In recent decades, ecosystem theory has revisited the meaning of human action. There is a growing tendency to recognize that, once “left alone”, human modified ecosystems do not return to their primitive state. Recently, this notion has been radically advocated by a group of ecologists who propose the concept of “emerging” or “novel” ecosystems. Emerging ecosystems are the direct result of either intense human modification of preserved ecosystems or the abandonment of established land uses (crops, pastures, planted forests etc.). These ecosystems present locally unprecedented patterns of species composition and dominance that don’t depend on human intervention for its maintenance. Therefore these novel ecosystems “exist as a non-regressive consequence of human activity”.