ABSTRACT
Indicators are depictions of system qualities, quantities or states, which are not directly accessible by the observer. Ecological indicators provide aggregated information on phenomena within human-environmental systems to characterize environmental management options. As the target of ecological indication is the provision of quantitative information for decision-making processes, ecosystem-based indicators have to represent the complex interactions between biotic and abiotic components. In general, good indicators should communicate information of high "scientific correctness" and high "practical applicability" with an optimal applicability. Considering the frequencies with which ecosystem service indicators are used in the literature, some basic trends are visible: regulating ecosystem services, especially global climate regulation and nutrient regulation, are the most frequently assessed services. One significant feature of approaches to ecosystem service indication is that single indicators are of limited use. Ecosystem service indicators are constructed to provide information for decision-making processes in human-environmental systems.
