daisies than without them. It now seems possible, timelyand perhaps necessary, to include an accurate representation of interspecific competition whentaking account of vegetational influences on climate.