Resilience or resiliency is considered a critical property of adaptation for communities in the face of acute environmental, economic, and social change. In this context, resiliency can be described as the ability of a community to return to conditions that are functionally similar to pre-event conditions after a disturbance. Resiliency is often understood through three basic properties: 1) resistance, 2) response, and 3) recovery. Resistance is seen as the degree to which a system may withstand a shock such that it is not altered in the event of a disturbance. Response refers to how quicly and efficiently a system responds to a disturbance in the event that it does not withstand a shock. Recovery refers to the degree to which the system returns to pre-event conditions.
Resilience is related to the concept of stability, where a stable system is one that returns to its original state. A simple illustration here is to imagine a marble in a bowl. The blue marble (p1) sits in the bottom of the bowl. If pushed to position p2, the marble will quickly settle back at rest in the bottom of the bowl. Such a system would be considered stable. If the bowl is inverted so that the red marble rests on top of the outer convex surface it will quickly find itself in a new position (p2) where it will not return to its original position. In this case the system is considered unstable.
In nature, recovery often results in states that are functionally similar to pre-event conditions, though not necessarily organized as before the event, perhaps with assemblages of different species performing similar ecosystem functions.
Maguire and Hagan (2007) refer to an additional property, which they called "creativity," which suggests that highly adaptable human systems (e.g., communities) will seize opportunities to achieve higher functional states following perturbations. In position "a" of the figure at right, the system crashes, in "b" it has recovered to its original state, and in "c" it recovers to a higher functional state. For communities that are "overdeveloped" in certain functional areas to the degree of being vulnerable, it may be desirable to establish different functional states.
Some recent accounts in the field have suggested that resiliency should succeed sustainability as a more appropriate approach to managing communities. The view taken here is that resiliency is a fundamental property of sustainability and not a replacement for it.