SELF-STABILIZATION OF THE BIOSPHERE UNDER GLOBAL CHANGE - A TUTORIAL GEOPHYSIOLOGICAL APPROACH

A 2-dimensional extension of the simple Lovelock-Watson model for geos phere-biosphere feedback is introduced and discussed. Our enriched ver sion also takes into account various pertinent physical, biological, a nd civilisatory processes like lateral heat transport, species competi tion, mutation, germination, and habitat fragmentation. The model is u sed as a caricature of the Earth System, which allows potential respon se mechanisms of the biosphere to environmental stress (as generated, e.g., by global warming or anthropogenic land-cover change) to be inve stigated qualitatively. Based on a cellular automaton representation o f the system, extensive calculations are performed. They reveal a numb er of remarkable and, partially, counter-intuitive phenomena: our mode l biosphere is able to control almost perfectly the geophysical condit ions for its own existence. If the environmental stress exceeds certai n thresholds, however, life breaks down on the artificial planet via a first-order phase transition, i.e., in a non-reversible way. There is a close connection between self-stabilizing capacity, biodiversity an d geometry of habitat fragmentation. It turns out, in particular, that unrestricted Darwinian competition, which reduces the number of co-ex isting species, is the best guarantee for survival of the artificial e cosphere as a whole.