The presence or absence of certain plant or other vegetative life in an ecosystem can provide important clues about the health of the environment: environmental preservation. There are several types of plant biomonitors, including mosses, lichens, tree bark, bark pockets, tree rings, and leaves. As an example, environmental pollutants can be absorbed and incorporated into tree bark, which can then be analyzed to pollutant presence and concentration in the surrounding environment. The leaves of certain vascular plants experience harmful effects in the presence of ozone, particularly tissue damage, making them useful in detecting the pollutant. These plants are observed abundantly in Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan. These regions with high endemic richness are particularly vulnerable to ozone pollution, emphasizing the importance of certain vascular plant species as valuable indicators of environmental health in terrestrial ecosystems. Conservationists use such plant bioindicators as tools, allowing them to ascertain potential changes and damages to the environment.  
As an example, Lobaria pulmonaria has been identified as an indicator species for assessing stand age and macrolichen diversity in Interior Cedar–Hemlock forests of east-central British Columbia, highlighting its ecological significance as a bioindicator. The abundance of Lobaria pulmonaria was strongly correlated with this increase in diversity, suggesting its potential as an indicator of stand age in the ICH. Another Lichen species, Xanthoria parietina, serves as a reliable indicator of air quality, effectively accumulating pollutants like heavy metals and organic compounds. Studies have shown that X. parietina samples collected from industrial areas exhibit significantly higher concentrations of these pollutants compared to those from greener, less urbanized environments. This highlights the lichen's valuable role in assessing environmental health and identifying areas with elevated pollution levels, aiding in targeted mitigation efforts and environmental management strategies. 
Fungi is also useful as bioindicators, as they are found throughout the globe and undergo noticeable changes in different environments.
Lichens are organisms comprising both fungi and algae. They are found on rocks and tree trunks, and they respond to environmental changes in forests, including changes in forest structure – conservation biology, air quality, and climate. The disappearance of lichens in a forest may indicate environmental stresses, such as high levels of sulfur dioxide, sulfur-based pollutants, and nitrogen oxides.
The composition and total biomass of algal species in aquatic systems serve as an important metric for organic water pollution and nutrient loading such as nitrogen and phosphorus.
There are genetically engineered organisms that can respond to toxicity levels in the environment; e.g., a type of genetically engineered grass that grows a different colour if there are toxins in the soil.