The self-maintaining, self-renewing dynamic of nature as a system, including the life cycles constituted by the synthesis, use, and degradation of nitrogen, oxygen, carbon, sulphur [etc]. The 'balance' sustains the qualitative and quantitative needs of the sub-systems: the salt seas and fresh-water bodies, the forests, the soil, and the ecological relationships between the species. Man is the upsetter of the balance, engaged in this role for long centuries, but with ever increasing destabilizing power.
The process of evolution means that the pool of living diversity is dynamic: it increases when new genetic variation is produced, a new species is created or a novel ecosystem formed; it decreases when the genetic variation within a species decreases, a species becomes extinct or an ecosystem complex is lost. The concept emphasises the interrelated nature of the living world and its processes.