Health metrics are determined by stakeholder goals, which drive ecosystem definition. An ecosystem is an abstraction.[28][29] “Ecosystems cannot be identified or found in nature. Instead, they must be delimited by an observer. This can be done in many different ways for the same chunk of nature, depending on the specific perspectives of interest.” [10]
Ecosystem definition determines the acceptable range of variability (reference conditions) and determines measurement variables. The latter are used as indicators of ecosystem structure and function, and can be used as indicators of “health.”