This is a specialised community of cyanobacteria, mosses, and lichens.
It works to improve soil stability, as well as offering increased resistance to wind and water erosion.
Crusts are often a feature of arid and semi-arid areas, where their sponge-y texture might also catch seed from nearby plants.
They have adapted to severe growing conditions but can easily be disturbed.
Disruption of the crusts brings decreased organism diversity, soil nutrients and stability.
Full recovery of crust from disturbance is a slow process, particularly for mosses and lichens.
Visual recovery can be complete in as little as one to five years, given average climate conditions.
However, recovering crust thickness can take up to 50 years, and mosses and lichens can take up to 250 years to recover.
