Final answer:
In conservation efforts, lichens are an example of an indicator species, which are organisms that reveal the health of an ecosystem through their presence or absence. This differs from keystone species, which play a central role in ecosystem structure, or invasive species, which threaten biodiversity.
Step-by-step explanation:
In conservation efforts, lichens are classified as an example of an indicator species. Indicator species are organisms that can give us clues about the health of an ecosystem. Because lichens are particularly sensitive to environmental changes, particularly air quality and climate, their presence or absence can indicate whether an ecosystem is healthy or suffering from pollution or other forms of environmental stress. Unlike keystone species, which have a central role in maintaining the structure of an ecological community, or invasive species, which can threaten native biodiversity, indicator species serve as a barometer for ecosystem health.The first species to live on new land, such as that formed from volcanic lava, are called pioneer species, which is different from keystone, indicator, or invasive species.