To characterize the condition of ecological receptors, national, state, and community-based environmental programs increasingly explored the use of ecological indicators.

Background of the demand for ecological indicators is the "Worldwide concern about environmental threats and sustainable development has led to increased efforts to monitor and assess status and trends in environmental condition. Environmental monitoring initially focused on obvious, discrete sources of stress such as chemical emissions. It soon became evident that remote and combined stressors, while difficult to measure, also significantly alter environmental condition. Consequently, monitoring efforts began to examine ecological receptors, since they expressed the effects of multiple and sometimes unknown stressors and their status was recognized as a societal concern."

An indicator is a sign or signal that relays a complex message, potentially from numerous sources, in a simplified and useful manner. An ecological indicator is defined here as a measure, an index of measures, or a model that characterizes an ecosystem or one of its critical components. An indicator may reflect biological, chemical or physical attributes of ecological condition. The primary uses of an indicator are to characterize current status and to track or predict significant change. With a foundation of diagnostic research, an ecological indicator may also be used to identify major ecosystem stress.

There are several paradigms currently available for selecting an indicator to estimate ecological condition. They derive from expert opinion, assessment science, ecological epidemiology, national and international agreements, and a variety of other sources (see Noon 1998, Anonymous 1995, Cairns et al. 1993, Hunsaker and Carpenter 1990, and Rapport et al. 1985). The chosen paradigm can significantly affect the indicator that is selected and is ultimately implemented in a monitoring program. One strategy is to work through several paradigms, giving priority to those indicators that emerge repeatedly during this exercise.

Under EPA’s Framework for Ecological Risk Assessment (EPA 1992), indicators must provide information relevant to specific assessment questions, which are developed to focus monitoring data on environmental management issues. The process of identifying environmental values, developing assessment questions, and identifying potentially responsive indicators is presented elsewhere (Posner 1973, Bardwell 1991, Cowling 1992, Barber 1994, Thornton et al. 1994). Nonetheless, the importance of appropriate assessment questions cannot be overstated; an indicator may provide accurate information that is ultimately useless for making management decisions. In addition, development of assessment questions can be controversial because of competing interests for environmental resources. However important, it is not within the purview of this document to focus on the development and utility of assessment questions. Rather, it is intended to guide the technical evaluation of indicators within the presumed context of a pre-established assessment question or known management application

Numerous sources have developed criteria to evaluate environmental indicators. This document assembles those factors most relevant to ORD-affiliated ecological monitoring and assessment programs into 15 guidelines and, using three ecological indicators as examples, illustrates the types of information that should be considered under each guideline. This format is intended to facilitate consistent and technically-defensible indicator research and review. Consistency is critical to developing a dynamic and iterative base of knowledge on the strengths and weaknesses of individual indicators; it allows comparisons among indicators and documents progress in indicator development. ...



Projects in relation to ecological indicators: