Yet such single measures alone cannot predict survival, ecological health, or human use potential. Numerous factors must be considered together, within the context of often unique circumstances to produce an informed prediction. An important question at present is if we can define similar measurements and indices for human ecology and societal impact. Indices are ecosystem variables that are derived from data from both satellite and in-situ observations, as well as from process models. To whatever extent possible, such definitive data sets are being developed and integrated with broad application in mind.
Sustainability further incorporates the complexities of human action.
The sum of these complexities produces a virtually infinite set of possible states, both present and future. Clearly no single model can be constructed to adequately represent this, and furthermore not even the set of variables that might be used in such a model can be completely defined. Thus a virtually infinite set of indices can be derived from observational data and model runs. Without further knowledge, we may begin by assuming that those indices that are proven to be useful in more specific applications are the best candidates for assessing long-term sustainability.