Surrogate biodiversity indicators may be used to quantify ecosystem status or potential habitat suitability where it is too complex or expensive to measure biodiversity components directly. They may also be particular species (groups) that are used to represent biodiversity in general.
Surrogate indicators for biodiversity are biotic or abiotic environmental variables that represent, or are closely related to, the biodiversity components of interest. In practical terms, surrogate indicators should also be easier and less expensive to measure than the biodiversity components they represent.
Examples of such surrogate indicators are certain flagship or umbrella species whose presence may tell us something about the quality of the habitat or the ecosystem. Coarse woody debris in boreal forests is often considered as an important surrogate indicator for forest ecosystem integrity as well as the species richness of intact forest ecosystems. In freshwater ecosystems, simple chemical variables for acidity or nutrient loads may be used to measure water quality and may also be considered as useful surrogate indicators of ecosystem integrity.