Soil crust communities in semiarid and arid lands around the world hav
e received increasing attention in the past two decades. A symposium o
n their ecology was presented at the annual meeting of the American Br
yological and Lichenological Society held in 1991 in San Antonio, Texa
s. An introduction to the topic and an overview of the papers appearin
g in the proceedings volume are given in this prologue.