Biological indicators, also known as bioindicators or biomarkers, are organisms, species, or biological characteristics that we use to assess the health of an ecosystem, habitat, or the overall environment. These indicators can provide valuable information about the impact of various environmental factors, such as pollution, habitat degradation, and climate change.
We can measure changes in environmental conditions and understand the health and quality of an ecosystem.
Different types of biological indicators include:
Plants: Certain plants are sensitive to specific environmental conditions or pollutants. For example, we can use lichens to assess air quality.
Invertebrates: Insects, molluscs, and other invertebrates are bioindicators in freshwater and terrestrial ecosystems. The presence or absence of certain species may indicate the level of pollution or habitat quality.
Fish: We use fish as bioindicators in aquatic ecosystems. Changes in fish populations, growth rates, or behaviour can signal environmental stressors.
Birds: Birds can be bioindicators in various habitats. Their presence, breeding success, or migration patterns may reveal information about the health of an ecosystem.
Microorganisms: Microorganisms, such as bacteria and fungi, can be used as bioindicators, particularly in soil and water assessments.
Mammals: Certain mammal species also help understand larger terrestrial ecosystems.
Biological indicators provide a holistic approach to environmental monitoring, considering the complex interactions between different organisms and their environment. Monitoring bioindicator changes over time can help scientists and policymakers make informed decisions about environmental management and conservation strategies.
Sources
Sciencedirect – Biological indicators 
Nature.com – Bioindicators: Using Organisms to Measure Environmental Impacts
January 2024, RETHINK
