The surface of the ``naked'' planet, i.e., the planet without
vegetation, is characterized by an overall albedo .
The equilibrium temperature depends on the insolation S and the
black body radiation according to
where is the Stephan-Boltzmann constant.
The biosphere consists of two components only:
This feedback system has been analysed by several authors [12, 13, 14, 15] in great detail. One remarkable result is that, in contrast to the uncovered planet, the ``bioplanet'' is able to hold the global temperature relatively constant when the external ``control parameter'' S is varied within a rather wide range. This property of self-regulation is referred to as ``homeostasis''. As a matter of fact, homeostasis is achieved here by a rather simple mechanism: white (black) daisies are fitter in hot (cold) climates as their comparatively high (low) albedo tends to reduce (increase) the local temperature.
Note that by conceiving as a function of the concentration of the atmosphere, it is possible to take the greenhouse effect into account.