Conclusion

  Our main objective has been the construction of a two-dimensional conceptual model for geosphere-biosphere-anthroposphere interaction, which is based on the Lovelock-Watson approach. Our model could be seen as being mid-way between pure toy models and three-dimensional analogical Earth-System models based on state-of-the-art and geographically explicit simulation modules for the atmosphere, the ocean, the biogeochemical cycles, civilisatory land-use etc. .

For the sake of computational simplicity, we have designed our extended Daisyworld as an cellular automaton, but this technical option does not affect the validity of our results.

Our system turns out to be rich in exhibiting a number of remarkable phenomena. In particular, we find that spatial heat transport and mutation even improve the self-regulation abilities of the model biosphere. As a matter of fact, in the limit of infinite system size, a first-order phase transition from optimum ambient conditions to a non-habitable environment will take place. The existence of a phase transition implies accompanying hysteretic effects, i.e., points of no return.

Fragmentation of potential growth space has a significant influence on the homeostatic performance of the biosphere. A unique threshold can be identified, where the regulation of global temperature becomes inhibited due to habitat disconnection. We also find that an unrestricted Darwinian selection of species under deteriorating environmental conditions warrants the subsistence of the biosphere as a whole. Biodiversity benefits from fragmentation, yet reduces the overall ecological performance of Daisyworld.

We plan to further pursue our simple geophysiological approach to Earth-system analysis by incorporating additional elements into our model. The next steps will be to include caricatures of the hydrological and biogeochemical cycles. Another interesting option is to simulate civilisatory habitat fragmentation by more realistic processes for urbanization and infrastructure expansion.