Ecology and functional roles of biological soil crusts in semi-arid ecosystems of Spain

► Biological soil crusts (BSCs) are key components, but historically understudied, of Spanish semi-arid ecosystems. ► We review the growing body of research on BSCs available from these ecosystems. ► BSCs are proving to be an excellent model system to foster new ways of thinking about key community and ecosystem ecology topics. ► The study of these organisms is opening new and highly promising research lines.