Environmental health indicators

Ecologists have proposed hundreds of quantitative indicators of the status of ecosystems for evaluation of and reporting on the status of marine ecosystems. The talk applies a common approach to classifying indicators, summarises the main properties of each class of indicator, and provides some illustrations. Indicators of ecosystem status have roles in both communication and decision support. For both roles, strengths. and weaknesses of indicators are usually only partially known. Few have been tested systematically for sensitivity and robustness across, a range of contexts... However, to determine best practices for selecting indicators for specific uses, one must have a fairly complete understanding of the information content of the various indicators. The paper explores some alternative approaches to documenting the information content of various indicators of ecosystem status. As the Precautionary Approach becomes broadly used as the basis for management decision-making, the role of indicators of ecosystem status,becomes central. The PA is made operational in decision-making through use of indicators and reference points. This means that it is necessary to identify values of an ecosystem indicator associated with harm to the environment that is serious or difficult to reverse. Methods for identifying and justifying reference points for ecosystem indicators are being developed and tested, but the task is turning out to be complex. Alternative strategies for identifying reference points are reviewed. When choices must be made from a suite of candidate indicators, it is desirable make the selection on objective grounds. This requires explicit a priori criteria, on which there is not yet scientific consensus. Recent developments in this area are reviewed, and again a way forward proposed. (C) 2003 Elsevier Science Ltd. All rights reserved.