Aerobiology and passive restoration of biological soil crusts

Biological soil crusts (BSCs) exist commonly on soil surfaces in many arid and semiarid areas, and disturbed soil surfaces in more mesic environments. BSCs perform many essential ecological functions. Substantial resources have been invested trying to restore or replace BSCs that have been damaged by anthropogenic disturbances, with various levels of success. The nexus of sciences related to BSC establishment and restoration, and to aerobiology suggests that crusts are established and re-established naturally via commonly occurring ecological processes. Formation of BSCs can be accelerated by implementing traditional or novel land rehabilitation techniques that create near-surface turbulence that facilitates the deposition of airborne BSC organisms. Sexual and asexual propagules of BSC organisms are found naturally in the atmosphere and are transported up to very long distances between continents and hemispheres. Whether restoration of BSCs occurs naturally in this fashion, or through efforts to produce and disseminate artificial inoculants, success is ultimately moderated and governed by the timing and frequency of adequate precipitation relative to the arrival of viable propagules on suitable substrates at appropriate times of year. For the greatest ecological and economic benefit, we suggest that efforts should focus on minimizing the scope and scale of unnecessary anthropogenic disturbance to BSC communities.