The area covered by biocrusts - the algae, lichens, and mosses that currently cover 18 million km2 of soil across 12% of Earth’s total land surface - could decrease by about 25-40% by 2070 due to climate and land-use change, reports a study published online this week in Nature Geoscience.

Biological soil crusts, or biocrusts, are soil surface communities that help control the movement of water into soils and, by extension, affect nutrient cycling and local biodiversity. They also stabilise the soil surface, limiting dust generation. Biocrusts are mostly found in dry regions, where larger plants are not present to out-compete them.

Emilio Rodriguez-Caballero and colleagues looked at more than 500 previously published biocrust studies. They identified 18 different factors that make certain areas more suitable than others for forming biocrusts. Based on this classification, combined with climate and land-use projections, the authors infer a future decrease in the availability of land suitable for biocrust growth. Verifying their results with different models, they find that the area covered by biocrusts could decrease by up to 40% by 2070.