What are bioindicators?

Bioindicators are species or biological conditions that assess ecosystem health. The role of bioindicators is to provide insights into the environmental quality and the functioning of ecosystems based on the presence, absence, or health of certain organisms. These organisms can include plants, animals, and microorganisms that are sensitive to changes in their environment, such as pollution or habitat alteration. For example, certain species of aquatic insects can indicate the quality of water in a stream; if these sensitive species are present, it often signifies a healthy ecosystem.

Endangered or near extinction species, while important to conservation, do not serve the broader purpose of measuring ecosystem health across different environmental conditions. Soil quality indicators are specific to terrestrial environments and do not encompass the wide range of biological assessments that bioindicators cover. Non-living elements used to measure pollution do not provide the biological context needed to evaluate ecosystem health, which relies on living organisms' responses to environmental conditions. Therefore, the correct answer accurately captures the essence of bioindicators as tools for assessing ecosystem health.