James Lovelock and Lynn Margulis have formulated the Gaia hypothesis already in 1979, refering to the Greek Godess of the Earth. According to this hypothesis (or theory), the Earth is controling the conditions required for life throuh regulating mechanisms. The Earth is thus compared to a living organism, able to maintain homeostatic conditions. What can we think about such an hypothesis, about thirty years later? Even, if a number of conditions required for maintaining life, such as the salinity of the ocean, the atmosphere composition, the global surface temperature, appear as controlled by negative retroaction mechanisms (which tend to drive back the system towards equilibrium, when it is perturbated), it would be certainly wrong to apply such a comparison in a too litteral way. This hypothesis presents nevertheless the advantage of helping us to transform our mental representation system. During the industrial era all systems were viewed as machines, and we might be tempted to consider Earth as such a machine. The metaphor of the living organism is much more appropriate in the case of a complex ecosystem, as it helps us to understand better what happens when the system is perturbated. It leads us to think in terms of resilience. The system can withstand a perturbation within a certain domain. Outside this domain negative retroaction mechanisms do not operate anymore and can even be replaced by positive retroaction mechanisms which make the system unstable. The system cannot maintain its operating conditions (canot survive). This a situation we encounter with global warming. Therefore it is our duty to preserve and even to reinforce the resilience of Gaia.
Le chimiste britannique James Lovelock et la microbiologiste américaine Lynn Margulis ont formulé l'hypothèse Gaïa dès 1979. Cette hypothèse fait référence à la déesse mère de la mythologie grecque. Elle consiste à affirmer qu'à travers un certain nombre de mécanismes autorégulateurs, la Terre contrôle les conditions nécessaires à la survie de la biosphère. La Terre est ainsi comparée (ou assimilée) à un organisme vivant capable de maintenir des conditions homéostatiques.
