Cascading Transitions in Coupled Complex Ecosystems.

The Earth system is arguably one of the most complex systems in the known universe. Over 4.5 billion years it has self-organised into a state which features complex differentiated life that covers its surface and penetrates its crust. This widespread biosphere requires stability in the sense of maintenance of temperature and pressures on the surface that allow liquid water. Within this range there is significant scope for change, some of it dramatic. Glaciation to inter-glacial cycles are classic examples of planetary-scale transitions. This paper examines the role of biological feedback on planetary-scale transitions. We present a conceptual model in which stability emerges as a consequence of interactions between environment and life. These mechanisms not only lead to stable ecosystem configurations, but can also produce critical transitions which we characterise as cascading transitions. Such failures can interact and produce system-wide transitions. Our results would be of interest to those studying real-world ecosystems, tipping elements in the Earth system as well as theoretical studies on complex artificial life systems.