Lichens consist of a symbiotic partnership between fungi and algae or cyanobacteria. They do not fit neatly into any single trophic level. The algal or cyanobacterial component produces food through photosynthesis, making lichens primary producers. However, the fungal component absorbs nutrients and water from the environment, acting as a decomposer.

Additionally, lichens can also serve as food for various organisms, such as insects, birds, and mammals, occupying a position as primary consumers. Therefore, lichens can be considered multi-trophic organisms, fulfilling roles as primary producers, decomposers, and primary consumers.