W. von Bloh, A. Block, and H.-J. Schellnhuber
Tellus 49 B, 249-262 (1997)
Potsdam Institute for Climate Impact Research (PIK),
Telegrafenberg, P.O. Box 60 12 03, D-14412 Potsdam, Germany.
A two-dimensional extension of the simple Lovelock-Watson model for
geosphere-biosphere feedback is introduced and discussed. Our enriched
version also takes into account various pertinent physical, biological, and
civilisatory processes like lateral heat transport, species competition,
mutation, germination, and habitat fragmentation. The model is used as
a caricature of the Earth System, which allows
potential response mechanisms of the biosphere to environmental stress (as
generated, e.g., by global warming or anthropogenic land-cover change) to be investigated qualitatively.
Based on a cellular automaton representation of the system, extensive
calculations are performed. They reveal a number of remarkable and,
partially, counter-intuitive phenomena: our model biosphere is
able to control almost perfectly the geophysical conditions for its own
existence. If the environmental stress exceeds certain 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 and geometry of habitat fragmentation.
It turns out, in particular, that unrestricted Darwinian competition, which
reduces the number of co-existing species, is the best guarantee for survival
of the artificial ecosphere as a whole.
Full text as a HTML-document.