Dryland ecosystems cover over 40% of Earth's terrestrial landmass (1). Biocrusts—soil communities consisting of cyanobacteria, mosses, and lichens—can cover up to 70% of the ground in these ecosystems (see the figure, panel A) (2). The crucial role played by these and other very small organisms in nutrient, carbon, and water cycles has become increasingly clear in the past few decades (2, 3). Soil stability and the composition and performance of vascular plant communities also depend on biocrust health and activity. Yet, little is known about the identity, biology, ecophysiology, or distribution of the microbial components that dominate biocrusts (4, 5). Data are also needed to understand how they will respond to climate change. On page 1574 of this issue, Garcia-Pichel et al. (6) take a first step in filling this data gap.
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