title: Evidence necessary for taxa to be reliable indicators of environmental conditions or impacts.
abstract: Using taxa as indicators of environmental impacts is widespread. Indicators are chosen because they are considered to be easy to measure, sensitive to stresses and respond to stresses in predictable ways. Here, we review these criteria by addressing the nature of the relationships between some characteristic of taxa and the environmental variables they are supposed to indicate. It is crucial that variables measured as indicators be strongly and consistently correlated (through space and time) with levels of the environmental variables. Appropriate experiments must be done to establish that an observed correlation is causal, or the correlation cannot be considered sufficient to identify a useful indicator. Finally, it is necessary to establish that the taxa directly respond to changes in the environmental variables they are supposed to indicate. Appropriate methodologies to establish these criteria are considered and we evaluate studies in which these criteria have or have not been met.
authors.affiliation: Centre for Research on Ecological Impacts of Coastal Cities, Marine Ecology Laboratories A11, University of Sydney, Sydney, NSW 2006, Australia. pgoodsell@eicc.bio.usyd.edu.au
authors.forename: P J
authors.initials: PJ
authors.lastname: Goodsell
authors.forename: A J
authors.initials: AJ
authors.lastname: Underwood
authors.forename: M G
authors.initials: MG
authors.lastname: Chapman
mesh_terms: D044822:Biodiversity; D003247:Conservation of Natural Resources / Q000379:methods*; D004777:Environment; D004784:Environmental Monitoring / Q000379:methods*