It is defined variously in biological, economic and eco-social terms, all of which emphasize the ecological limits of Earth:
- by Natural Step as four specific "scientific" conditions
- by Mike Nickerson as eight requirements or obligations
- by the green ethic as a moral order placed on criteria to be used in choices
When properly used, the term refers ONLY to ecological, biosphere-wide feedback loops that do not result in positive feedback harmful to life itself. It is an ABUSE of the term to refer to "social sustainability" or "fiscal sustainability" although these are now both commonly heard. To dilute the ecological meaning is to compromise it, and cause it to fail as a marker of what is within the limits of ecosystems - if human society or economic systems must change or even fail to fit within those limits, they must and will fail. There is simply no negotiating what sustainability means with the biosphere. It is a limit that humans either live within, or fight for ever-scarcer resources within, or die fighting their planet.
In green economics sustainability is assumed as a given - that is, most green economics models a world where the comprehensive outcome of economic choice on the biosphere as a whole is considered in pricing and in laws.
By contrast, the eco-capitalist approaches assume that an organization that recognizes it as a constraint early achieves money, material, marketing and recruitment advantages (since it avoids various moral hazards) by adapting early to what is claimed to be an "inevitable" shift to full cost accounting in which deviations from global sustainability will generally be expensive.
Since any definition of sustainability depends on assumptions about the future, however, it is difficult to determine objectively.
The most credible methods of dealing with future uncertainty and regret in decision making tend to be those which backcast to a fixed time horizon - though other backcasting methodologies exist, e.g. in Natural Step), that do not apply such strict ((time horizon requirements.
Similarly, throughput accounting focuses on ratios of throughput to inventory, trying to reduce the latter while increasing the former. By using a broad definition of inventory that includes all capital assets, it likewise tends to reduce reliance on natural capital or infrastructural capital and so undo the tendency in most accounting to overfocus on labour savings. This may be a useful first step to sustainable models of throughput based on models of nature's services, which tend to be extraordinarily efficient in energy and material use, but also tend to take time, and are often labour-intensive for the living things involved.
The sustainability principle is one of the Six Principles of the Global Greens Charter. It was not one of the Four Pillars.
This is a refer link. This concept has no one authoritative definition. See the GFDL corpus article aten: wikipedia: sustainability for a general debate including more definitions.