Traditional research in scientific ecology, which is often satisfied by linearly projecting past trends into the future, can no longer account for the climatic or biological disorders observed today. Today, humanity is like a telluric force affecting major biogeophysical cycles and jeopardising the Earth system as a whole, and we cannot accurately predict the Earth's future path. The current Earth system is subject to global, objective, systemic, accelerated, anthropogenic, unpredictable and unregulated phenomena, phenomena characteristic of the Anthropocene. The social psychology that structures societies is partly an emergent phenomenon that occurs when individuals meet; it is also a generic process of their constitution, of human nature itself. In 2009 the 'green tides' in the bay of Saint-Michel-en-Greve even caused the death of a horse and rider due to asphyxiation by hydrogen sulphide fumes from decaying algae. Specular interaction leads to the impossibility of an early consensus on complex and controversial issues.