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Indicator is taken to mean a significant physical, chemical, biological, social or economic variable which can be measured in a defined way for management purposes. Some books give this meaning to the term attribute and an indicator is an aggregation of attributes related to the same issue.
A baseline tries to assess the behaviour of a system in the absence of some disturbing influence (a difficult task). For example, if the flow regime of a river were used as an indicator, the baseline would be the flow in the absence of any specified human influence (ie, without any dams, channels, weirs, or use of water). In most cases, the true baseline for natural systems cannot be defined or measured, so a particular condition at an agreed time is used as a substitute baseline. A benchmark (or threshold) is the value for an indicator that has some defined environmental significance in the functioning of the natural system. One example is the number and size of fish that can be harvested from a particular fishery without endangering the species' capacity to renew its numbers. Another is the concentration of pollutants that can be tolerated without damaging health. Whereas targets have a basis in policy and reflect human values, benchmarks are scientifically determined. Environment management is used here to include not only formal management processes but also a range of environment-related activities of individuals and groups and those interested in environment programs, policies and outcomes. The word environment is directed particularly to physical environmental factors, but in the understanding that their effective management must take account of social and economic factors. Environmental indicators are measures of physical, chemical, biological or socio-economic factors which best represent the key elements of complex ecosystems or environmental issues.
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