Sustainability is a characteristic of a process or state that can be maintained at a certain level indefinitely. The term, in its environmental usage, refers to the potential longevity of vital human ecological support systems, such as the planet’s climatic system, systems of agriculture, industry, forestry, and fisheries, and human communities in general and the various systems on which they depend.
In recent years an academic and public discourse has led to this use of the word sustainability in reference to how long human ecological systems can be expected to be usefully productive. Observers point out that in the past, complex human societies have died out, sometimes as a result of their own growth and associated impacts on ecological support systems. The implication is that modern industrial society, which continues to grow in scale and complexity, might also collapse.
The implied preference would be for systems to be productive indefinitely, or be ‘sustainable.” For instance, “sustainable agriculture” would require agricultural systems expected to last indefinitely, “sustainable development” would be development of economic systems that last indefinitely, and so on. A side discourse relates the term sustainability to longevity of natural ecosystems and reserves (set aside for other-than-human species), but the greatest emphasis has been on human systems and anthropogenic problems, such as anthropogenic climate change, or the obviously anthropogenic depletion of fossil fuel reserves.