Modeling Earth System Complexity: Theoretical Biology Approaches to the Gaia Hypothesis by Sergio Rubin

In this thesis three theoretical biological models of a living unity are implemented to study the dynamic organization and complexity of the Earth system from the point of view of the Gaia hypothesis–the Earth instantiates life at the planetary scale–. The first one is based on Chemical Organization Theory and the Zero Deficiency Theorem that is applied to Earth's biotic and abiotic reaction networks. This shows that at molecular level there are Earth’s reaction networks that are able to self-produce, i.e. to make autopoiesis, a key organizational feature of living systems. The second one is based on the Free Energy Principle–here active inference, shows that a biosphere-climate dynamical system model can remain at non-equilibrium steady-state climate dynamics by active inference of net incoming solar radiation. Finally, considering that Earth system components and operational processes satisfies the formal entailments of the (M,R)-system would mean that its complexity has a formal equivalence to a self-referential (impredicative) system, which cannot, in principle, be completely surrogated by an algorithmic representation. Yet, it may indicate that potentially the Earth components could have multiple functions and that the dynamics of the Earth could be context dependent with respect to its spatial environment. These three approaches of theoretical biology applied to the study of the Earth’s complexity opens up the plausibility that habitability, i.e. climate homeorhesis has occurred by self-fabrication and active inference at the planetary level and that the Earth complexity is akin to the complexity of any living system, which must be borne in mind in future Earth's climate modelling.