Indicator Species – What are they?

What does Indicator Species mean? 

An indicator species refers to an organism thats presence or absence in an ecosystem reflects the environmental conditions of the area it inhabits. For this reason, the abundance of indicator species are important conservation tools.

Indicator species can signal a change in the biological conditions of an ecosystem and this can help to identify any problems within an ecosystem and to determine its overall health.


Example of Indicator Species:

Lichens are a good example of what an indicator species is. Lichens are complex life-forms that are formed by a symbiotic relationship between two separate organisms; a fungus and an alga (cyanobacteria). Lichens grown in exposed areas like rocks and tree bark.

Lichens are good indicator species because they are very sensitive to environmental changes and pollutants within the environment. This species are very good at absorbing water and nutrients to grow in the environment. Rainwater has enough nutrients to keep them alive and well.

Any pollutants in the water or air will have a large effect on lichens and this allows conservationists and environmental scientists to identify the initial existence of a pollutant within the ecosystem at early stages. Therefore, lichens are indicator species for pollutants such as heavy metals and processes like eutrophication.

Relevant links: 

  • Lichens of Ireland –
  • What are lichens? –
  • Lichens as indicators –



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