The concept of ‘resilience’ is one of the most important research topics in the context of achieving sustainability. Finding clear measures of resilience is a high priority for appropriate nature conservation and environmental management practices. Yet the measurement of resilience is elusive, as it is not possible to measure resilience directly. Rather, it must be estimated by resilience surrogates, i.e. indirect proxies that are derived from theory used in indicating resilience. Recently, the concept of ‘identity’ has been proposed as a proxy for estimating resilience. The application of identity to the concept of resilience, however, is still in its infancy.
To further this discussion, this paper revisits in a first step the methodology of self-identity proposed by Jax and colleagues. In contrast to the earlier attempts the methodology of self-identity emphasizes variables that can be easily operationalized. Those are: (a) if the ecosystem’s boundaries are defined topographically or functionally; (b) the expected internal degree of relationships; (c) the set of selected elements; and (d) the degree of component resolution. Principally, the last three criteria represent gradients and they can be arranged on axes and then assembled into a three-dimensional model which lays out a volume in which any ecological unit can be localized. The resulting SIC-model represents a very efficient way to explicitly communicate about an ecological unit that is focus of a particular study.

Results/Conclusions The methodology of self-identity is applied in a second step to the measurement of ecological resilience. Results show that a clear proxy of resilience can be gained by a three-step approach: (a) specification of the desirable self-identity (setting the baseline condition), (b) specification of the amount of change that would result in the loss of self-identity (identifying the bounds of desirability and bounds of undesirability), and (c) estimating the distance in state space from a system’s baseline condition to the bounds of undesirability (estimating the amount of ecological resilience). It turns out that the proxy for ecological resilience is a multivariate entity regarding the elements selected in a specific study. In addition, this proxy for resilience can be linked to disturbance scenarios. Ecological resilience is then pictured as the ability of an ecosystem to maintain its self-identity across various likely disturbance regimes. The self-identity approach to the measurement of ecological resilience can thus help in our quest for sustainable development.