Biological soil crusts are a complex of microscopic organisms growing on the soil surface in many arid and semi-arid ecosystems. These crusts perform the important role of stabilizing soil and reducing or eliminating water and wind erosion. One of the largest threats to biological soil crusts in the arid and semi-arid areas of the western United States is mechanical disturbance from vehicle traffic and grazing. The spread of the annual invasive cheatgrass has increased the fuel load in areas that previously would not carry a fire, posing a potentially widespread and new threat to this resource.
Recovery times for biological soil crusts are highly variable, and depend largely on the timing of disturbance and amount of moisture, with moisture hastening recolonization of crust organisms. Attempts to artificially restore biological soil crusts have been largely unsuccessful. However, crust organisms are airborne over short and long distances, and crusts can recover on their own when undisturbed and given time to reestablish.