Résumé
Although policy makers and managers are keen on scientific measures of ecosystem health, stability, resilience, resistance, productivity and other properties representing positive values, ecosystems are, by nature, open, dynamic and constantly changing. Ecosystem ecology tries to anticipate ecosystem structure, process and dynamics. Understanding ecosystems requires acknowledging the existence of fundamental limits and this is a major intuition of early ecologists. The Dust Bowl catastrophe suggested that rapid and massive soil erosion could result from the modifications in the interactions between soil, plants and atmosphere. The concept of an ecosystem removed the separation between the organic and the inorganic. Then, systems thinking, feedback loop mechanisms, energy flows, and cybernetics blurred the boundaries between natural phenomenon and techno-industrial objects. New aspects of biophysical reality are thus revealed: non-linearity, chaos and surprise, a few of the many restrictions to people's domination of Nature.