Lichens grow on all continents and have the ability to survive all altitudes and climates. In general, all lichens require time, undistributed surfaces and clean air to survive and thrive.
Lichens have a thallus body comprised of fungal symbiont, but there are several basic body types, including foliose lichens, crustose lichens, fruticose lichens and squamulose lichens. Foliose lichens have two-dimensional, leaf-like lobed thalli that are flat, and they grow in layers. Crustose lichens have a crust and form patches that are thick, rough and bright in color. Fruticose lichens are in three dimensions and are pendulous, and squamulose lichens are a mix between the crustose and foliose types.
Lichens play an important role in their ecosystems, and they help to establish life on sites that are barren and disturbed as well as on rocks. They aid in soil formation all over the planet and trap silt, dust and water as they colonize on rocks. Lichens convert air-based nitrogen into nitrates, which is an important part of the nitrogen cycle. This helps all plant life because during rainfall because nitrogen is pulled from dead and living lichens and all plant life that is nearby benefits from this. Upon their death, lichens enable vascular plant seeds and moss to develop.