Biocrust restoration: a key tool to recover degraded arid ecosystem functioning

Biocrusts are autotroph and heterotroph communities that cover 12% of the Earth land's surface, where they act as ecosystem engineers. They are very vulnerable to climate change and disturbance caused by different anthropic activities. In this work, we revise the impacts of both disturbance types, which negatively affect biogeochemical cycles and water and energy balances, accelerate erosion processes and dust emissions, and decrease biodiversity, reducing ecosystem ability to provide services. We also explore the ability of these communities to recover after disturbance, which in general requires long time periods for the most developed communities. Because of this, new biotechnologies have emerged to accelerate their restoration, based on the inoculation of biocrust-forming organisms. Results from two main strategies according to the origin of the biocrust propagules used are revised: a) translocation of biocrust fragments from a donor area to the degraded area. This strategy is recommended for planned activities in which the existing biocrust before disturbance is applied: b) large-scale cultivation of bloc-rust-forming organisms (cyanobacteria, lichens, mosses or the whole community) in laboratory or greenhouse conditions for their later inoculation in the degraded area. Finally, we identify future challenges to maximize restoration success and biocrust conservation.