Drylands encompass 40% of Earth’s terrestrial surface and are set to increase under predicted climate models. In addition to being biodiversity hot-spots, they sustain large human populations and a range of key industries including agriculture, mining, and tourism. Inevitably, there is often a clash between maintaining ecological productivity and land degradation through continued economic use. Current rehabilitation strategies include the regulation of livestock, artificial enrichment of soils, and reinstatement of native vegetation. However, overlooked in these processes are the critical roles performed by microorganisms. Cyanobacteria are a globally distributed phylum of photosynthetic bacteria which, in drylands, form integral components of biocrusts - topsoil assemblages of microorganisms, mosses and lichens that stabilise the surface and enrich the soil profile. Able to tolerate extreme arid conditions while performing critical ecosystem services, biocrust cyanobacteria offer promising solutions to several hurdles currently limiting dryland rehabilitation. We seek to harness this potential in a multifaceted approach to improve restoration success rates.

Using next-generation sequencing, we have profiled biocrust microbiomes from across Australia and identified key cyanobacterial species involved in their formation and maintenance. Our datasets illustrate the natural status of biocrusts and help establish informed targets to assess and monitor topsoil recovery. Seasonality of precipitation was identified as a key factor affecting biocrust assembly on an intra-continental scale, indicating biocrust restoration will rely on employing locally-adapted, endemic cyanobacterial strains. In addition, we have isolated key biocrust species and have conducted novel microcosm experiments examining the effect of cyanobacteria on seedling establishment. We performed bio-priming of seeds with indigenous cyanobacteria and showed this had significant positive effects on the germination and seedling growth of Acacia hilliana and Senna notabilis, two native species used in restoration. Our work highlights the importance of cyanobacteria in drylands and is developing practical approaches for their integration with current rehabilitation strategies to enhance ecological outcomes.