Legitimacy is the basis of informed consent to accept an agreed outcome by means that are judged to be accountable, fair, trusted and responsive to changing circumstances. Legitimacy is based on processes of governance that are inclusive and empowering, which increase resilience and reduce vulnerability in ecological and social realms.
Equity is the assurance that legitimate interests are identified, incorporated, and assisted to be included in the process of achieving agreed outcomes. Equity also addresses issues of justice in terms of human and ecological rights, as well as responsibilities for abiding by shared outcomes.
Efficiency is the condition that any decision taken must be one in which the consequent sustainability gains outweigh all the costs of implementation. That "benefit to cost" relationship, however, requires an integrated approach to participation and envisioning that explicitly incorporates the interests of the excluded as well as the connectivities of the natural world.
Effectiveness is that link to the natural world. Environmental decisions will only be effective if they are informed by natural-systems processes, variability, and change and its driving forces. Environmental decisions, therefore, need to buttress the resilience of those natural systems and ensure that human beings are not placed in a position whereby they undermine this resilience. Hence environmental effectiveness also means reducing social vulnerability as efficiently as possible.
Source: ESRC Programme on Environmental Decision Making (PEDM) (2001-2006)